MDCAT 2023 Chemistry

MDCAT 2023 Chemistry Past Paper MCQs with Answers

196 Chemistry MCQs that appeared in MDCAT 2023, arranged unit by unit in syllabus order. Tap “Show answer” under any question for the correct option and a short solution.

Fundamental Concepts of Chemistry

1.One a. m .u stands for (UHS MDCAT 2023)

  1. An atom of C - 12
  2. 1/12th of a carbon
  3. 1/12th of H
  4. 1 atom of all the elements
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Correct answer: (b) 1/12th of a carbon

One atomic mass unit is a twelfth of the mass of an atom of carbon-12.

2.A compound of sodium oxide has 74.2 % sodium and 25.8% of Oxygen. The empirical formula of the compound is? (UHS MDCAT 2023)

  1. NaO
  2. NaO2
  3. Na2O
  4. Na2O2
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Correct answer: (c) Na2O

Dividing by the atomic masses gives $3.23$ of sodium to $1.61$ of oxygen, a ratio of two to one.

3.For the reaction given below: N2 + 3H2 ⇌ 2NH3 How many moles N2 are required for synthesis of 4 moles of NH3? (SZABMU MDCAT 2023)

  1. 4 moles of N2
  2. 2 moles of N2
  3. 3 moles of N2
  4. 4.5 moles
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Correct answer: (b) 2 moles of N2

The equation gives two moles of ammonia for each mole of nitrogen.

4.Al reacts with O2 according to the following reaction: 4Al + 3O2 ⟶ 2Al2O3 27g of Al will react with how much of O2? (SZABMU MDCAT 2023)

  1. 8 g
  2. 16 g
  3. 24 g
  4. 32 g
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Correct answer: (c) 24 g

$27\,\mathrm{g}$ is one mole of aluminium, which needs three quarters of a mole, $24\,\mathrm{g}$, of oxygen.

5.One mole of a substance is the amount of that substance that has the same number of particles (atom, ions or molecules) as there are atoms in exactly: (SZABMU MDCAT 2023)

  1. 1.008 g of hydrogen gas (H2)
  2. 16 g of oxygen gas (O2)
  3. 12 g of carbon-12 isotopes
  4. 12 g of magnesium
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Correct answer: (c) 12 g of carbon-12 isotopes

The mole is defined by the number of atoms in exactly $12\,\mathrm{g}$ of carbon-12.

6.What is the mass of sulphur in 24.5 g of H2SO4? (NUMS MDCAT 2023)

  1. 32 g
  2. 24 g
  3. 16 g
  4. 8 g
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Correct answer: (d) 8 g

$24.5\,\mathrm{g}$ is a quarter of a mole, and a quarter of $32\,\mathrm{g}$ of sulphur is $8\,\mathrm{g}$.

7.From the equation (N2 + 3H2 → 2NH3), how many moles of NH3 are produced from 2.5 moles of N2? (NUMS MDCAT 2023)

  1. 2.5 moles
  2. 2 moles
  3. 5 moles
  4. 7.5 moles
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Correct answer: (c) 5 moles

Each mole of nitrogen gives two of ammonia, so $2.5$ moles give $5$.

8.The average weight of atoms of an element compared to the weight of one atom of _________ is called atomic weight. (UHS MDCAT 2023)

  1. Carbon
  2. Helium
  3. Hydrogen
  4. Nitrogen
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Correct answer: (a) Carbon

Atomic weights are referred to carbon-12, taken as exactly twelve units.

9.Which element is used as standard to determine atomic mass of an element? (UHS MDCAT 2023)

  1. H
  2. C
  3. P
  4. Cl
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Correct answer: (b) C

Carbon-12 is the standard against which atomic masses are measured.

10.30 grams of 2-propanol were mixed with excess acidified K2Cr2O7 and boiled under reflux for 20 minutes. The organic product was then collected by distillation. The yield of product was 75.0%. What is the mass of product produced? (UHS MDCAT 2023)

  1. 1.74g
  2. 21.75g
  3. 2.74g
  4. 29.9 g
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Correct answer: (b) 21.75g

Half a mole of the alcohol would give half a mole, $29\,\mathrm{g}$, of acetone, and three quarters of that is $21.75\,\mathrm{g}$.

Atomic Structure

11.Which gas in the discharge tube produces lightest canal ray particles? (UHS MDCAT 2023)

  1. Ar
  2. He
  3. H2
  4. Ne
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Correct answer: (c) H2

Canal rays are positive ions of the gas, and the hydrogen ion is the lightest of all.

12.The amount of energy associated with quantum of radiation is directly proportional to: (NUMS MDCAT 2023)

  1. Photon
  2. Wavelength
  3. Frequency
  4. Velocity
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Correct answer: (c) Frequency

A quantum carries energy $hf$, proportional to the frequency.

13.Principle quantum number is represented by the symbol: (SZABMU MDCAT 2023)

  1. m
  2. n
  3. s
  4. l
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Correct answer: (b) n

The principal quantum number is $n$.

14.Shape of the sub shell is explained by which quantum number: (SZABMU MDCAT 2023)

  1. Principal quantum number
  2. Azimuthal quantum number
  3. Magnetic quantum number
  4. Spin quantum number
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Correct answer: (b) Azimuthal quantum number

The azimuthal quantum number $l$ fixes the shape of the subshell.

15.Maximum number of electrons which can be placed in one orbital is: (SZABMU MDCAT 2023)

  1. 1
  2. 2
  3. 3
  4. 4
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Correct answer: (b) 2

No two electrons may share all four quantum numbers, so an orbital holds two of opposite spin.

16.If value of azimuthal quantum number is 2 then total values of magnetic quantum number will be: (NUMS MDCAT 2023)

  1. 03
  2. 05
  3. 07
  4. 10
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Correct answer: (b) 05

With $l=2$ the magnetic quantum number runs from $-2$ to $+2$, five values in all.

17.Which of the following quantum number is not obtained from Schrodinger Wave equation? (NUMS MDCAT 2023)

  1. Principal Quantum Number
  2. Spin Quantum Number
  3. Azimuthal Quantum Number
  4. Magnetic Quantum Number
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Correct answer: (b) Spin Quantum Number

The wave equation gives $n$, $l$ and $m$; the spin quantum number was added to account for the doubling of lines.

18.According to which scientist, the probability of finding an electron at a certain position is possible? (UHS MDCAT 2023)

  1. Bohr's
  2. De-Broglie
  3. Hund's
  4. Schrodinger
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Correct answer: (d) Schrodinger

Schrodinger’s wave equation gives the probability of finding the electron in a region of space.

19.Total number of directions of f-orbitals in space are: (NUMS MDCAT 2023)

  1. 05
  2. 03
  3. 07
  4. 06
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Correct answer: (c) 07

There are seven f orbitals in a subshell.

20.When the $6d$ orbital is filled, the entering electron goes into: (MDCAT 2023)

  1. $7s$
  2. $7p$
  3. $8s$
  4. $5f$
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Correct answer: (b) $7p$

By the $(n+l)$ rule the next lowest set after $6d$ is $7p$.

21.Which element has the ground state electronic configuration $1s^2\,2s^2\,2p^6\,3s^2\,3p^6$? (MDCAT 2023)

  1. Cl
  2. K
  3. Ne
  4. Ar
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Correct answer: (d) Ar

Eighteen electrons in a closed shell arrangement is argon.

22.What is the proton number of the element that has four unpaired electrons in its ground state? (MDCAT 2023)

  1. 24
  2. 25
  3. 22
  4. 26
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Correct answer: (d) 26

Iron, $[\mathrm{Ar}]3d^64s^2$, has four unpaired $3d$ electrons.

23.Which element has the ground state electronic configuration of 1s2, 2s2, 2p6, 3s2, 3p6? (UHS MDCAT 2023)

  1. Ar
  2. Cl
  3. Na
  4. S
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Correct answer: (a) Ar

Eighteen electrons filled to $3p^6$ is argon.

24.What is the proton (atomic number) of an element that has four unpaired electrons in its ground state? (UHS MDCAT 2023)

  1. 6
  2. 14
  3. 22
  4. 26
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Correct answer: (d) 26

Iron, $[\mathrm{Ar}]3d^6 4s^2$, has four unpaired d electrons.

25.The electronic configuration for degenerated orbitals is explained by: (SZABMU MDCAT 2023)

  1. Aufbau Principle
  2. 𝑛 + 𝑙 rule
  3. Hund’s rule
  4. Pauli exclusion principle
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Correct answer: (c) Hund’s rule

Hund’s rule fills degenerate orbitals singly before any is doubled.

