MDCAT 2025 Chemistry

MDCAT 2025 Chemistry Past Paper MCQs with Answers

162 Chemistry MCQs that appeared in MDCAT 2025, 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.NaOH + H2SO4 → Na2SO4 + H2O. When 40g of NaOH reacts with 49g of H2SO4, the number of water molecules produced are: (NUMS MDCAT 2025)

  1. 6.02 × 1023
  2. 6.02 × 1024
  3. 1.2044 × 1023
  4. 1.204 × 1024
Show answer

Correct answer: (a) 6.02 × 1023

One mole of the acid and two of the alkali would be needed; the half mole of acid present gives one mole of water.

2.The mass of hydrogen gas needed to produce 51 g ammonia: (SIBA MDCAT 2025)

  1. 6g
  2. 9g
  3. 12g
  4. 15g
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Correct answer: (b) 9g

Fifty-one grams is three moles of ammonia, which needs four and a half moles of hydrogen, that is $9\,\mathrm{g}$.

3.Consider the given balanced chemical equation: 2H2 + O2 -> 2H2O If 4 g of H2 reacts with 32 g of O2 to produce 28 g of H2O, what is the percentage yield of the reaction? (Molar mass of H2 = 2 g/mol, O2 = 32 g/mol and H2O = 18 g/mol) (UHS MDCAT 2025)

  1. 63.6%
  2. 77.8%
  3. 87.5%
  4. 92.5%
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Correct answer: (b) 77.8%

Four grams of hydrogen would give $36\,\mathrm{g}$ of water, so the yield is $28/36$, or $77.8\%$.

4.A chemical reaction has a theoretical yield of 25 g, but only 20 g of product was obtained. What is the percentage yield of the reaction? (UHS MDCAT 2025)

  1. 20%
  2. 25%
  3. 45%
  4. 80%
Show answer

Correct answer: (d) 80%

The yield is the actual over the theoretical, $20/25$, which is $80\%$.

5.If % yield and actual yield is 80 and 20g respectively, what will be theoretical yield? (UHS MDCAT 2025)

  1. 20g
  2. 25g
  3. 30g
  4. 40g
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Correct answer: (b) 25g

The theoretical yield is the actual divided by the fraction, $20/0.8$, which is $25\,\mathrm{g}$.

6.Consider the given reaction: N2 + 3H2 --> 2NH3 If 56 g of N2 reacts with 12 g of H2 and produces 51 g of NH3, what is the theoretical yield (TY) of NH3 and the percentage yield (PY) of the reaction? (Molar mass of N2 = 28 g/mol, H2 = 2 g/mol and NH3 = 17 g/mol) (SIBA MDCAT 2025)

  1. TY = 68 g and PY = 75%
  2. TY = 34 g and PY = 67%
  3. TY = 68 g and PY = 33%
  4. TY = 34 g and PY = 75%
Show answer

Correct answer: (a) TY = 68 g and PY = 75%

Two moles of nitrogen and six of hydrogen are exactly the required ratio, so four moles, $68\,\mathrm{g}$, are possible and $51/68$ is $75\%$.

7.50.0 g Mg is burnt with 32g of oxygen to form MgO, amount of excess reagent left is? (SIBA MDCAT 2025)

  1. 6g Mg
  2. 2g Mg
  3. 8g O2
  4. 16g O2
Show answer

Correct answer: (b) 2g Mg

One mole of oxygen needs two moles, $48\,\mathrm{g}$, of magnesium, so $2\,\mathrm{g}$ of magnesium is left over.

Atomic Structure

8.How much heavier is the H-atom as compared to electron? (NUMS MDCAT 2025)

  1. 1937
  2. 1737
  3. 1837
  4. 1637
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Correct answer: (c) 1837

A hydrogen atom is about 1837 times as massive as an electron.

9.According to Planck's quantum theory, if the frequency of photon is doubled, the value of hf will be: (KMU MDCAT 2025)

  1. Doubled
  2. Increased 3 times
  3. Increased 4 times
  4. Unchanged
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Correct answer: (a) Doubled

The energy of a quantum is $hf$, which is proportional to the frequency.

10.Highest energy for one quantum among radiation is: (SZABMU MDCAT 2025)

  1. microwave
  2. infrared
  3. ultra violet
  4. visible
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Correct answer: (c) ultra violet

Energy is $hf$, and of these four the ultraviolet has the highest frequency.

11.Which set of quantum numbers is not allowed for an electron. (UHS MDCAT 2025)

  1. n=2, l=1, m=0, s=+1/2
  2. n=3, l=0, m=0, s=-1/2
  3. n=2, l=2, m=+1, s=+1/2
  4. n=1, l=0, m=0, s=+1/2
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Correct answer: (c) n=2, l=2, m=+1, s=+1/2

The azimuthal quantum number cannot reach the principal one, so $l=2$ is impossible when $n=2$.

12.Shape of orbital is determined by quantum number: (UHS MDCAT 2025)

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

The azimuthal quantum number $l$ fixes the shape of the orbital; $n$ fixes its size.

13.The number of electrons in a subshell can be calculated by the formula: (NUMS MDCAT 2025)

  1. 2l + 1
  2. 2l + 2
  3. 2(2 + l)
  4. 2(2l + 1)
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Correct answer: (d) 2(2l + 1)

A subshell holds $2(2l+1)$ electrons, so two in s, six in p and ten in d.

14.Number of electron with l=2 in an atom having atomic number 23 is: (SZABMU MDCAT 2025)

  1. 2
  2. 3
  3. 4
  4. 5
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Correct answer: (b) 3

Vanadium is $[\mathrm{Ar}]3d^3 4s^2$, and $l=2$ means the d subshell, which holds three electrons.

15.The maximum probability of finding an electron is at a distance of: (SIBA MDCAT 2025)

  1. 0.53 nm
  2. 0.35 nm
  3. 0.053 nm
  4. 0.0053 nm
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Correct answer: (c) 0.053 nm

The most probable distance of the electron of a hydrogen atom is the Bohr radius, $0.053\,\mathrm{nm}$.

16.Which atom has at least single electron in dumbell shape orbital? (SIBA MDCAT 2025)

  1. H
  2. He
  3. Li
  4. B
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Correct answer: (d) B

The p orbital is dumb-bell shaped, and boron is the first of these with an electron in one.

17.Number of unpaired electrons present in the ground state of Fe3+ are (Atomic number of Fe=26). (UHS MDCAT 2025)

  1. Three
  2. Four
  3. Five
  4. Six
Show answer

Correct answer: (c) Five

Iron(III) is $[\mathrm{Ar}]3d^5$, and five d electrons stay unpaired.

18.Number of unpaired electrons In Boron in ground state is/are: (UHS MDCAT 2025)

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

Boron is $1s^2 2s^2 2p^1$, so the single p electron is the only unpaired one.

19.When 5d orbital is complete, the entering electron goes into: (NUMS MDCAT 2025)

  1. 6s
  2. 6p
  3. 6d
  4. 6f
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Correct answer: (b) 6p

By the $n+l$ rule the 6p subshell is filled after the 5d.