26.The electronic configuration for degenerate orbitals is explained by: (NUMS MDCAT 2023)

  1. Aufbau Principle
  2. n + l rule
  3. Hund's rule
  4. Pauli exclusion principle
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Correct answer: (c) Hund's rule

Hund’s rule fills degenerate orbitals singly before any is doubled.

27.When 6d orbital is filled, the entering electron goes into? (UHS MDCAT 2023)

  1. 7f
  2. 7d
  3. 7p
  4. 7s
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Correct answer: (c) 7p

By the $n+l$ rule the 7p subshell follows the 6d.

Gases

28.The process of heat flow between hotter and colder bodies stops when their molecules have equal: (MDCAT 2023)

  1. average translational kinetic energy
  2. average rotational kinetic energy
  3. average translational potential energy
  4. average vibrational kinetic energy
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Correct answer: (a) average translational kinetic energy

Temperature is a measure of the average translational kinetic energy, and heat flows until the two are equal.

29.The process of heat flow between hotter and colder gases remains continued until all the molecules have equal (UHS MDCAT 2023)

  1. Average translational kinetic energy
  2. Average rotational kinetic energy
  3. Average translational potential energy
  4. Average vibrational kinetic energy
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Correct answer: (a) Average translational kinetic energy

Temperature is a measure of the mean translational kinetic energy, so heat flows until those are equal.

30.Air is a mixture of gases. The molecules of air do notsettle down due to: (SZABMU MDCAT 2023)

  1. Different molar mass
  2. Non polar nature of gases
  3. Presence of dust particles in air
  4. Elastic collision of gas molecules
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Correct answer: (d) Elastic collision of gas molecules

The molecules keep their energy through collisions, so they stay in ceaseless motion and never settle.

31.Collision shown by gases involve the following: (SZABMU MDCAT 2023)

  1. No energy change
  2. No pressure change
  3. Small energy change
  4. Large energy change
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Correct answer: (a) No energy change

Gas collisions are perfectly elastic, so no kinetic energy is lost in them.

32.The idea that molecules in gases are in constant movement is called: (NUMS MDCAT 2023)

  1. Kinetic theory of gases
  2. Crystal field theory
  3. Molecular orbital theory
  4. Transition state theory
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Correct answer: (a) Kinetic theory of gases

That is the kinetic molecular theory of gases.

33.The SI unit for pressure is: (NUMS MDCAT 2023)

  1. mm of Hg
  2. Pascal
  3. Bar
  4. Torr
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Correct answer: (b) Pascal

The SI unit of pressure is the pascal, a newton per square metre.

34.According to Charles law volume of gas reduces to zero at: (SZABMU MDCAT 2023)

  1. -12 O C
  2. 0 O C
  3. -273.15 O C
  4. -210 O C
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Correct answer: (c) -273.15 O C

Extrapolating the volume line to zero gives $-273.15^{\circ}\mathrm{C}$.

35.A gaseous mixture contains 9.6% NH3, 22.6% N2 and 67.8% H2 gases. If the total pressure is 50 atm, then the partial pressure of H2 is (UHS MDCAT 2023)

  1. 67.8 x100 / 50
  2. 50 x 100 / 100
  3. 67.8 x 50 / 100
  4. 67.8 + 50 / 100
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Correct answer: (c) 67.8 x 50 / 100

A partial pressure is the mole fraction times the total, that is $67.8\times50/100$.

36.If both temperature and volume of gas are doubled, the pressure: (NUMS MDCAT 2023)

  1. Cannot be predicted
  2. Is reduced to 1⁄2
  3. Remains unchanged
  4. Is doubled
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Correct answer: (c) Remains unchanged

$P=nRT/V$, and doubling both the temperature and the volume leaves the ratio unchanged.

37.Which one of the following gases has the lowest density under room conditions? (UHS MDCAT 2023)

  1. Neon
  2. Nitrogen
  3. Oxygen
  4. Fluorine
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Correct answer: (a) Neon

Density goes with molar mass at a given temperature and pressure, and neon has the smallest of these.

38.If we want to raise the temperature of one mole of an ideal gas by one kelvin, we have to provide how much amount of energy? (UHS MDCAT 2023)

  1. 0.0821 joules
  2. 8.314 dm3·atm
  3. 0.0821 kJ
  4. 0.0821 dm3·atm
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Correct answer: (d) 0.0821 dm3·atm

That energy is the gas constant, $0.0821\,\mathrm{dm^3\,atm\,mol^{-1}\,K^{-1}}$.

Liquids

39.Which type of forces exist between iodine molecules? (MDCAT 2023)

  1. dipole-dipole forces
  2. dipole-induced dipole forces
  3. instantaneous dipole-induced dipole forces
  4. hydrogen bonding
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Correct answer: (c) instantaneous dipole-induced dipole forces

Iodine is non-polar, so only London dispersion forces hold its molecules together.

40.In liquid, with the change in dipole-dipole forces, there is a change in some physical properties. Select the property which is not affected by the strength of dipole-dipole forces? (UHS MDCAT 2023)

  1. boiling point
  2. heat of vaporization
  3. heat of sublimation
  4. moles
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Correct answer: (d) moles

The number of moles is fixed by how much substance there is, not by the forces between its molecules.

41.Which of the following has highest surface tension? (SZABMU MDCAT 2023)

  1. Benzene
  2. Alcohols
  3. Ether
  4. Water
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Correct answer: (d) Water

Water is held by hydrogen bonds, which gives it much the greatest surface tension of these.

42.Which of the following has highest boiling point? (SZABMU MDCAT 2023)

  1. C4H10
  2. C6H14
  3. C10H22
  4. C2H6
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Correct answer: (c) C10H22

The longest chain has the largest surface for its dispersion forces, so decane boils highest.

43.The boiling point of ether is less as compared to alcohols and phenols due to: (NUMS MDCAT 2023)

  1. Functional group
  2. Intermolecular forces
  3. Nature of alkyl groups
  4. Isomerism
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Correct answer: (b) Intermolecular forces

An ether has no hydroxyl hydrogen, so it cannot hydrogen bond as an alcohol or a phenol does.

44.Which is not a property of liquid? (UHS MDCAT 2023)

  1. Osmotic pressure
  2. Freezing point
  3. Diffusion
  4. Melting
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Correct answer: (d) Melting

Melting is what a solid does; a liquid boils or freezes.

45.Which of the following factor does not affect the magnitude of vapor pressure? (UHS MDCAT 2023)

  1. amount of liquid
  2. size of molecule
  3. temperature of liquid
  4. intermolecular forces
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Correct answer: (a) amount of liquid

Vapour pressure is a property of the liquid at a given temperature, whatever quantity of it there is.

46.Vapor pressure is independent of which factor? (NUMS MDCAT 2023)

  1. Temperature
  2. Intermolecular forces
  3. Density of liquid
  4. Surface area of liquid
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Correct answer: (d) Surface area of liquid

Vapour pressure is a property of the liquid at a given temperature, whatever area is exposed.

47.When two ice cubes are pressed over each other, they unite to form one cube due to: (SZABMU MDCAT 2023)

  1. Dipole dipole attraction
  2. Covalent attraction
  3. Van Der Waal's forces
  4. H - bonding
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Correct answer: (d) H - bonding

The pressure melts a film of water, which freezes again as hydrogen bonds form across the join.

48.The strongest hydrogen bond is present in: (SZABMU MDCAT 2023)

  1. H2S
  2. HF
  3. H2O
  4. NH3
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Correct answer: (b) HF

Fluorine is the most electronegative, so the hydrogen bond in hydrogen fluoride is the strongest.

49.When 2 ice cubes are pressed over each other they unite to form one cube due to: (NUMS MDCAT 2023)

  1. Dipole dipole attraction
  2. Covalent attraction
  3. Van Der Waal's forces
  4. H-bonding
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Correct answer: (d) H-bonding

The pressure melts a film of water, which freezes again as hydrogen bonds form across the join.

50.Ice floats on the surface of water due to: (SZABMU MDCAT 2023)

  1. Larger bond length
  2. Cubic structure of ice
  3. Weak intermolecular forces
  4. Empty spaces in the structure of ice
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Correct answer: (d) Empty spaces in the structure of ice

Hydrogen bonds hold the molecules of ice in an open lattice with spaces in it, so ice is less dense than water.

Solids

51.Q.82 Which type of solid is called as atomic solid? (UHS MDCAT 2023)

  1. Covalent solids
  2. Ionic solids
  3. Metallic solids
  4. Molecular solids
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Correct answer: (c) Metallic solids

A metal crystal is built of atoms in a sea of electrons, so it is called an atomic solid.

52.The molecules of iodine (I2) form the: (SZABMU MDCAT 2023)

  1. Molecular crystals
  2. Covalent crystals
  3. Ionic crystals
  4. Metallic crystals
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Correct answer: (a) Molecular crystals

Iodine molecules are held in the lattice by weak dispersion forces, so the crystal is molecular.

53.The type of bonding in Zinc is: (SZABMU MDCAT 2023)

  1. Ionic
  2. Covalent
  3. Dative
  4. Metallic
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Correct answer: (d) Metallic

Zinc is a metal, its atoms held by a sea of delocalized electrons.

54.Thermal conductivity of metals is due to: (NUMS MDCAT 2023)

  1. Layered structure of metals
  2. Freely moving electrons
  3. Loosely held metal atoms
  4. Vibrational movement of metals
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Correct answer: (b) Freely moving electrons

The delocalized electrons carry the energy quickly through the metal.

55.Which of the following substance is malleable and ductile? (NUMS MDCAT 2023)

  1. Sodium chloride
  2. Copper sulphate
  3. Mercury
  4. Aluminum
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Correct answer: (d) Aluminum

A metal can be beaten into sheets and drawn into wire because its layers slide without breaking the bonding.

56.In anisotropic crystals which property do not change with the change in direction of crystalline structure? (UHS MDCAT 2023)

  1. Electrical conductance
  2. Thermal conductance
  3. Molar mass
  4. Refractive index
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Correct answer: (c) Molar mass

Anisotropy is about properties measured along a direction; the molar mass has no direction.

57.In metals, why electric conductivity decreases with the increase of temperature? (UHS MDCAT 2023)

  1. Because electron movement decrease with the increase of temperature
  2. Because metal ions oscillations hinder electron movement
  3. Because electron direction changes at high temperature
  4. Because they pass heat current through collision of electrons
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Correct answer: (b) Because metal ions oscillations hinder electron movement

Heating makes the ions vibrate more widely, and the electrons are scattered by them.

58.Q.81 A small building block which belongs to whole information about crystal structure is called? (UHS MDCAT 2023)

  1. Cell
  2. Unit Cell
  3. Crystal lattice
  4. Crystal unit
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Correct answer: (b) Unit Cell

The unit cell is the smallest block that carries the whole pattern of the crystal.

59.Which statement correctly describes the structure of sodium chloride crystal? (NUMS MDCAT 2023)

  1. Each sodium ion is surrounded by six chloride ions and each chloride ions surrounded by six sodium ions
  2. The crystal is face centered cubic structure
  3. Each sodium ion is surrounded by 3 chloride ions and each chloride ion surrounded by 3 sodium ions
  4. Inter molecular forces are present between two oppositely charges ions
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Correct answer: (a) Each sodium ion is surrounded by six chloride ions and each chloride ions surrounded by six sodium ions

Each ion in rock salt is at the centre of an octahedron of six of the other kind.

60.Co-ordination number of Na is: (NUMS MDCAT 2023)

  1. 10
  2. 9
  3. 8
  4. 12
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Correct answer: (c) 8

Sodium is body centred cubic, so each atom has eight nearest neighbours.

61.The greater Lattice energy is shown by: (NUMS MDCAT 2023)

  1. NaCl
  2. NaBr
  3. NaI
  4. NaF
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Correct answer: (d) NaF

Lattice energy is greatest for the smallest ions, and fluoride is the smallest halide.

62.Equation represents which energy change? Mg2+(g) + O2−(g) → MgO(s) (NUMS MDCAT 2023)

  1. Atomization
  2. Neutralization
  3. Lattice energy
  4. Solution
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Correct answer: (c) Lattice energy

Gaseous ions coming together into one mole of the solid release the lattice energy.

Chemical Equilibrium

63.Chemical equilibrium is: (MDCAT 2023)

  1. the end of the reaction
  2. the complete consumption of the reactants
  3. the complete consumption of the products
  4. a state at which there is no net concentration change
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Correct answer: (d) a state at which there is no net concentration change

Both reactions continue at equal rates, so the concentrations stop changing without the reaction stopping.

64.By which of the following factors equilibrim state is attained earlier? (SZABMU MDCAT 2023)

  1. Temperature
  2. Pressure
  3. Concentration
  4. Catalyst
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Correct answer: (d) Catalyst

A catalyst speeds both directions equally, so equilibrium is reached sooner without being shifted.

65.By which of the following factors equilibrium state is attained earlier? (NUMS MDCAT 2023)

  1. Temperature
  2. Pressure
  3. Concentration
  4. Catalyst
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Correct answer: (d) Catalyst

A catalyst speeds both directions equally, so equilibrium comes sooner without moving.

66.What is the ultimate fate of reversible reaction? (UHS MDCAT 2023)

  1. Completion of reaction
  2. Complete consumption of reactants
  3. Complete consumption of products
  4. A state when there is no net concentration change
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Correct answer: (d) A state when there is no net concentration change

A reversible reaction ends in equilibrium, where the concentrations no longer change.

67.One can estimate the direction in which an equilibrium will shift with the help of: (MDCAT 2023)

  1. Le Chatelier's principle
  2. the law of mass action
  3. Hess's law
  4. the law of heat of formation
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Correct answer: (a) Le Chatelier's principle

Le Chatelier's principle says the system shifts so as to oppose the change imposed on it.

68.Q.85 One can estimate the direction in which equilibrium will shift with the help of: (UHS MDCAT 2023)

  1. Le Chatelier's principle
  2. Law of mass action
  3. Mess's law
  4. Law of heat of formation
Show answer

Correct answer: (a) Le Chatelier's principle

Le Chatelier’s principle says which way an equilibrium moves when it is disturbed.

69.In reversible reaction, when product is removed, the equilibrium shift towards the: (UHS MDCAT 2023)

  1. Reactant side
  2. Product side
  3. Both side one by one
  4. No effect
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Correct answer: (b) Product side

Taking the product away drives the equilibrium forward to replace it.

70.Q.84 The precipitation occurs if the ionic concentration is: (UHS MDCAT 2023)

  1. Less than ksp
  2. More than ksp
  3. Equal to ksp
  4. Present in any amount
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Correct answer: (b) More than ksp

A solid comes down once the ionic product exceeds the solubility product.

71.Q.83 The decrease in solubility of the salt in a solution that already contains an ion common to that salt is known as: (UHS MDCAT 2023)

  1. Le Chatelier's principle
  2. Solubility Product
  3. Common ion effect
  4. Ksp
Show answer

Correct answer: (c) Common ion effect

Adding a common ion drives the dissolution equilibrium back, which is the common ion effect.

72.Which of the following is not the use of Buffer solution? (SZABMU MDCAT 2023)

  1. Used for the caliberation of pH meters
  2. Used to preserve biologicalspecimen
  3. Maintain the pH of the human blood
  4. Predict the concentration of a substance
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Correct answer: (d) Predict the concentration of a substance

A buffer holds a pH steady; it measures no concentration.

73.For the chemical reaction: N2(g) + 3H2(g) ⇌ 2NH3(g) + Heat We can get maximize the yield of NH3: (SZABMU MDCAT 2023)

  1. By increasing the temperature
  2. By decreasing the pressure
  3. By increasing the volume of the reaction vessel
  4. By continuous withdrawal of ammonia after intervals
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Correct answer: (d) By continuous withdrawal of ammonia after intervals

Taking the ammonia away as it forms keeps drawing the equilibrium forward.

74.The high pressure of 200 atm in Haber’s process is used for: (SZABMU MDCAT 2023)

  1. Better yield
  2. Lower yield
  3. Lower rate
  4. Cost decrease
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Correct answer: (a) Better yield

The forward reaction contracts from four molecules to two, so pressure favours it.

Reaction Kinetics

75.The rate of reaction between two specific time intervals is called the: (MDCAT 2023)

  1. instantaneous rate of reaction
  2. rate of reaction
  3. average rate of reaction
  4. specific rate of reaction
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Correct answer: (c) average rate of reaction

A change measured over an interval rather than at an instant is the average rate.

76.What is incorrect about activated complex? (SZABMU MDCAT 2023)

  1. It is a high energy specie
  2. It is a stable specie
  3. It is an unstable specie
  4. Potentia energy is maximum at activated complex stage
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Correct answer: (b) It is a stable specie

The activated complex sits at the top of the energy barrier and is therefore unstable.

77.The minimum amount of energy required by the colliding particles for effective collisions is called: (NUMS MDCAT 2023)

  1. Activation energy
  2. Lattice energy
  3. Bond energy
  4. Hydration energy
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Correct answer: (a) Activation energy

That least energy is the activation energy.