20.Which of the following is expected to be the most paramagnetic? (SIBA MDCAT 2025)

  1. H
  2. Be
  3. B
  4. C
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Correct answer: (d) C

Carbon is $1s^2 2s^2 2p^2$, with two unpaired p electrons, more than any of the others here.

Gases

21.Which of the following is NOT a postulate of kinetic molecular theory of gases? (KMU MDCAT 2025)

  1. Gas molecules undergo elastic collision
  2. Gas molecules are in continuous random motion
  3. Gas molecules do not exert pressure when molecules collide with wall of container
  4. Gas molecules are far away from each other
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Correct answer: (c) Gas molecules do not exert pressure when molecules collide with wall of container

The theory says pressure is precisely the result of those collisions with the walls.

22.Which of the following relationship is correct for kinetic energy of gases? (NUMS MDCAT 2025)

  1. K.E = 2RT/3NA
  2. K.E = 3RT/2NA
  3. K.E = 2mNT/2R
  4. K.E = 2NA/3RT
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Correct answer: (b) K.E = 3RT/2NA

The mean translational energy of one molecule is $\tfrac32RT/N_A$.

23.The fourth state of matter is: (NUMS MDCAT 2025)

  1. Solid
  2. Liquid
  3. Gaseous liquid
  4. Plasma
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Correct answer: (d) Plasma

A gas heated until its atoms ionize becomes plasma, the fourth state of matter.

24.According to the Kinetic molecular theory, the kinetic energy of gas molecules increases when they are (SZABMU MDCAT 2025)

  1. melted from solid to liquid state
  2. mixed with other molecules at lower temperature
  3. frozen into solids
  4. condensed into liquids
Show answer

Correct answer: (a) melted from solid to liquid state

Melting raises the temperature at which the particles move, so their kinetic energy rises.

25.Which statement applies to both ideal and real gases (SZABMU MDCAT 2025)

  1. collision between molecules are elastic
  2. molecules are in constant random motion
  3. molecules attract each other
  4. molecules have zero size
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Correct answer: (b) molecules are in constant random motion

Continuous random motion is common to both; only the ideal gas has point molecules that do not attract.

26.Consider the equation H2 + O2 -> H2O, what volume of hydrogen gas is required to produce 1 mol of water at standard temperature & pressure? (UHS MDCAT 2025)

  1. 11.2 dm3
  2. 22.4 dm3
  3. 10 dm3
  4. 58 dm3
Show answer

Correct answer: (b) 22.4 dm3

One mole of water needs one mole of hydrogen, and a mole of any gas fills $22.4\,\mathrm{dm^3}$ at STP.

27.Select the standard condition for temperature and pressure: (SIBA MDCAT 2025)

  1. 1 atm and 0K
  2. 760 torr and 25°C
  3. 2 bar and 25°C
  4. 14.7 psi and 0°C
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Correct answer: (d) 14.7 psi and 0°C

Standard conditions are one atmosphere, that is $14.7\,\mathrm{psi}$, and $0^{\circ}\mathrm{C}$.

28.Which of the following is true about pressure for an ideal gas at -273°C? (UHS MDCAT 2025)

  1. P=1atm
  2. P=2atm
  3. P=3atm
  4. P=0 atm
Show answer

Correct answer: (d) P=0 atm

At absolute zero the molecular motion stops, so the gas would exert no pressure at all.

29.Absolute zero temperature is equal to: (NUMS MDCAT 2025)

  1. 0°C
  2. -173°C
  3. -273°C
  4. -373°C
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Correct answer: (c) -273°C

Absolute zero is $-273.15^{\circ}\mathrm{C}$, the temperature at which molecular motion would cease.

30.When pressure is 1520 torr then density of oxygen gas will be: (SIBA MDCAT 2025)

  1. 64/RT
  2. 32/RT
  3. 16/RT
  4. 128/RT
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Correct answer: (a) 64/RT

$1520\,\mathrm{torr}$ is two atmospheres, and $d=PM/RT$ gives $2\times32/RT$.

31.Which equation is used to calculate concentration for n mole of an ideal gas? (SIBA MDCAT 2025)

  1. P/RT
  2. PV/RT
  3. CV/RT
  4. PM/RT
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Correct answer: (a) P/RT

Dividing $PV=nRT$ by $V$ gives the concentration $n/V$ as $P/RT$.

32.Keeping temperature constant, if pressure is increased, density of gas will (SZABMU MDCAT 2025)

  1. Increases
  2. decreases
  3. gets doubled
  4. remains same
Show answer

Correct answer: (a) Increases

Density is $PM/RT$, so at fixed temperature it rises with the pressure.

33.Value of R gas constant in J mol-1 K-1 is (UHS MDCAT 2025)

  1. 8.314
  2. 62.4
  3. 0.821
  4. 62400
Show answer

Correct answer: (a) 8.314

In SI units the gas constant is $8.314\,\mathrm{J\,mol^{-1}\,K^{-1}}$.

34.The value of R in atm.dm3.mol-1.K-1 is: (KMU MDCAT 2025)

  1. 0.0821
  2. 0.821
  3. 62.4
  4. 8.314
Show answer

Correct answer: (a) 0.0821

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

35.Real gases show more positive deviation as pressure increases because of (SZABMU MDCAT 2025)

  1. Ionic nature
  2. repulsive forces
  3. attractive forces
  4. non polar nature
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Correct answer: (b) repulsive forces

Squeezed close, the molecules resist further compression, so the volume is larger than the ideal equation predicts.

Liquids

36.Which of the following is responsible for the low boiling point of diethyl ether as compared to water? (NUMS MDCAT 2025)

  1. Weak intermolecular forces
  2. High surface tension
  3. Low vapour pressure
  4. High vapour pressure
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Correct answer: (a) Weak intermolecular forces

Ether molecules attract each other only by weak dipole forces, while water is held by hydrogen bonds.

37.The weakest intermolecular force present in liquid is? (SZABMU MDCAT 2025)

  1. dipole dipole forces
  2. induce dipole force
  3. Instantaneous dipole induced dipole force
  4. hydrogen bonding
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Correct answer: (c) Instantaneous dipole induced dipole force

London forces between instantaneous dipoles are the weakest of the intermolecular attractions.

38.Which one of the following has higher vapour pressure? (UHS MDCAT 2025)

  1. acetone
  2. acetaldehyde
  3. isopentane
  4. Benzene
Show answer

Correct answer: (b) acetaldehyde

Acetaldehyde boils at about $20^{\circ}\mathrm{C}$, the lowest of the four, so its vapour pressure is the highest.

39.Which factor does not affect the rate of evaporation? (NUMS MDCAT 2025)

  1. Amount of liquid
  2. Surface area
  3. Temperature
  4. Inter-molecular forces
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Correct answer: (a) Amount of liquid

Evaporation is a surface process, so its rate depends on the area, the temperature and the forces between molecules, but not on how much liquid there is.

40.Which of the following is least volatile? (SIBA MDCAT 2025)

  1. Glycerol
  2. Water
  3. Acetic acid
  4. Diethyl ether
Show answer

Correct answer: (a) Glycerol

Glycerol has three hydroxyl groups and so the strongest hydrogen bonding of the four.