78.How will be the rate of reaction, if the slope of the curve is greater near the start of the reaction? (UHS MDCAT 2023)

  1. Constant
  2. Equilibrium
  3. Greater
  4. Lesser
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Correct answer: (c) Greater

The slope of the concentration time curve is the rate, so a steep slope means a fast reaction.

79.The rate of reaction between two specific time intervals is called? (UHS MDCAT 2023)

  1. Instantaneous rate of reaction
  2. Rate of reaction
  3. Average rate of reaction
  4. Initial rate
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Correct answer: (c) Average rate of reaction

A rate measured over an interval rather than at an instant is the average rate.

80.Q.87 The catalysis in which the catalyst and the reactants are in the same phase is known? (UHS MDCAT 2023)

  1. Heterogeneous catalyst
  2. Homogeneous catalyst
  3. Slow
  4. Fast
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Correct answer: (b) Homogeneous catalyst

A catalyst in the same phase as the reactants is a homogeneous catalyst.

81.When temperature of reacting gases is raised by 10 K, the reaction rate will increase to: (NUMS MDCAT 2023)

  1. Double
  2. Three times
  3. Four times
  4. Five times
Show answer

Correct answer: (a) Double

As a rough rule the rate doubles for every ten kelvin rise.

82.Q.86 What is the overall order of this rate equation? Rate =k[H3][NO2]2 (UHS MDCAT 2023)

  1. 1
  2. 2
  3. 3
  4. 4
Show answer

Correct answer: (c) 3

The overall order is the sum of the powers, $1+2$, that is three.

83.If a reaction is first order with respectd to a reactant then the rate will be__________if the concentration of reactant is doubled: (SZABMU MDCAT 2023)

  1. Doubled
  2. Halved
  3. One fourth
  4. Quadrupled
Show answer

Correct answer: (a) Doubled

First order means the rate is proportional to that concentration.

84.When nitric oxide reacts with ozone, the order of reaction will be: (NUMS MDCAT 2023)

  1. 2nd
  2. 3rd
  3. 1st
  4. Zero
Show answer

Correct answer: (a) 2nd

The reaction is first order in each reactant, so second order overall.

85.The unit of rate constants is the same as the rate of reaction in which of the following order of reaction? (SZABMU MDCAT 2023)

  1. Zero
  2. First
  3. Second
  4. Third
Show answer

Correct answer: (a) Zero

For a zero order reaction the rate equals $k$, so the two have the same unit.

Thermochemistry and Energetics of Chemical Reactions

86.Q.89 Which of the following term is state function? (UHS MDCAT 2023)

  1. freezing
  2. decomposition
  3. sublimation
  4. enthalpy
Show answer

Correct answer: (d) enthalpy

Enthalpy depends only on the state of the system, not on how it got there.

87.One calorie is equal to: (SZABMU MDCAT 2023)

  1. 4.18 KJ
  2. 4.18 J
  3. 0.418 KJ mole-1
  4. 0.418 KJ
Show answer

Correct answer: (b) 4.18 J

One calorie is $4.18\,\mathrm{J}$.

88.What is the reason of energy changes in chemical reactions? (UHS MDCAT 2023)

  1. Bond formation
  2. Bond breakage
  3. Bond formation and breakage
  4. Ionic bonds
Show answer

Correct answer: (c) Bond formation and breakage

Breaking bonds absorbs energy and forming them releases it; the difference is the heat of reaction.

89.What is the unit of heat capacity? (UHS MDCAT 2023)

  1. JK-1
  2. kJmol-1
  3. kJ/K
  4. kJ.mol
Show answer

Correct answer: (a) JK-1

Heat capacity is heat per unit rise in temperature, so its unit is the joule per kelvin.

90.Q.88 Born-Haber cycle is used to determine the Lattice energy of ionic compounds. It is the application of (UHS MDCAT 2023)

  1. Henry's law
  2. Le - Chatleir's Principle
  3. Hess's law
  4. Common ion effect
Show answer

Correct answer: (c) Hess's law

The cycle adds enthalpies round a closed path, which is Hess’s law.

91.The thermal energy at constan pressure is called: (SZABMU MDCAT 2023)

  1. Enthalpy
  2. Internal energy
  3. Heat capacity
  4. Work done
Show answer

Correct answer: (a) Enthalpy

Heat exchanged at constant pressure is the enthalpy change.

92.The correct equation for the first law of thermodynamics is: (SZABMU MDCAT 2023)

  1. ∆E = q + w
  2. ∆E = w - q
  3. ∆E = ∆q - p∆v
  4. ∆E = ∆q + p∆v
Show answer

Correct answer: (a) ∆E = q + w

The first law is $\Delta E=q+w$: heat put in and work done on the system.

Electrochemistry

93.Q.90 An electrochemical cell is based upon which reaction? (UHS MDCAT 2023)

  1. Acid-base reaction
  2. Redox reaction
  3. Nuclear reaction
  4. Neutralization reaction
Show answer

Correct answer: (b) Redox reaction

An electrochemical cell draws its emf from a redox reaction split between two electrodes.

94.The branch of science which deals with the conversion of electrical energy to chemical energy and vice versa is called: (SZABMU MDCAT 2023)

  1. Electrochemistry
  2. Thermochemistry
  3. Stereochemistry
  4. Biochemistry
Show answer

Correct answer: (a) Electrochemistry

That is electrochemistry.

95.The oxidation number of a free element is: (MDCAT 2023)

  1. zero
  2. $+1$
  3. $-1$
  4. equal to its group number
Show answer

Correct answer: (a) zero

An uncombined atom has shared its electrons with nothing, so its oxidation number is zero.

96.Q.91 In which of the following, oxygen shows fractional oxidation number? (UHS MDCAT 2023)

  1. OF2
  2. Na2O2
  3. KO2
  4. Cl2O7
Show answer

Correct answer: (c) KO2

In the superoxide ion the charge is shared between two oxygens, so each is at $-\tfrac12$.

97.Q.94 Which statement describes the conversion of magnesium atoms to magnesium ions for ionic bond formation with chlorine? (UHS MDCAT 2023)

  1. The change is reduction, because there has been a gain of electrons
  2. The change is oxidation, because there has been a loss of electrons
  3. The change is reduction, because there has been a loss of electrons
  4. The change is oxidation, because there has been a gain of electrons
Show answer

Correct answer: (b) The change is oxidation, because there has been a loss of electrons

Magnesium gives up two electrons, and loss of electrons is oxidation.

98.Oxidation number of an element in free state is: (SZABMU MDCAT 2023)

  1. Negative
  2. Positive
  3. Zero
  4. ±1
Show answer

Correct answer: (c) Zero

An uncombined element has an oxidation number of zero.

99.During electrolysis, reduction always occurs at the: (NUMS MDCAT 2023)

  1. Anode
  2. Cathode
  3. SHE
  4. Salt bridge
Show answer

Correct answer: (b) Cathode

Reduction is gain of electrons, and the electrons enter the cell at the cathode.

100.0xidation number of free magnesium is? (UHS MDCAT 2023)

  1. 0
  2. +1
  3. +2
  4. +3
Show answer

Correct answer: (a) 0

An uncombined element has an oxidation number of zero.

101.Which statement correctly describes the term Standard Electrode Potential? (SZABMU MDCAT 2023)

  1. It is the electrode potential determined at room temperature and pressure
  2. It is the electrode potential determined under standard conditions using StandardHydrogen Electrode as the other electrode
  3. It is the electrode potential of an element and its solution compared to a standard value
  4. It is the potential which is measured when two half cells are connected together
Show answer

Correct answer: (b) It is the electrode potential determined under standard conditions using StandardHydrogen Electrode as the other electrode

It is measured under standard conditions against the standard hydrogen electrode.

Chemical Bonding

102.Valance shell electron pair repulsion theory explains: (NUMS MDCAT 2023)

  1. Bond Energy
  2. Bond Length
  3. Shapes and Bond Energy
  4. Shapes
Show answer

Correct answer: (d) Shapes

VSEPR predicts the shape of a molecule from the repulsion of its electron pairs.

103.Carbon atoms in ethane are hybridized: (SZABMU MDCAT 2023)

  1. Sp3
  2. Sp2
  3. Sp
  4. Sp3d
Show answer

Correct answer: (a) Sp3

Each carbon of ethane has four sigma bonds, so it is sp3.

104.In alkanes, each Carbon has hybridization: (SZABMU MDCAT 2023)

  1. Sp3
  2. Sp
  3. Sp2
  4. dsp
Show answer

Correct answer: (a) Sp3

Every carbon of an alkane makes four sigma bonds, so all are sp3.