41.Hydrogen bonding does not exist in: (NUMS MDCAT 2025)

  1. Proteins
  2. Alcohols
  3. Liq HF
  4. SiH4
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Correct answer: (d) SiH4

A hydrogen bond needs hydrogen bound to nitrogen, oxygen or fluorine; silicon is far too weakly electronegative.

Solids

42.Which one shows anisotropic behavior? (UHS MDCAT 2025)

  1. Wood
  2. Gemstone
  3. Coke
  4. Graphite
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Correct answer: (d) Graphite

Graphite conducts and cleaves along its layers but not across them, which is what anisotropy means.

43.Pick the crystalline solids: (UHS MDCAT 2025)

  1. Cement
  2. Ceramics
  3. Concrete
  4. Copper
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Correct answer: (b) Ceramics

Ceramics are crystalline; cement and concrete are amorphous mixtures.

44.Which of the following is not a crystalline solid? (SZABMU MDCAT 2025)

  1. KCl
  2. Fe metal
  3. Glass
  4. rhombic S
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Correct answer: (c) Glass

Glass is a supercooled liquid with no long range order, so it is amorphous.

45.In a unit cell of a crystal lattice the angle β is between faces: (UHS MDCAT 2025)

  1. a and b
  2. b and c
  3. c and a
  4. not specified
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Correct answer: (c) c and a

By convention $\alpha$ lies between b and c, $\beta$ between c and a, and $\gamma$ between a and b.

46.The shape of the crystal lattice depends upon: (NUMS MDCAT 2025)

  1. Size of particles
  2. Nature of particles
  3. Arrangement of particles
  4. Size of unit cell
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Correct answer: (c) Arrangement of particles

The lattice is defined by how the particles are ordered in space.

47.The smallest repeating pattern from which the lattice is built in a crystalline solid is called (SZABMU MDCAT 2025)

  1. Crystallite
  2. Amorphous region
  3. Unit cell
  4. Crystal lattice
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Correct answer: (c) Unit cell

The unit cell is the smallest block whose repetition builds the whole lattice.

48.The factor that affects the lattice energy is: (NUMS MDCAT 2025)

  1. Charge to size ratio
  2. Shielding effect
  3. Crystal structure
  4. Atomic radius
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Correct answer: (a) Charge to size ratio

Lattice energy rises with the charge on the ions and falls with their size.

49.The ionic compound among the following with the highest lattice energy is: (SIBA MDCAT 2025)

  1. LiF
  2. NaCl
  3. KCl
  4. CsI
Show answer

Correct answer: (a) LiF

Lattice energy is greatest for the smallest ions, and lithium fluoride has the smallest pair here.

50.Which of the following compound has lower Lattice Energy? (SZABMU MDCAT 2025)

  1. LiCl
  2. KCl
  3. CaCl2
  4. CaH2O
Show answer

Correct answer: (b) KCl

Lattice energy falls as the ions get bigger, and the potassium ion is the largest of the singly charged ones here.

51.Most molecular crystals melt below: (NUMS MDCAT 2025)

  1. 200°C
  2. 280°C
  3. 330°C
  4. 480°C
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Correct answer: (a) 200°C

Molecular crystals are held by weak intermolecular forces, so they melt low, mostly under $200^{\circ}\mathrm{C}$.

Chemical Equilibrium

52.If the equilibrium expression of a reversible reaction is [C]2/[A][B] The balanced chemical equation should be (SZABMU MDCAT 2025)

  1. C=A+B
  2. 2C=A+B
  3. A+B=C
  4. A + B = 2C
Show answer

Correct answer: (d) A + B = 2C

The powers in the expression are the coefficients, so two moles of C are formed from one of A and one of B.

53.If ΔH for a reaction is positive, then by decreasing temperature, the reaction will (KMU MDCAT 2025)

  1. Move forward
  2. Move in reverse
  3. Have no effect
  4. Be both forward and reverse
Show answer

Correct answer: (b) Move in reverse

The forward reaction absorbs heat, so cooling shifts the equilibrium back the other way.

54.For which reaction, the value of Kc increases with increase in temperature? (SIBA MDCAT 2025)

  1. CH4 + O2 → CO2 + H2O
  2. NaOH + HCl → NaCl + H2O
  3. 2SO2 + O2 → 2SO3
  4. H2 + I2 → 2HI
Show answer

Correct answer: (d) H2 + I2 → 2HI

Only the formation of hydrogen iodide from its elements absorbs heat, and heating favours the endothermic direction.

55.In separate vessel of volume 2000 cm3 and 1500cm3, 6g of hydrogen and 28g of nitrogen are mixed in each vessel at 25°C, ammonia formed is? N2 + 3H2 ⇌ 2NH3 (SZABMU MDCAT 2025)

  1. More in 2 L vessel
  2. More in 1500 cm^3 vessel
  3. Equal in both vessel
  4. Cannot be predicted
Show answer

Correct answer: (b) More in 1500 cm^3 vessel

The forward reaction goes from four molecules to two, so the smaller vessel, at higher pressure, gives more ammonia.

56.Which of the following is basic buffer? (UHS MDCAT 2025)

  1. NH4OH/NH4Cl
  2. NaOH/NaCl
  3. NaOH/HCl
  4. H2CO3/NaHCO3
Show answer

Correct answer: (a) NH4OH/NH4Cl

A basic buffer is a weak base with the salt of that base, here ammonium hydroxide with ammonium chloride.

57.What happens when H+ is added to ammonium hydroxide and ammonium chloride buffer? (UHS MDCAT 2025)

  1. more ammonium hydroxide is formed
  2. reaction will move reverse
  3. reaction will move forward
  4. no effect on equilibrium
Show answer

Correct answer: (b) reaction will move reverse

The added protons are taken up by the ammonium hydroxide, driving the ionization back and holding the pH.

58.According to Le Chatelier's principle, in Haber's process yield of ammonia can be increased by: (SZABMU MDCAT 2025)

  1. decreasing pressure and increasing temperature
  2. increasing pressure and decreasing temperature
  3. increasing volume and decreasing temperature
  4. decreasing concentration of H2
Show answer

Correct answer: (b) increasing pressure and decreasing temperature

The forward reaction is exothermic and goes from four molecules to two, so high pressure and low temperature favour it.

Reaction Kinetics

59.Amount of energy needed to weaken the existing bonds to an extent that can be broken through collision is called: (UHS MDCAT 2025)

  1. Bond energy
  2. Activation energy
  3. Average energy
  4. Enthalpy
Show answer

Correct answer: (b) Activation energy

Activation energy is the least energy a colliding pair must carry for the reaction to proceed.

60.2A + B -> 3C + D which of the following does not express the reaction rate? (UHS MDCAT 2025)

  1. -d[B]/dt
  2. d[D]/dt
  3. -1/2 d[A]/dt
  4. -1/3 d[C]/dt
Show answer

Correct answer: (d) -1/3 d[C]/dt

C is formed, not consumed, so its rate term takes a plus sign.

61.Final equation for the representation of rate of reaction in term of concentration is called (UHS MDCAT 2025)

  1. Rate law
  2. Rate constant
  3. Reaction rate
  4. Reaction order
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Correct answer: (a) Rate law

The rate law is the equation giving the rate in terms of the concentrations of the reactants.

62.The formation of activated complex in a reaction is: (SIBA MDCAT 2025)

  1. Exothermic process
  2. Endothermic process
  3. Either endo or exo
  4. Always energy released
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Correct answer: (b) Endothermic process

Energy must be put in to reach the activated complex, so forming it absorbs heat.

63.At start of reaction: (SIBA MDCAT 2025)

  1. Average rate is high
  2. Instantaneous rate is high
  3. Both rates are same
  4. Both rates are slow
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Correct answer: (b) Instantaneous rate is high

At the start the concentration of reactant is greatest, so the instantaneous rate is at its highest.

64.Reaction having high activation energy are: (SZABMU MDCAT 2025)

  1. spontaneous
  2. fast
  3. slow
  4. always exothermic
Show answer

Correct answer: (c) slow

The higher the barrier, the fewer the collisions that carry enough energy, so the slower the reaction.

65.The rate of reaction (SZABMU MDCAT 2025)

  1. Increases as the reaction proceeds
  2. Decreases as the reaction proceeds
  3. Remains the same as the reaction proceeds
  4. May decrease or increase as the reaction proceeds
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Correct answer: (d) May decrease or increase as the reaction proceeds

It usually falls as the reactants are used up, but an autocatalytic reaction speeds up instead.

66.The rate of a chemical reaction changes with: (KMU MDCAT 2025)

  1. Concentration of reactant molecules
  2. Concentration of product molecules
  3. Concentration of both reactant and product
  4. Rate constant
Show answer

Correct answer: (a) Concentration of reactant molecules

The rate law is written in the concentrations of the reactants alone.

67.Orientation of molecule is more important in following cases except: (SZABMU MDCAT 2025)

  1. High Pressure
  2. complex molecules
  3. poly atomic molecules
  4. low pressure
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Correct answer: (d) low pressure

At low pressure the molecules are far apart and collisions are rare, so how they are turned matters least.

68.A reaction is first order with respect to A and third order with respect to B, the rate equation is: (NUMS MDCAT 2025)

  1. Rate = K[A][B]2
  2. Rate = K[A]2[B]
  3. Rate = K[A][B]3
  4. Rate = K[A]
Show answer

Correct answer: (c) Rate = K[A][B]3

The rate law carries each concentration to the power of its own order.

69.For a reaction A → Product, if concentration of A is doubled, product increases 4 times. The order of reaction will be: (NUMS MDCAT 2025)

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

Correct answer: (c) 2nd

The rate goes up by $2^2$ when the concentration doubles, so the order is two.

70.The order of chemical reaction is defined as: (SZABMU MDCAT 2025)

  1. The number of reactants involved in balanced equation
  2. The number of products formed in balanced equation
  3. The power to which the concentration of a reactant is raised in the rate equation
  4. The rate constant of the reaction
Show answer

Correct answer: (c) The power to which the concentration of a reactant is raised in the rate equation

The order in a reactant is the power to which its concentration is raised in the rate equation.

71.The specific rate constant (k) of a reaction is related to the concentration of reactants: (KMU MDCAT 2025)

  1. Directly
  2. Inversely
  3. Exponentially
  4. Independently
Show answer

Correct answer: (d) Independently

The rate constant depends on temperature and on the catalyst, never on how much reactant is present.

72.K is called specific rate constant because it is: (SIBA MDCAT 2025)

  1. Rate per unit concentration
  2. Temperature independent
  3. Depends on concentration
  4. Unitless
Show answer

Correct answer: (a) Rate per unit concentration

It is the rate when every reactant is at unit concentration, that is the rate per unit concentration.

Thermochemistry and Energetics of Chemical Reactions

73.Majority of reactions taking place at ordinary temperatures with -ΔH are (UHS MDCAT 2025)

  1. Endothermic
  2. Exothermic
  3. Thermally unstable
  4. Reversible
Show answer

Correct answer: (b) Exothermic

A negative enthalpy change means heat leaves the system, which is what exothermic means.

74.Select the exothermic reaction among the following: (NUMS MDCAT 2025)

  1. Thermal composition of P2O5
  2. Formation of atmospheric nitric oxide
  3. Burning of methane
  4. Sublimation of dry ice
Show answer

Correct answer: (c) Burning of methane

Burning methane gives out heat, so its enthalpy change is negative.

75.Select the spontaneous reaction from the following: (NUMS MDCAT 2025)

  1. Reaction of nitrogen and oxygen
  2. Emission of α-particles from polonium
  3. Thermal decomposition of marble
  4. Burning of paper
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Correct answer: (b) Emission of α-particles from polonium

Alpha emission needs no help from outside; the other three must be driven or lit.

76.Which of the following is NOT a state function? (SIBA MDCAT 2025)

  1. Enthalpy
  2. Work
  3. Internal energy
  4. Pressure
Show answer

Correct answer: (b) Work

Work depends on the path taken, so it is not fixed by the state of the system.

77.The heat of formation of CO and CO2 are -26.4 Kcal and -94.0 Kcal respectively. The heat of combustion of carbon monoxide according to Hess's Law will be: (SIBA MDCAT 2025)

  1. +26.4Kcal
  2. -67.6Kcal
  3. +94.0Kcal
  4. -120.4Kcal
Show answer

Correct answer: (b) -67.6Kcal

Burning carbon monoxide is the formation of carbon dioxide less the formation of the monoxide, $-94.0-(-26.4)$, or $-67.6\,\mathrm{kcal}$.

78.For endothermic reaction, enthalpy change is: (SZABMU MDCAT 2025)

  1. ΔHreactant>ΔHproduct
  2. ΔHreactant<ΔHproduct
  3. ΔHreactant=ΔHproduct
  4. ΔHreactant=ΔHproduct=0
Show answer

Correct answer: (b) ΔHreactant<ΔHproduct

An endothermic reaction takes heat in, so the products hold more enthalpy than the reactants.

79.If 100 KJ of heat is absorbed by the system and 40 KJ of work is done on the system what is the change of Internal energy? (UHS MDCAT 2025)

  1. -60 KJ
  2. +60 KJ
  3. -140 KJ
  4. +140 KJ
Show answer

Correct answer: (d) +140 KJ

Heat absorbed and work done on the system both add, so the internal energy rises by $140\,\mathrm{kJ}$.

80.An increase in the internal energy of a chemical system can lead to all EXCEPT: (KMU MDCAT 2025)

  1. An increase in temperature due to rise in kinetic energy of molecules
  2. A phase change such as melting or evaporation
  3. A chemical reaction if energy supplied is sufficient to break bonds
  4. An increase in temperature due to drop in kinetic energy of molecules
Show answer

Correct answer: (d) An increase in temperature due to drop in kinetic energy of molecules

Internal energy rises with the kinetic energy of the molecules, so a drop in that energy cannot raise the temperature.

Electrochemistry

81.Which of the following situations most clearly demonstrates a key characteristic of a Redox reaction? (UHS MDCAT 2025)

  1. Water boiling to steam
  2. Hydrogen gas reacting with chlorine to form hydrogen chloride gas
  3. Sodium chloride dissolving in water
  4. Ethanol evaporating at room temperature
Show answer

Correct answer: (b) Hydrogen gas reacting with chlorine to form hydrogen chloride gas

Hydrogen loses electrons to chlorine; the other three changes are physical.