105.Which of the following has sp3 hybridization? (NUMS MDCAT 2023)

  1. BF3
  2. C2H4
  3. BeCl2
  4. CH4
Show answer

Correct answer: (d) CH4

Carbon in methane has four sigma bonds and no lone pair, so it is sp3.

106.Q.96 Why dimer of Aluminum chloride is formed (UHS MDCAT 2023)

  1. Aluminum is electron rich
  2. Aluminum is having lone pair of electron
  3. Aluminum donates lone pair to form bridge
  4. Aluminum forms coordinate bonds with chlorine to complete its octet
Show answer

Correct answer: (d) Aluminum forms coordinate bonds with chlorine to complete its octet

Aluminium is two electrons short of an octet, so a chlorine of the other molecule donates a pair as a bridge.

107.Q.95 AB4 Type with no Lone Pairs geometry enables to form which shape of molecule? (UHS MDCAT 2023)

  1. Trigonal
  2. Regular tetrahedron
  3. Regular octahedron
  4. Regular pyramidal
Show answer

Correct answer: (b) Regular tetrahedron

Four bond pairs and no lone pair repel into a regular tetrahedron.

108.What is the reason for energy changes in chemical reactions? (MDCAT 2023)

  1. ionic bonds
  2. bond breakage only
  3. bond formation and breakage
  4. hydrogen bonding
Show answer

Correct answer: (c) bond formation and breakage

Breaking bonds absorbs energy and forming them releases it, and the balance of the two is the enthalpy change.

109.The bond energy of hydrogen in the $\mathrm{H_2}$ molecule is: (MDCAT 2023)

  1. $242\ \mathrm{kJ\,mol^{-1}}$
  2. $431\ \mathrm{kJ\,mol^{-1}}$
  3. $436\ \mathrm{kJ\,mol^{-1}}$
  4. $346\ \mathrm{kJ\,mol^{-1}}$
Show answer

Correct answer: (c) $436\ \mathrm{kJ\,mol^{-1}}$

It takes $436\ \mathrm{kJ\,mol^{-1}}$ to break the H-H bond.

110.The factor which is not affecting bond length is: (NUMS MDCAT 2023)

  1. Pressure of multiple bonds
  2. Nature of hybridization present
  3. Difference in electronegativity between the two bonded atoms
  4. Ionization energies of the two bonded atoms
Show answer

Correct answer: (d) Ionization energies of the two bonded atoms

Bond length turns on the size of the atoms, the bond order and the hybridization, not on ionization energy.

111.The bond energy of hydrogen in H2 molecule is: (UHS MDCAT 2023)

  1. 242 KJ/mol
  2. 431 KJ/mol
  3. 436 KJ/mol
  4. 346 KJ/mol
Show answer

Correct answer: (c) 436 KJ/mol

The bond in hydrogen takes $436\,\mathrm{kJ\,mol^{-1}}$ to break.

s- and p-Block Elements

112.Which of the following has the highest atomic radius in its period? (MDCAT 2023)

  1. alkaline earth metals
  2. alkali metals
  3. chalcogens
  4. halogens
Show answer

Correct answer: (b) alkali metals

The radius falls across a period, so the group I element at the start of each period is the largest.

113.Why does fluorine have less electron affinity as compared to bromine? (MDCAT 2023)

  1. its electronegativity
  2. its small size and dense electronic cloud
  3. seven electrons in its outermost shell
  4. its higher ionization energy
Show answer

Correct answer: (b) its small size and dense electronic cloud

The incoming electron is crowded into a very small $2p$ shell, and the repulsion there offsets the attraction of the nucleus.

114.Q.92 Which of the following element has smaller size? (UHS MDCAT 2023)

  1. Na
  2. K
  3. Al
  4. Li
Show answer

Correct answer: (c) Al

Aluminium is furthest to the right in its period of the four, so its atom is the smallest.

115.Q.93 Among LiCl, BeCl2, NaCl, CsCl, the compounds with the greatest and the least ionic character respectively are: (UHS MDCAT 2023)

  1. LiCl and CsCl
  2. NaCl and LiCl
  3. CsCl and NaCl
  4. CsCl and BeCl2
Show answer

Correct answer: (d) CsCl and BeCl2

Ionic character grows with the size of the cation and falls with its charge, so caesium chloride is most ionic and beryllium chloride least.

116.Which of the following has greatest difference of electronegativity? (SZABMU MDCAT 2023)

  1. HF
  2. HCl
  3. HBr
  4. HI
Show answer

Correct answer: (a) HF

Fluorine is the most electronegative element, so its bond to hydrogen is the most polar.

117.Ionization energy decreases down the group because: (SZABMU MDCAT 2023)

  1. Shielding remains constant
  2. Atomic radius remains constant
  3. Proton number increases
  4. Atomic radius increases
Show answer

Correct answer: (d) Atomic radius increases

The outer electron is further from the nucleus and better screened, so it is easier to remove.

118.Which of the following property decreases in Group 2 as we go down the group? (SZABMU MDCAT 2023)

  1. Shielding
  2. Atomic radius
  3. Proton number
  4. Ionization energy
Show answer

Correct answer: (d) Ionization energy

The atom grows and its outer electron is easier to pull off, so ionization energy falls.

119.The reason of highest electronegativity value of Fluorine is: (NUMS MDCAT 2023)

  1. Complete outermost shell
  2. Ability to form negative ion
  3. Existence as diatomic molecule
  4. Smaller size and higher nuclear charge in the respective period
Show answer

Correct answer: (d) Smaller size and higher nuclear charge in the respective period

Fluorine is the smallest atom of its period with a high nuclear charge, so it pulls hardest on a shared pair.

120.The electronic configurations of some elements are given below. Recognize the element that belongs to group IIIA. (MDCAT 2023)

  1. $1s^2\,2s^2\,2p^1$
  2. $1s^2\,2s^2\,2p^4$
  3. $1s^2\,2s^2\,2p^5$
  4. $1s^2\,2s^2\,2p^2$
Show answer

Correct answer: (a) $1s^2\,2s^2\,2p^1$

Three electrons in the valence shell put the element in group IIIA; this is boron.

121.Q.97 Which group of the periodic table contain non-metals, metalloids and metals. (UHS MDCAT 2023)

  1. I B
  2. VII A
  3. IV A
  4. VI A
Show answer

Correct answer: (c) IV A

Group IV runs from carbon, a non-metal, through silicon and germanium to tin and lead, which are metals.

122.Which of the following is semiconductor? (SZABMU MDCAT 2023)

  1. Al
  2. Si
  3. P
  4. Mg
Show answer

Correct answer: (b) Si

Silicon lies on the metalloid boundary of group IV and is the classic semiconductor.

123.Select the metal which is extracted from bauxite? (UHS MDCAT 2023)

  1. Al
  2. Ca
  3. Mg
  4. Cu
Show answer

Correct answer: (a) Al

Bauxite is hydrated aluminium oxide, from which aluminium is won by electrolysis.

124.The alkali metals react with chlorine gas to form white metal chloride salts. The metal chloride salt formed is: (MDCAT 2023)

  1. insoluble in water
  2. soluble in water to give a neutral solution
  3. soluble in water to give an acidic solution
  4. soluble in water to give an alkaline solution
Show answer

Correct answer: (b) soluble in water to give a neutral solution

Both ions come from a strong base and a strong acid, so neither hydrolyses and the solution is neutral.

125.Which of the following alkali metal can form normal oxides as well as peroxides? (SZABMU MDCAT 2023)

  1. Na
  2. K
  3. Li
  4. Cs
Show answer

Correct answer: (a) Na

Sodium gives both the oxide and the peroxide; lithium gives only the oxide.

126.All alkali metals react with chlorine gas to form white metal chlorides salt. The metal chlorides salt formed is: (UHS MDCAT 2023)

  1. Insoluble
  2. Soluble in water to give neutral solution of ph 7
  3. Soluble in water to give acidic solution of ph 1
  4. Soluble in water to give alkaline solution of ph 14
Show answer

Correct answer: (b) Soluble in water to give neutral solution of ph 7

An alkali metal chloride is the salt of a strong acid and a strong base, so its solution is neutral.

127.Which one of these oxides is amphoteric in nature? (MDCAT 2023)

  1. lithium oxide
  2. beryllium oxide
  3. calcium oxide
  4. potassium oxide
Show answer

Correct answer: (b) beryllium oxide

Beryllium oxide reacts both with acids and with alkalis; the other three are basic.

128.Q.98 Which of the following sulfate compound is insoluble in water ? (UHS MDCAT 2023)

  1. BeSO4
  2. BaSO4
  3. MgSO4
  4. CaSO4
Show answer

Correct answer: (b) BaSO4

Solubility of the group II sulphates falls down the group, and barium sulphate is insoluble.