82.Which of the following best identifies the redox reaction: (UHS MDCAT 2025)

  1. transfer of proton
  2. transfer of electron
  3. absorption of light
  4. exchange of ions
Show answer

Correct answer: (b) transfer of electron

Oxidation is loss of electrons and reduction is gain, so a redox reaction is an electron transfer.

83.In an electrolytic cell when the current passes through a solution, the anode is: (KMU MDCAT 2025)

  1. a positive electrode where oxidation occurs
  2. a negative electrode where oxidation occurs
  3. a negative electrode where reduction occurs
  4. a positive electrode where reduction occurs
Show answer

Correct answer: (a) a positive electrode where oxidation occurs

Oxidation always happens at the anode, and in an electrolytic cell the anode is the positive electrode.

84.The oxidation number of Cl in HClO2 is: (NUMS MDCAT 2025)

  1. +1
  2. +3
  3. +5
  4. +7
Show answer

Correct answer: (b) +3

Hydrogen is $+1$ and each oxygen $-2$, so chlorine must be $+3$ for the molecule to be neutral.

85.In the given reaction CH3OH -> HCOOH, oxidation state of carbon changes from: (SZABMU MDCAT 2025)

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

Correct answer: (b) -2 to +2

Carbon is $-2$ in methanol and $+2$ in formic acid, so it loses four electrons.

86.Which species contain an element with an oxidation number of +4? (SZABMU MDCAT 2025)

  1. CrO2-4
  2. MnO2-
  3. H2SO4
  4. Na2CO3
Show answer

Correct answer: (d) Na2CO3

Each oxygen is $-2$ and each sodium $+1$, so the carbon of the carbonate is $+4$.

87.When SHE is connected with Cu electrode using salt bridge and external wire: (SIBA MDCAT 2025)

  1. Cu reduces
  2. Cu+2 reduces
  3. H+ reduces
  4. H2 reduces
Show answer

Correct answer: (b) Cu+2 reduces

Copper stands above hydrogen in the electrochemical series, so the copper ions take the electrons and the copper electrode is the cathode.

88.In a standard hydrogen electrode, the platinum electrode: (SZABMU MDCAT 2025)

  1. Reacts with hydrogen
  2. Provide a surface for oxidation and reduction.
  3. Acts as a salt bridge.
  4. Provide voltage to the circuit.
Show answer

Correct answer: (b) Provide a surface for oxidation and reduction.

The platinum is inert; it only carries the electrons and offers a surface for the hydrogen.

Chemical Bonding

89.Correct arrangement of orbital according to size of hybridized orbitals? (UHS MDCAT 2025)

  1. sp>sp2>sp3
  2. sp3> sp> sp2
  3. sp2>sp>sp3
  4. sp3>sp2>sp
Show answer

Correct answer: (d) sp3>sp2>sp

More s character pulls the orbital in, so the sp orbital is the smallest and sp3 the largest.

90.In ethene molecule, each carbon atom has three hybridized sp2 orbitals which are: (KMU MDCAT 2025)

  1. Coplanar
  2. Tetrahedral
  3. Linear
  4. Pyramidal
Show answer

Correct answer: (a) Coplanar

Three sp2 orbitals lie in one plane at $120^{\circ}$ to each other.

91.In which of the following molecules does the central atom use sp2 hybridization? (KMU MDCAT 2025)

  1. PH3
  2. NH3
  3. BH3
  4. SbH3
Show answer

Correct answer: (c) BH3

Boron in $\mathrm{BH_3}$ has three bond pairs and no lone pair, so it is sp2 and trigonal planar.

92.In propene pi-bond is formed by sideway overlap of: (UHS MDCAT 2025)

  1. s-orbitals
  2. p-orbitals
  3. sp2 hybrid orbitals
  4. sp3 hybrid orbitals
Show answer

Correct answer: (b) p-orbitals

A pi bond is the sideways overlap of two unhybridized p orbitals.

93.The theories which explain the formation of sigma and pi bond are EXCEPT: (UHS MDCAT 2025)

  1. MOT
  2. VBT
  3. VSEPR
  4. CFT
Show answer

Correct answer: (c) VSEPR

VSEPR predicts shape from electron pair repulsion; it says nothing about how a bond is formed.

94.Bond order is equal to: (NUMS MDCAT 2025)

  1. Difference between number of bonding electrons and antibonding electrons
  2. The sum of number of bonding electrons and antibonding electrons
  3. Half of the difference between number of bonding electrons and antibonding electrons
  4. Quarter of the difference between number of bonding electrons and antibonding electrons
Show answer

Correct answer: (c) Half of the difference between number of bonding electrons and antibonding electrons

Bond order is half the difference between the bonding and the antibonding electrons.

95.How many sigma and pi bonds are present in maleic anhydride? (SZABMU MDCAT 2025)

  1. 5 sigma 3 pi
  2. 6 sigma 3 pi
  3. 7 sigma 2 pi
  4. 9 sigma 3 pi
Show answer

Correct answer: (d) 9 sigma 3 pi

Maleic anhydride has nine sigma bonds and three pi bonds, two of them in the carbonyl groups.

96.Molecules having one lone pair and three bond pairs have geometrical shape (UHS MDCAT 2025)

  1. Bent or angular
  2. Trigonal
  3. Trigonal pyramidal
  4. Trigonal planer
Show answer

Correct answer: (c) Trigonal pyramidal

Four electron pairs are arranged tetrahedrally, and with one of them a lone pair the shape of the molecule is trigonal pyramidal.

97.Which one of the following is a planar molecule? (KMU MDCAT 2025)

  1. NH3
  2. H2O
  3. BF3
  4. CH4
Show answer

Correct answer: (c) BF3

Three bond pairs and no lone pair on boron give a flat trigonal planar molecule.

98.Which of the following molecules have similar molecular shape? (SIBA MDCAT 2025)

  1. NH3 & AlCl3
  2. BCl3 & NH3
  3. AlCl3 & PCl3
  4. H2O & SnCl2
Show answer

Correct answer: (d) H2O & SnCl2

Both have two bond pairs and lone pairs on the central atom, so both are bent.

99.All of following have two bond pairs and show linear geometry except: (SIBA MDCAT 2025)

  1. SnCl2
  2. CS2
  3. HCN
  4. CO2
Show answer

Correct answer: (a) SnCl2

Tin in tin(II) chloride keeps a lone pair, which bends the molecule.

100.Which of the following has highest bond energy? (KMU MDCAT 2025)

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

Correct answer: (c) HF

The bond is shortest and strongest to the smallest halogen, so it is highest in hydrogen fluoride.

101.Correct order of bond energy will be: (SIBA MDCAT 2025)

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

Correct answer: (a) HCl>HBr>HI

The bond shortens as the halogen gets smaller, so it is strongest in hydrogen chloride of these three.

102.Which of the following molecule has non-polar covalent bond? (NUMS MDCAT 2025)

  1. Methyl chloride
  2. Methanol
  3. Carbon dioxide
  4. Tetrachloromethane
Show answer

Correct answer: (c) Carbon dioxide

Carbon dioxide is linear, so its two bond dipoles are equal and opposite and the molecule has no net dipole.

103.Value of electronegativity of atoms A and B are 1.20 and 4.0 respectively, the percent ionic character will be: (SIBA MDCAT 2025)

  1. 43%
  2. 50%
  3. 55%
  4. 73%
Show answer

Correct answer: (d) 73%

An electronegativity difference of $2.8$ puts the bond at about $73\%$ ionic character.

s- and p-Block Elements

104.The element with smallest value of ionization energy is (UHS MDCAT 2025)

  1. Li
  2. Al
  3. Ca
  4. Ba
Show answer

Correct answer: (d) Ba

Ionization energy falls down a group, and barium is the lowest of the four.

105.The most electronegative element in periodic table is: (KMU MDCAT 2025)

  1. F
  2. Cl
  3. N
  4. O
Show answer

Correct answer: (a) F

Fluorine is the most electronegative of all the elements.

106.Predict the element with lowest ionization energy: (NUMS MDCAT 2025)

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

Correct answer: (a) Mg

Ionization energy rises across a period, and magnesium lies furthest to the left of the four.

107.Select the group II element which has the highest atomic radius? (NUMS MDCAT 2025)

  1. Be
  2. Ca
  3. Ba
  4. Sr
Show answer

Correct answer: (c) Ba

The atomic radius grows down the group, and barium is the lowest of the four.

108.Which of the following element has least boiling point? (NUMS MDCAT 2025)

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

Correct answer: (d) Cs

Metallic bonding weakens down group I, so caesium boils lowest.

109.If ionization energy of an element is greater then: (SIBA MDCAT 2025)

  1. More is it's reducing power
  2. More is it's electropositivity
  3. Less is it's metallic character
  4. More is it's atomic radius
Show answer

Correct answer: (c) Less is it's metallic character

A high ionization energy means the atom holds its electrons tightly, so it is not metallic.

110.Which of the following best explains the reaction between Beryllium (Be) and Oxygen (O)? (KMU MDCAT 2025)

  1. Be burns vigorously with oxygen forming a layer of BeO, which accelerates the oxidation of remaining metal
  2. Be reacts with oxygen forming a layer of BeO, which protects the metal from further oxidation
  3. Be reacts slowly with oxygen to form a volatile oxide BeO, which evaporates quickly
  4. Be is the only alkaline earth metal that doesn't react with oxygen
Show answer

Correct answer: (b) Be reacts with oxygen forming a layer of BeO, which protects the metal from further oxidation

The oxide film that forms on beryllium sticks to the metal and seals it from further attack.

Transition Elements

111.Which one of the following is a coinage metal (UHS MDCAT 2025)

  1. Pd
  2. Cu
  3. Cd
  4. Hg
Show answer

Correct answer: (b) Cu

Copper, silver and gold are the coinage metals.

Fundamental Principles of Organic Chemistry

112.2-pentanone and 3-pentanone are examples of: (NUMS MDCAT 2025)

  1. Metamers
  2. Functional group isomers
  3. Tautomerism
  4. Position isomers
Show answer

Correct answer: (d) Position isomers

The two differ only in where the carbonyl group sits along the same chain.

113.Which compound will not show geometrical isomerism: (SIBA MDCAT 2025)

  1. But-2-ene
  2. 1,2-dimethylcyclopropane
  3. Pent-1-ene
  4. 1,3-dimethylcyclopentane
Show answer

Correct answer: (c) Pent-1-ene

Pent-1-ene has two hydrogens on its terminal carbon, so the two arrangements are the same.

114.Which one is not a type of stereoisomerism? (SIBA MDCAT 2025)

  1. Confirmational isomerism
  2. Optical isomerism
  3. Geometrical isomerism
  4. Metamerism
Show answer

Correct answer: (d) Metamerism

Metamerism is a kind of structural isomerism, not of stereoisomerism.

Chemistry of Hydrocarbons

115.What is general requirement for free radical substitution reaction of ethane and halogen? (UHS MDCAT 2025)

  1. low pressure
  2. low temperature
  3. high pressure
  4. heat and UV light
Show answer

Correct answer: (d) heat and UV light

Halogenation of an alkane needs heat or ultraviolet light to split the halogen into free radicals.

116.Consider the chlorination of methane to methyl chloride, the attack of chlorine free radical on methane, occurs in which phase? (KMU MDCAT 2025)

  1. Before initiation
  2. Initiation
  3. Propagation
  4. Termination
Show answer

Correct answer: (c) Propagation

A chlorine radical attacking methane is a propagation step: a radical is used and another is made.

117.The addition of water to propene in the presence of sulfuric acid produces: (KMU MDCAT 2025)

  1. Propane
  2. Propan-2-ol
  3. Butanol
  4. Ethanol
Show answer

Correct answer: (b) Propan-2-ol

The proton adds to give the more stable secondary carbocation, so the hydroxyl ends on the middle carbon.

118.Ratio of sigma bonds and pi bonds present in benzene are: (SIBA MDCAT 2025)

  1. 4:1
  2. 1:4
  3. 2:3
  4. 6:1
Show answer

Correct answer: (a) 4:1

Benzene has twelve sigma bonds and three pi bonds, a ratio of four to one.

119.Chlorination of benzene in the presence of Iron (III) chloride involves mechanism of: (UHS MDCAT 2025)

  1. Electrophilic addition
  2. Electrophilic Substitution
  3. Free radical Substitution
  4. Free radical halogenation
Show answer

Correct answer: (b) Electrophilic Substitution

Iron(III) chloride polarizes the chlorine into an electrophile, which then substitutes into the ring.

120.Which of the following is an electrophile in sulphonation? (NUMS MDCAT 2025)

  1. SO3H
  2. SO3
  3. SO2
  4. SO3+
Show answer

Correct answer: (b) SO3

Sulphur trioxide is itself electron poor at sulphur, so it attacks the ring without needing a catalyst.

121.Which reagent and condition are used to bring about the reaction shown? Toluene --> p-chloro toluene (SIBA MDCAT 2025)

  1. Cl2 in the dark
  2. Cl2 in the presence of AlCl3
  3. Cl2 in the presence of UV light
  4. Concentrated HCl heated under reflux
Show answer

Correct answer: (b) Cl2 in the presence of AlCl3

Aluminium chloride polarizes the chlorine into an electrophile for ring substitution; light would attack the side chain instead.

122.Conversion of dihaloalkane into alkyne does not involve (UHS MDCAT 2025)

  1. Addition
  2. Elimination
  3. Base
  4. Heat
Show answer

Correct answer: (a) Addition

A dihaloalkane loses two molecules of hydrogen halide to a strong base on heating, so the step is elimination, not addition.

123.Which of the following reagent is commonly used to prepare alkyne form vicinal dihalide? (SZABMU MDCAT 2025)

  1. H2 and catalyst
  2. KOH/NaNH2
  3. KMnO4
  4. LiAlH4
Show answer

Correct answer: (b) KOH/NaNH2

Two molecules of hydrogen halide are eliminated by alcoholic potash and then sodamide.