129.Which one of them is amphoteric in nature? (UHS MDCAT 2023)

  1. Lithium oxide
  2. Beryllium oxide
  3. Calcium oxide
  4. Potassium oxide
Show answer

Correct answer: (b) Beryllium oxide

Beryllium oxide dissolves in both acid and alkali, so it is amphoteric.

Transition Elements

130.Which of the following electronic configurations is correct for $_{24}\mathrm{Cr}$? (MDCAT 2023)

  1. $[\mathrm{Ar}]3d^54s^1$
  2. $[\mathrm{Ar}]3d^44s^2$
  3. $[\mathrm{Ar}]3d^64s^0$
  4. $[\mathrm{Ar}]3d^34s^2$
Show answer

Correct answer: (a) $[\mathrm{Ar}]3d^54s^1$

One electron moves from $4s$ to $3d$ to give the more stable half-filled $d$ set.

131.Which of the following transition metals shows a $3d^5$ configuration in its $+2$ oxidation state? (MDCAT 2023)

  1. $\mathrm{Cu^{2+}}$
  2. $\mathrm{Fe^{2+}}$
  3. $\mathrm{Mn^{2+}}$
  4. $\mathrm{Zn^{2+}}$
Show answer

Correct answer: (c) $\mathrm{Mn^{2+}}$

Manganese is $[\mathrm{Ar}]3d^54s^2$, so losing the two $4s$ electrons leaves $3d^5$.

132.Q.99 Which of the following complex show a tetrahedral geometry? (UHS MDCAT 2023)

  1. [Fe(CO)5]
  2. [Cu(CN)4]-2
  3. [Au(Cl)4]-
  4. [Pt(NH3)4]+2
Show answer

Correct answer: (b) [Cu(CN)4]-2

Four ligands round a copper(I) centre with no d-orbital preference give a tetrahedron.

133.In which pair one has all Unpaired d orbitals while other have all paired d orbitals ? (UHS MDCAT 2023)

  1. Cu and Zn
  2. Cr and Fe
  3. Cr and Zn
  4. Mn and Co
Show answer

Correct answer: (c) Cr and Zn

Chromium is $3d^5$, all five unpaired; zinc is $3d^{10}$, all paired.

134.The transition element which doesn’t show variable valency: (SZABMU MDCAT 2023)

  1. Cu
  2. Sc
  3. Zn
  4. Cr
Show answer

Correct answer: (c) Zn

Zinc has a full d subshell, so it can only give up its two 4s electrons.

135.The binding energy of transition metals increases upto group: (SZABMU MDCAT 2023)

  1. II B
  2. IV B
  3. III B
  4. VI B
Show answer

Correct answer: (d) VI B

More unpaired d electrons mean stronger metallic bonding, and that peaks around group VI B.

136.Which of the following transition metal show 3d5 configuration in its +2-oxidation state? (UHS MDCAT 2023)

  1. Cu+2
  2. Fe+2
  3. Mn+2
  4. Zn+2
Show answer

Correct answer: (c) Mn+2

Manganese(II) has lost its two 4s electrons, leaving a half filled $3d^5$ subshell.

Fundamental Principles of Organic Chemistry

137.What is the molecular formula of the pyridine molecule? (MDCAT 2023)

  1. $\mathrm{C_6H_5N}$
  2. $\mathrm{C_5H_5N}$
  3. $\mathrm{C_4H_4N}$
  4. $\mathrm{C_6H_6N}$
Show answer

Correct answer: (b) $\mathrm{C_5H_5N}$

Pyridine is benzene with one CH replaced by N, so it is $\mathrm{C_5H_5N}$.

138.Homo-cyclic organic compounds are sub divided into two groups namely: (SZABMU MDCAT 2023)

  1. Alicyclic and Aromatic
  2. Open chain and branched chain
  3. Aromatic and non-aromatic
  4. Anti-aromatic
Show answer

Correct answer: (a) Alicyclic and Aromatic

A homocyclic ring of carbon alone is either alicyclic or aromatic.

139.Generic formula of cycloalkane is: (NUMS MDCAT 2023)

  1. CnH2n+2
  2. CnH2n
  3. CnH2n−1
  4. CnCH2n−2
Show answer

Correct answer: (b) CnH2n

A ring costs two hydrogens, so a cycloalkane is $\mathrm{C_nH_{2n}}$.

140.What is the molecular formula of pyridine molecule? (UHS MDCAT 2023)

  1. C6H5N
  2. C5H5N
  3. C5H5NH
  4. C6H6N
Show answer

Correct answer: (b) C5H5N

Pyridine is benzene with one carbon replaced by nitrogen, so its formula is $\mathrm{C_5H_5N}$.

141.In which of the following functional groups, the carbon atom is sp hybridized? (UHS MDCAT 2023)

  1. -CHO
  2. -COOH
  3. -CN
  4. -COOR
Show answer

Correct answer: (c) -CN

The carbon of a nitrile is triply bonded to nitrogen, so it is sp hybridized.

142.The compounds containing R-SH functional group are known as: (UHS MDCAT 2023)

  1. Alcohols
  2. Thio-alcohols
  3. Thio-ether
  4. Nitrile
Show answer

Correct answer: (b) Thio-alcohols

Replacing the oxygen of an alcohol with sulphur gives a thio-alcohol, or thiol.

143.Which of the functional group are present in ethyl acetate? (UHS MDCAT 2023)

  1. Aldehyde group
  2. Carboxyl group
  3. Ester group
  4. Ether group
Show answer

Correct answer: (c) Ester group

Ethyl acetate is the ester of acetic acid and ethanol.

144.What are vinyl alcohol and acetaldehyde? (MDCAT 2023)

  1. position isomers
  2. chain isomers
  3. metamers
  4. tautomers
Show answer

Correct answer: (d) tautomers

They differ by the place of a hydrogen and a double bond and interconvert, which makes them tautomers.

145.The type of isomerism arising due to shifting of proton fron one atom to another in the same molecule is: (SZABMU MDCAT 2023)

  1. Chain isomerism
  2. Metamerism
  3. Tautomerism
  4. Postion isomerism
Show answer

Correct answer: (c) Tautomerism

A proton shifting within the molecule between two forms in equilibrium is tautomerism.

Chemistry of Hydrocarbons

146.Consider the chlorination of methane, the attack of chlorine free radical on methane form methyl free radical occurs in ? (UHS MDCAT 2023)

  1. Initiation step
  2. Propagation step
  3. Termination step
  4. Last step
Show answer

Correct answer: (b) Propagation step

A radical is used and another is made, which is the mark of a propagation step.

147.The addition reaction of 2-butene with HBr produces: (MDCAT 2023)

  1. 1-bromobutane
  2. 2-bromobutane
  3. 3-bromobutane
  4. 2,3-dibromobutane
Show answer

Correct answer: (b) 2-bromobutane

Either carbon of the double bond is equivalent here, so the bromine ends up on carbon 2.

148.Alkylbenzene is formed when benzene is treated with an alkyl halide in the presence of anhydrous aluminium chloride. Identify the type of reaction. (MDCAT 2023)

  1. halogenation
  2. Friedel-Crafts acylation
  3. Friedel-Crafts alkylation
  4. sulphonation
Show answer

Correct answer: (c) Friedel-Crafts alkylation

The Lewis acid makes a carbocation from the halide, which substitutes into the ring: Friedel-Crafts alkylation.

149.Alkylbenzene is formed when benzene is treated with an alkyl halide in the presence of anhydrous aluminum chloride. Identify the type of reaction. (UHS MDCAT 2023)

  1. Halogenation
  2. Friedel-Crafts acylation reaction
  3. Friedel-Crafts alkylation reaction
  4. Sulphonation
Show answer

Correct answer: (c) Friedel-Crafts alkylation reaction

An alkyl group is put on the ring with an alkyl halide and aluminium chloride, which is Friedel-Crafts alkylation.

150.Acetophenone can be formed by which of the following reaction of benzene? (NUMS MDCAT 2023)

  1. Alkylation
  2. Acylation
  3. Halogenation
  4. Nitration
Show answer

Correct answer: (b) Acylation

Friedel-Crafts acylation with acetyl chloride puts the acetyl group on the ring.

151.Identify the method which is used to prepare alkynes. (MDCAT 2023)

  1. dehalogenation of vicinal dihalides in the presence of methanol
  2. dehydration of alcohols in the presence of $\mathrm{Al_2O_3}$ at 340-450$^\circ$C
  3. dehydrohalogenation of vicinal dihalides in the presence of a strong base
  4. electrolysis of carboxylic acid salts
Show answer

Correct answer: (c) dehydrohalogenation of vicinal dihalides in the presence of a strong base

A strong base removes two molecules of hydrogen halide from the vicinal dihalide and leaves a triple bond.

152.The cracking method used to obtain better quality gasoline is: (NUMS MDCAT 2023)

  1. Thermal
  2. Catalytic
  3. Steam
  4. Radiations
Show answer

Correct answer: (b) Catalytic

Catalytic cracking gives branched and aromatic products, which have the higher octane number.

153.Which of the following reagents can be used to distinguish between 1-pentyne and 2-pentyne? (MDCAT 2023)

  1. $\mathrm{AgNO_3+NH_4OH}$
  2. dilute alkaline $\mathrm{KMnO_4}$
  3. $\mathrm{Br_2/CCl_4}$
  4. $\mathrm{K_2Cr_2O_7+H_2SO_4}$
Show answer

Correct answer: (a) $\mathrm{AgNO_3+NH_4OH}$

Only the terminal alkyne has an acidic hydrogen, so only 1-pentyne gives a silver acetylide precipitate.

154.Which of the following compound is more acidic? (UHS MDCAT 2023)

  1. Alkane
  2. Alkene
  3. Alkyne
  4. Cycloalkane
Show answer

Correct answer: (c) Alkyne

The sp carbon of a terminal alkyne holds its electrons closely, so its hydrogen leaves most readily.

155.Propanone can be prepared from propyne by: (MDCAT 2023)

  1. passing a mixture of propyne and steam over a catalyst of magnesium at $420^\circ$C
  2. passing a mixture of propyne and ethanol over a catalyst of zinc chromate
  3. boiling propyne with water in the presence of $\mathrm{HgSO_4}$ and $\mathrm{H_2SO_4}$
  4. treating propyne with iodine and NaOH
Show answer

Correct answer: (c) boiling propyne with water in the presence of $\mathrm{HgSO_4}$ and $\mathrm{H_2SO_4}$

Acid-catalysed hydration of the triple bond follows Markovnikov's rule and gives the ketone.

156.Three alternate single and double bonds in benzene are called? (UHS MDCAT 2023)

  1. Conjugate bonds
  2. Coordinate covalent bonds
  3. Fixed bonds
  4. Ionic bonds
Show answer

Correct answer: (a) Conjugate bonds

Alternating single and double bonds make a conjugated system, and the electrons of it are delocalized.

157.Under suitable conditions, alkanes cannot undergo which of the following reactions? (MDCAT 2023)

  1. substitution
  2. combustion
  3. hydrogenation
  4. addition
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Correct answer: (d) addition

An alkane is already saturated, so it has no place to add anything; it reacts by substitution.

158.The correct order of reactivity of hydrocarbons is: (SZABMU MDCAT 2023)

  1. Alkanes ˃ Alkynes ˃ Alkenes
  2. Alkenes ˃ Alkanes ˃ Alkynes
  3. Alkynes ˃ Alkenes ˃ Alkanes
  4. Alkenes ˃ Alkynes ˃ Alkanes
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Correct answer: (d) Alkenes ˃ Alkynes ˃ Alkanes

The loose pi electrons of an alkene are the most available, and the saturated alkane has none.

159.Under suitable conditions alkanes cannot undergo ___________ reactions? (UHS MDCAT 2023)

  1. Substitution
  2. Combustion
  3. Hydrogenation
  4. Addition
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Correct answer: (d) Addition

An alkane is saturated, so nothing can add to it; it can only substitute or burn.

160.Which of the following is not oxidized by any oxidizing agent? (SZABMU MDCAT 2023)

  1. Benzene
  2. Toulene
  3. Ethylbenzene
  4. Xylene
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Correct answer: (a) Benzene

Benzene resists oxidation; the side chain of an alkylbenzene is oxidized instead.

Alkyl Halides

161.Freon is commonly known as ? (UHS MDCAT 2023)

  1. Refrigerant
  2. A solvent
  3. Insecticides
  4. A fire extinguisher
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Correct answer: (a) Refrigerant

The freons are chlorofluorocarbons, used as refrigerants for their low boiling points and inertness.

162.Alkyl halides are also known as Halogen derivatives of: (SZABMU MDCAT 2023)

  1. Alkanes
  2. Alkenes
  3. Alkynes
  4. Alcohols
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Correct answer: (a) Alkanes

An alkyl halide is an alkane with a halogen in place of a hydrogen.

163.Reactivity of order of halogen acid is: (SZABMU MDCAT 2023)

  1. HF ˃ HCl ˃ HBr ˃ HI
  2. HBr ˃ HCl ˃ HI
  3. HCl ˃ HBr ˃ HI ˃ HF
  4. HI ˃ HBr ˃ HCl ˃ HF
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Correct answer: (d) HI ˃ HBr ˃ HCl ˃ HF

The weakest bond breaks first, and the bond to hydrogen is weakest in hydrogen iodide.

164.Grignard reagent is formed when alkyl halide reacts in the presence of halogen with: (SZABMU MDCAT 2023)

  1. Calcium
  2. Potassium
  3. Sodium
  4. Magnesium
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Correct answer: (d) Magnesium

Magnesium in dry ether inserts itself into the carbon halogen bond to give the Grignard reagent.

165.In SN1 reactions the correct order of reactivity of alkyl halide is? (UHS MDCAT 2023)

  1. Primary>secondary>tertiary
  2. Tertiary>secondary>primary
  3. Secondary>primary>tertiary
  4. Primary>tertiary >secondary
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Correct answer: (b) Tertiary>secondary>primary

The first step makes a carbocation, and that is most stable for the tertiary halide.

166.In $\mathrm{S_N1}$ reactions the correct order of reactivity of alkyl halides is: (MDCAT 2023)

  1. primary $>$ secondary $>$ tertiary
  2. tertiary $>$ secondary $>$ primary
  3. secondary $>$ tertiary $>$ primary
  4. tertiary $>$ primary $>$ secondary
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Correct answer: (b) tertiary $>$ secondary $>$ primary

The step that decides the rate is the formation of the carbocation, and a tertiary carbocation is the most stable.

167.When 2-bromopropane reacts with Sodium ethoxide, the major product is/are? (UHS MDCAT 2023)

  1. Propane
  2. Propene
  3. Ethyl isopropyl ether
  4. All are formed
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Correct answer: (b) Propene

Ethoxide is a strong base, so elimination wins over substitution and propene is left.

Alcohols and Phenols

168.Ethanol gives which of the following products in the presence of $\mathrm{H_2SO_4}$ at $140^\circ$C? (MDCAT 2023)

  1. ether
  2. alkene
  3. ethyl acetate
  4. aldehyde
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Correct answer: (a) ether

At $140^\circ$C two molecules of alcohol condense to diethyl ether; at $180^\circ$C the product is ethene instead.

169.The complete oxidation of a primary alcohol gives which of the following? (MDCAT 2023)

  1. aldehyde
  2. alkene
  3. carboxylic acid
  4. ketone
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Correct answer: (c) carboxylic acid

The aldehyde is only the halfway stage; oxidation carried to completion gives the acid.

170.The order of reactivity of alcohol when C-O bond breaks is: (NUMS MDCAT 2023)

  1. Tertiary alcohol > secondary alcohol > Primary alcohol
  2. Secondary alcohol > primary alcohol > tertiary alcohol
  3. Primary alcohol > secondary alcohol > tertiary alcohol
  4. Tertiary alcohol > primary alcohol > secondary alcohol
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Correct answer: (a) Tertiary alcohol > secondary alcohol > Primary alcohol

The carbocation left when the bond breaks is most stable for the tertiary alcohol.

171.Complete oxidation of alcohol gives which of the following? (UHS MDCAT 2023)

  1. Aldehyde
  2. Alkane
  3. Carboxylic acid
  4. Ketone
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Correct answer: (c) Carboxylic acid

A primary alcohol is oxidized first to the aldehyde and then on to the acid.

172.If phenol is treated with 3 moles of concentrated $\mathrm{HNO_3}$ in the presence of $\mathrm{H_2SO_4}$, what will be the product? (MDCAT 2023)

  1. o-nitrophenol
  2. p-nitrophenol
  3. o-nitrophenol and p-nitrophenol
  4. picric acid
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Correct answer: (d) picric acid

Three nitro groups enter the activated ring at positions 2, 4 and 6, giving 2,4,6-trinitrophenol, which is picric acid.

173.Phenols are very reactive towards: (SZABMU MDCAT 2023)

  1. Oxidizing agent
  2. Reducing agent
  3. Dehydrating agent
  4. Hygroscopic agent
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Correct answer: (a) Oxidizing agent

The ring is electron rich, so phenol is oxidized easily, to quinone.