124.Terminal alkynes show acidic character due to: (UHS MDCAT 2025)

  1. Terminal carbon atoms are sp hybridized.
  2. Terminal carbon atoms are sp2 hybridized.
  3. Terminal carbon atoms are sp3 hybridized.
  4. Terminal carbon atoms show hydrogen bonding.
Show answer

Correct answer: (a) Terminal carbon atoms are sp hybridized.

The sp hybridized carbon holds its electrons close, so the terminal hydrogen leaves as a proton.

125.Which among the following will react with ammonical cuprous chloride: (SZABMU MDCAT 2025)

  1. 1-butene
  2. 1-butyne
  3. 2-butene
  4. 2-butyne
Show answer

Correct answer: (b) 1-butyne

A terminal alkyne is acidic enough to give a red copper acetylide; but-2-yne has no terminal hydrogen.

126.Acetylene reacts with hydrogen bromide to form: (NUMS MDCAT 2025)

  1. 2,2-Dibromoethane
  2. 1,1-Dibromoethane
  3. 1,2-Dibromoethane
  4. 1,1,2,2-Tetrabromoethane
Show answer

Correct answer: (b) 1,1-Dibromoethane

Both molecules of hydrogen bromide add by Markovnikov’s rule to the same carbon.

127.Generally the decreasing order of reactivity is: (NUMS MDCAT 2025)

  1. Alkane > Alkynes > Alkene
  2. Alkene < Alkynes < Alkanes
  3. Alkene > Alkynes > Alkanes
  4. Alkynes < Alkanes < Alkene
Show answer

Correct answer: (c) Alkene > Alkynes > Alkanes

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

128.Which one of the following is not a characteristic of benzene? (UHS MDCAT 2025)

  1. Aromaticity
  2. Stability
  3. to follow Huckle rule
  4. High reactivity
Show answer

Correct answer: (d) High reactivity

Delocalization makes benzene unusually stable, so it substitutes rather than reacting readily.

129.Addition of three molecules of chlorine into benzene prove that benzene has (SZABMU MDCAT 2025)

  1. double bonds
  2. non polar
  3. planar
  4. non planer
Show answer

Correct answer: (a) double bonds

Three molecules of chlorine add to it, which is what three double bonds would take.

130.The IUPAC name of Vinyl acetylene is: (SIBA MDCAT 2025)

  1. But-1-en-3-yne
  2. But-3-en-1-yne
  3. Pent-3-en-1-yne
  4. Pent-2-en-4-yne
Show answer

Correct answer: (a) But-1-en-3-yne

The chain of four carbons carries the double bond at position 1 and the triple bond at position 3.

Alkyl Halides

131.IUPAC name of (CH3)3 CCH2 Br is (UHS MDCAT 2025)

  1. 1-bromopentane
  2. 1-bromo-2,2,2-trimethylethane
  3. 1-bromo-2,2-dimethylpropane
  4. 2-bromopentane
Show answer

Correct answer: (c) 1-bromo-2,2-dimethylpropane

The longest chain is propane, with two methyl groups on carbon 2 and the bromine on carbon 1.

132.IUPAC name of chloroform is: (SZABMU MDCAT 2025)

  1. methylchloride
  2. methyltrichloride
  3. trichloromethane
  4. chloromethane
Show answer

Correct answer: (c) trichloromethane

Chloroform is methane with three of its hydrogens replaced, that is trichloromethane.

133.The order of reactivity of following R-X for SN reaction is: (SIBA MDCAT 2025)

  1. RF>RCl>RBr>RI
  2. RBr>RF>RCl>RI
  3. RCl>RF>RBr>RI
  4. RI>RBr>RCl>RF
Show answer

Correct answer: (d) RI>RBr>RCl>RF

The weakest carbon halogen bond breaks most readily, and that is the bond to iodine.

134.Racemic mixture formed in SN1 reaction is due to presence of empty: (NUMS MDCAT 2025)

  1. s-orbital
  2. p-orbital
  3. sp3-orbital
  4. sp2-orbital
Show answer

Correct answer: (b) p-orbital

The carbocation of the first step is flat, so the nucleophile can come in from either face.

135.Reaction of 2-Bromobutane with alcoholic KOH yields: (SZABMU MDCAT 2025)

  1. 2-Butanol
  2. 2-Butene
  3. 2-Butyne
  4. 1-Butanol
Show answer

Correct answer: (b) 2-Butene

Alcoholic potash favours elimination, so hydrogen bromide is lost and the alkene is left.

Alcohols and Phenols

136.Which of the following alcohols will give oily layer upon heating? (NUMS MDCAT 2025)

  1. 3-Methyl-2-butanol
  2. 2-Methyl-2-butanol
  3. 2-Butanol
  4. Ethyl alcohol
Show answer

Correct answer: (b) 2-Methyl-2-butanol

A tertiary alcohol reacts at once in the Lucas test, and the halide separates as an oily layer.

137.The order of reactivity of alcohol with respect to cleavage of C–O bond: (NUMS MDCAT 2025)

  1. Tertiary > Secondary > Primary
  2. Primary > Tertiary > Secondary
  3. Secondary > Tertiary > Primary
  4. Tertiary < Secondary < Primary
Show answer

Correct answer: (a) Tertiary > Secondary > Primary

The tertiary carbocation is the most stable, so the carbon oxygen bond breaks most readily there.

138.Rate of dehydration of alcohol is: (SIBA MDCAT 2025)

  1. 3°>2°>1°
  2. 1°>3°>2°
  3. 2°>3°>1°
  4. 3°>1°>2°
Show answer

Correct answer: (a) 3°>2°>1°

Dehydration goes through a carbocation, and the tertiary one is the most stable.

139.In a molecule of phenol, the carbon atom which is attached to -OH group is: (KMU MDCAT 2025)

  1. sp hybridized
  2. sp2 hybridized
  3. sp3 hybridized
  4. unhybridized
Show answer

Correct answer: (b) sp2 hybridized

That carbon is part of the aromatic ring, so it is sp2 hybridized.

140.Common name of 1,3 benzene diol is: (SZABMU MDCAT 2025)

  1. Pyrogallol
  2. Cresol
  3. Resorcinol
  4. Catechol
Show answer

Correct answer: (c) Resorcinol

Benzene-1,3-diol is resorcinol; the 1,2 isomer is catechol.

141.Which of the following best explains why phenol reacts with aqueous NaOH, but alcohols do not? (UHS MDCAT 2025)

  1. Phenol has a lower boiling point than alcohol.
  2. Alcohols contain a strong O-H bond that cannot be broken by weak bases.
  3. Phenol form hydrogen bonding that facilitates ionization.
  4. Phenol is weakly acidic due to resonance stabilization of phenoxide ion.
Show answer

Correct answer: (d) Phenol is weakly acidic due to resonance stabilization of phenoxide ion.

The ring delocalizes the charge of the phenoxide ion, so phenol is acidic enough to give a salt with sodium hydroxide.