174.If phenol is treated with 3 moles of conc. HNO3 in the presence of H2SO4 what will be the product? (UHS MDCAT 2023)

  1. o-nitro phenol
  2. p-nitro phenol
  3. o-nitro phenol and p-nitro phenol
  4. picric acid
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Correct answer: (d) picric acid

Three nitro groups go on to the ring and the product is 2,4,6-trinitrophenol, picric acid.

175.Both alcohols and phenols contain: (SZABMU MDCAT 2023)

  1. – OH group
  2. – COOH group
  3. – CH2 group
  4. – CHO group
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Correct answer: (a) – OH group

Both carry the hydroxyl group; in a phenol it is attached to a benzene ring.

176.Which of the following reactions differentiates alcohol from phenol? (NUMS MDCAT 2023)

  1. Lucas test
  2. Halogenations
  3. Nitration
  4. Iodoform test
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Correct answer: (a) Lucas test

Lucas reagent reacts with alcohols; phenol does not give a halide at all.

Aldehydes and Ketones

177.Q.115 Which of the following is the correct name of CH3CH2CH2COCH2CHO? (UHS MDCAT 2023)

  1. 3-oxo hexanal
  2. 3-one hexanal
  3. 3-oxo hexanol
  4. 3- keto hexanol
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Correct answer: (a) 3-oxo hexanal

The aldehyde is the senior group, so the chain is hexanal with the ketone named as a 3-oxo substituent.

178.Q.119 If carboxylic acid and ketone groups C=O are present in a chain then final name will be given as (UHS MDCAT 2023)

  1. oxo, oic acid
  2. one, oic acid
  3. Both 1 and 2
  4. None of these
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Correct answer: (a) oxo, oic acid

The acid takes the suffix and the ketone is named as an oxo substituent.

179.What is the ILIPAC name of diisopropyi ketone? (UHS MDCAT 2023)

  1. 1,3-Dilsopropylpropan-2-one
  2. 2,4-Dimethylpentan-3-one
  3. 2,4-Dimethylpentan-2-one
  4. 1,3-Dimethylpropan-2-one
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Correct answer: (b) 2,4-Dimethylpentan-3-one

The longest chain is pentane with the carbonyl at C3 and a methyl on C2 and C4.

180.When Phenol reacts with formaldehyde, which of the following product is produced? (UHS MDCAT 2023)

  1. Adduct
  2. Hydronium ion
  3. Oxonium ion
  4. Phenoxide ion
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Correct answer: (a) Adduct

The ring attacks the carbonyl carbon and an addition product, the adduct, is formed first.

181.Which of the following is also called silver mirror test? (UHS MDCAT 2023)

  1. Benedict's solution test
  2. Fehling's solution test
  3. Iodoform test
  4. Tollen's reagent test
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Correct answer: (d) Tollen's reagent test

Tollens’ reagent leaves a mirror of silver on the wall of the tube.

182.Catalytic reduction of Aldehyde & Ketone forms: (SZABMU MDCAT 2023)

  1. Alcohol
  2. Carboxylic acid
  3. Alkane
  4. Aldehyde
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Correct answer: (a) Alcohol

Hydrogen over a metal catalyst takes the carbonyl group down to an alcohol.

183.When Aldehyde reacts with 50% NaOH, this reaction is called as: (SZABMU MDCAT 2023)

  1. 2, 4 – DNPH reaction
  2. Aldol condensation reaction
  3. Clemmensen reaction
  4. Cannizarros’s reaction
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Correct answer: (d) Cannizarros’s reaction

An aldehyde with no alpha hydrogen disproportionates in strong alkali, which is the Cannizzaro reaction.

184.The appearance of a silver mirror in Toliens test indicates the presence of which of the following? (UHS MDCAT 2023)

  1. A ketone
  2. An aldehyde
  3. An acid
  4. An alcohol
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Correct answer: (b) An aldehyde

Only an aldehyde reduces Tollens’ reagent and leaves the silver mirror.

Carboxylic Acids

185.If both a carboxylic acid group and a ketone group are present in a chain, then the final name will be given as: (MDCAT 2023)

  1. oxo...oic acid
  2. one...oic acid
  3. al...oic acid
  4. none of these
Show answer

Correct answer: (a) oxo...oic acid

The acid takes the suffix, so the ketone is named as an oxo prefix.

186.Hydrolysis of Nitriles produces: (NUMS MDCAT 2023)

  1. Carboxylic acid
  2. Aldehydes
  3. Ketones
  4. Esters
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Correct answer: (a) Carboxylic acid

A nitrile hydrolyses to the carboxylic acid with one more carbon than the alkyl group.

187.Acetic acid is a weaker acid than sulphuric acid because of which of the following reasons? (MDCAT 2023)

  1. it decomposes on increasing temperature
  2. it has less degree of ionisation
  3. it has a $-\mathrm{COOH}$ group
  4. it has a greater inductive effect
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Correct answer: (b) it has less degree of ionisation

Only a small fraction of its molecules ionize in water, so the concentration of $\mathrm{H^+}$ it gives is far lower.

188.Which among the following have least pH? (UHS MDCAT 2023)

  1. CH3CH2COOH
  2. CH2ClCH2COOH
  3. CH3CHCl2 COOH
  4. CH3CH2CH2COOH
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Correct answer: (c) CH3CHCl2 COOH

Two chlorines pull the hardest on the carboxyl group, so that acid is the strongest and its pH the lowest.

189.Select the correct order of relative acidic strength of phenol, alcohol, water, and carboxylic acid: (SZABMU MDCAT 2023)

  1. Carboxylic acid ˃ water ˃ phenol ˃ alcohol
  2. Carboxylic acid ˃ phenol ˃ water ˃ alcohol
  3. Carboxylic acid ˃ alcohol ˃ phenol ˃ water
  4. Carboxylic acid ˃ water ˃ alcohol ˃ phenol
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Correct answer: (b) Carboxylic acid ˃ phenol ˃ water ˃ alcohol

The carboxylate ion is best stabilized, then the phenoxide, and an alkoxide least of all.

190.Acetic acid is weak acid than sulphuric acid because of which of the following reasons? (UHS MDCAT 2023)

  1. It decomposes on increasing temperature
  2. It has less degree of ionisation
  3. It has -COOH group
  4. It has more inductive effect
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Correct answer: (b) It has less degree of ionisation

Acetic acid is only slightly ionized in water, while sulphuric acid is ionized almost completely.

191.Acetic acid is mixed with thionyl chloride. Which product is obtained? (MDCAT 2023)

  1. $\mathrm{CH_3COCl+SO_2+HCl}$
  2. $\mathrm{CH_3Cl+CH_3COCl}$
  3. $\mathrm{CH_3COOH+SO_2}$
  4. $\mathrm{CH_3CHO+HCl}$
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Correct answer: (a) $\mathrm{CH_3COCl+SO_2+HCl}$

Thionyl chloride replaces the $-\mathrm{OH}$ of the acid by chlorine, and the by-products are gases.

192.Carboxylic acid reacts with Alcohol to form: (SZABMU MDCAT 2023)

  1. Ester
  2. Aldehyde
  3. Ketone
  4. Alkyl Halide
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Correct answer: (a) Ester

An acid and an alcohol give an ester and water.

193.Which of the following reacts with Carboxylic Acid to form Ester? (NUMS MDCAT 2023)

  1. Aldehyde
  2. Alkyl Halide
  3. Ketones
  4. Alcohol
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Correct answer: (d) Alcohol

An acid and an alcohol give an ester and water.

194.Mr. Khan mix acetic acid with thionyl chloride. Which product is obtained? (UHS MDCAT 2023)

  1. CH3COCI + SO2 + HCl
  2. CH3CI + CH3COCI
  3. CH3COOCH3 + SO2
  4. CH3CI +SO2+HCI
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Correct answer: (a) CH3COCI + SO2 + HCl

Thionyl chloride replaces the hydroxyl group with chlorine and leaves gaseous by-products.

Macromolecules

195.After digestion and before absorption, the products of proteins are: (MDCAT 2023)

  1. amino acids and small polypeptides
  2. only amino acids
  3. only small polypeptides
  4. polysaccharides
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Correct answer: (a) amino acids and small polypeptides

Proteases cut proteins down to amino acids and short peptides, and both are taken up by the intestinal wall.

196.Inhibitors stop an enzyme from working by: (MDCAT 2023)

  1. changing the shape of the enzyme
  2. merging with the substrate instead
  3. blocking the active site of the enzyme
  4. combining with the product of the reaction
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Correct answer: (c) blocking the active site of the enzyme

A competitive inhibitor occupies the active site, so the substrate cannot bind there.

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