142.Phenol differs from ethanol because it: (SIBA MDCAT 2025)

  1. Forms stronger hydrogen bonds to its aromatic ring
  2. Is more acidic because of resonance stabilized conjugate base
  3. Readily undergoes nucleophilic substitution at the -OH group
  4. Is completely insoluble in water due to its benzene ring
Show answer

Correct answer: (b) Is more acidic because of resonance stabilized conjugate base

The ring spreads the negative charge of the phenoxide ion, which ethanol cannot do, so phenol is the stronger acid.

Aldehydes and Ketones

143.Formalin is a mixture of: (NUMS MDCAT 2025)

  1. 40% HCHO, 8% CH3OH, 52% H2O
  2. 40% CH3CHO, 8% CH3OH, 50% H2O
  3. 40% CH3CHO, 8% C2H5OH, 50% H2O
  4. 45% HCHO, 8% C2H5OH, 50% H2O
Show answer

Correct answer: (a) 40% HCHO, 8% CH3OH, 52% H2O

Formalin is the $40\%$ aqueous solution of formaldehyde, with a little methanol to stop it polymerizing.

144.Acetaldehyde undergoes oxidation to produce acetic acid, In this reaction oxidizing agent used is: (UHS MDCAT 2025)

  1. HI
  2. LiAlH4
  3. K2Cr2O7
  4. NaBH4
Show answer

Correct answer: (c) K2Cr2O7

Acidified potassium dichromate oxidizes the aldehyde to the acid; the hydrides are reducing agents.

145.Methanol is produced by reduction of (UHS MDCAT 2025)

  1. Formaldehyde
  2. Acetaldehyde
  3. Propanal
  4. Propanone
Show answer

Correct answer: (a) Formaldehyde

Reducing the simplest aldehyde, formaldehyde, gives the simplest alcohol, methanol.

146.Polymerization of HCHO and CH3CHO occurs in the presence of: (NUMS MDCAT 2025)

  1. Conc. H2SO4
  2. Dil. H2SO4
  3. Conc. H2CO3
  4. Dil. H2CO3
Show answer

Correct answer: (a) Conc. H2SO4

Concentrated sulphuric acid polymerizes formaldehyde and acetaldehyde to trioxane and paraldehyde.

147.During Clemmenson reduction of aldehyde and ketone, carbonyl group into alkane group is carried out with: (SIBA MDCAT 2025)

  1. H2 and Pd
  2. LiAlH4
  3. Zn/Hg conc.HCl
  4. NH2-NH2/KOH
Show answer

Correct answer: (c) Zn/Hg conc.HCl

Clemmensen reduction uses zinc amalgam with concentrated hydrochloric acid to take the carbonyl down to a methylene group.

148.Which carbonyl carbon is more electrophilic: (SIBA MDCAT 2025)

  1. HCOOH
  2. HCHO
  3. CH3COCH3
  4. CH3COOH
Show answer

Correct answer: (b) HCHO

Formaldehyde has no alkyl group to push electrons towards the carbonyl carbon, so that carbon is the most electron poor.

Carboxylic Acids

149.The boiling point of carboxylic acids are relatively high due to: (NUMS MDCAT 2025)

  1. Increased molecular mass
  2. Intermolecular carbon bonding
  3. Intermolecular oxygen bonding
  4. Intermolecular hydrogen bonding
Show answer

Correct answer: (d) Intermolecular hydrogen bonding

Two molecules of the acid hydrogen bond into a dimer, so a great deal of heat is needed to separate them.

150.Carboxylic acid reacts with metal carbonate. The colorless gas evolved is: (NUMS MDCAT 2025)

  1. H2
  2. O2
  3. CO2
  4. CO
Show answer

Correct answer: (c) CO2

A carboxylic acid displaces carbon dioxide from a carbonate, as any acid does.

151.Fischer ESTERIFICATION Is which type of reaction: (UHS MDCAT 2025)

  1. Condensation
  2. Substitution
  3. Elimination
  4. Dehydrogenation
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Correct answer: (a) Condensation

An acid and an alcohol join with the loss of water, which makes esterification a condensation.

152.Carboxylic acid reacts with ammonia to form ammonium salts which on heating produces: (UHS MDCAT 2025)

  1. Carbonates
  2. Alkane
  3. Ester
  4. Amide
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Correct answer: (d) Amide

The ammonium salt loses water on strong heating and leaves the amide.

153.Which of the following compound will react with 2,2-dimethyl propanoic acid to produce ester? (NUMS MDCAT 2025)

  1. Ethanoic acid
  2. Propane
  3. Ethanol
  4. Propanone
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Correct answer: (c) Ethanol

An ester is an acid plus an alcohol, so ethanol is the reagent that gives one.

154.Formic acid reacts with ethanol in presence of acid catalyst produces: (SIBA MDCAT 2025)

  1. Ester
  2. Ether
  3. Acid anhydride
  4. Phenol
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Correct answer: (a) Ester

An acid and an alcohol with an acid catalyst give an ester and water.

155.Reduction of carboxylic acid by using lithium aluminiumhydride produce (SZABMU MDCAT 2025)

  1. Alcohol
  2. acid halide
  3. ester
  4. alkane
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Correct answer: (a) Alcohol

Lithium aluminium hydride reduces the carboxyl group all the way to a primary alcohol.

Macromolecules

156.The most abundant protein in animal kingdom forming 25–35% of body proteins is/are: (NUMS MDCAT 2025)

  1. Derived proteins
  2. Simple proteins
  3. Compound proteins
  4. Conjugated proteins
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Correct answer: (b) Simple proteins

Simple proteins yield only amino acids on hydrolysis, and they are the commonest kind in animals.

157.Protein present in connective tissues of human body is: (NUMS MDCAT 2025)

  1. Phosphoprotein
  2. Collagen
  3. Lecithin
  4. Cholesterol
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Correct answer: (b) Collagen

Collagen is the fibrous protein of tendon, ligament, skin and bone.

158.In human body Ferritin is used to store: (NUMS MDCAT 2025)

  1. P
  2. Ca
  3. Fe
  4. Zn
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Correct answer: (c) Fe

Ferritin is the iron store of the liver and the spleen.

159.In human body Ceruloplasmin acts as a carrier of: (NUMS MDCAT 2025)

  1. O2
  2. Zn
  3. Cu
  4. Fe
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Correct answer: (c) Cu

Ceruloplasmin is the copper carrying protein of the blood plasma.

Industrial Chemistry

160.Which of following adhesive is used to bond broken pieces of jewelry? (SIBA MDCAT 2025)

  1. Super glue
  2. Epoxy resin
  3. Silicon resin
  4. Starch
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Correct answer: (a) Super glue

Cyanoacrylate super glue sets in seconds on a thin joint, which suits broken jewellery.

161.Poly vinyl chloride (PVC) is the type of? (UHS MDCAT 2025)

  1. Homopolymer
  2. Thermosetting polymer
  3. Thermoplastic polymer
  4. Copolymor
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Correct answer: (a) Homopolymer

PVC is built from one monomer, vinyl chloride, so it is a homopolymer.

162.Which one is addition polymer? (SIBA MDCAT 2025)

  1. polyvinyl chloride
  2. nylon 6,6
  3. nylon 6,10
  4. polyester
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Correct answer: (a) polyvinyl chloride

Poly(vinyl chloride) is made by adding monomers with nothing eliminated; the nylons and polyesters are condensation polymers.

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