MDCAT 2020

MDCAT 2020 Past Paper with Answers (All Subjects)

199 MCQs from MDCAT 2020 in our bank, each with its correct answer and a solution. This is a recall-based collection gathered from students and past-paper books, not the complete official paper.

MDCAT 2020 by subject

Biology

1.Which of the following is not related to the enveloped virus? (PMC MDCAT 2020)

  1. They survive for a long time
  2. Their envelope is not sensitive to sunlight
  3. They are tolerant to antibodies
  4. Envelope is derived from host
Show answer

Correct answer: (b) Their envelope is not sensitive to sunlight

The lipid envelope is easily damaged by sunlight, drying and detergents.

2.The complete, mature and infection virus particle is known as: (PMC MDCAT 2020)

  1. Venome
  2. Genome
  3. Virion
  4. Capsid
Show answer

Correct answer: (c) Virion

A complete infectious virus particle is a virion.

3.Numerous opportunist diseases might attack people suffering from the following diseases? (PMC MDCAT 2020)

  1. Measles
  2. Influenza
  3. Hepatitis A
  4. AIDS
Show answer

Correct answer: (d) AIDS

With the helper T cells destroyed, organisms that a healthy body ignores become deadly.

4.Which of the following is NOT TRUE about Human Immunodeficiency virus (HIV)? (PMC MDCAT 2020)

  1. It is a retrovirus
  2. It is surrounded by an envelope
  3. It does not cause AIDS
  4. It causes deficiency of the human immune system
Show answer

Correct answer: (c) It does not cause AIDS

HIV is the cause of AIDS; the other three statements are true of it.

5.The end product in anaerobic respiration is: (PMC MDCAT 2020)

  1. Ethanol and Carbon dioxide
  2. Lactate
  3. Pyruvate
  4. Both A and B
Show answer

Correct answer: (d) Both A and B

Yeast ferments to ethanol and carbon dioxide, muscle to lactate.

6.The end product of glycolysis in acrobic respiration is (PMC MDCAT 2020)

  1. Ethanol and carbon dioxide
  2. Lactate
  3. Pyruvate
  4. Acetyl CoA
Show answer

Correct answer: (c) Pyruvate

With oxygen present, glycolysis ends at pyruvate, which then enters the mitochondrion.

7.Water acts as a universal solvent because of: (PMC MDCAT 2020)

  1. Heat of vaporization
  2. Hydrogen bonding
  3. High polarity
  4. Cohesion and adhesion
Show answer

Correct answer: (c) High polarity

The water molecule is strongly polar, so it pulls ions apart and surrounds them.

8.Lipids store double the amount of energy as compared to carbohydrates because of: (PMC MDCAT 2020)

  1. High proportion of oxygen
  2. High C-O ratio
  3. Low proportion of Carbon
  4. High proportion of C-H
Show answer

Correct answer: (d) High proportion of C-H

A fat is rich in carbon hydrogen bonds and poor in oxygen, so more energy is released when it is oxidized.

9.Which of the following is an unsaturated fatty acid? (PMC MDCAT 2020)

  1. Oleic acid
  2. Palmitic acid
  3. Butyric acid
  4. Acetic acid
Show answer

Correct answer: (a) Oleic acid

Oleic acid has one double bond in its chain; the others are saturated.

10.Transcription is the process in which an RNA copy of the DNA sequence and coding the gene is produced with the help of an enzyme called: (PMC MDCAT 2020)

  1. DNA polymerase
  2. RNA polymerase
  3. DNA transcriptase
  4. RNA transcriptase
Show answer

Correct answer: (b) RNA polymerase

RNA polymerase reads the template strand and builds the RNA copy.

11.Which statement correctly describes the transcription of DNA? (PMC MDCAT 2020)

  1. It produces amino acids
  2. It produces messenger RNA
  3. It results in increased DNA synthesis
  4. It is a semi conservative process
Show answer

Correct answer: (b) It produces messenger RNA

Transcription copies a gene into messenger RNA.

12.NAD is an example of: (PMC MDCAT 2020)

  1. Mononucleotide
  2. Dinucleotide
  3. Trinucleotide
  4. Tetranucleotide
Show answer

Correct answer: (b) Dinucleotide

NAD is two nucleotides joined through their phosphates.

13.Which one of the following is found in both messenger RNA and DNA of a mammalian cell? (PMC MDCAT 2020)

  1. Double helical structure
  2. Ribose sugar
  3. Thymine
  4. Sugar – phosphate backbone
Show answer

Correct answer: (d) Sugar – phosphate backbone

Both are built on a backbone of alternating sugar and phosphate.

14.What is the effect of enzyme DNA ligase? (PMC MDCAT 2020)

  1. DNA is broken up at specific sites
  2. DNA fragments are joined together
  3. DNA replication occurs
  4. DNA transcription occurs
Show answer

Correct answer: (b) DNA fragments are joined together

DNA ligase seals the sugar phosphate backbone between two fragments.

15.Which property of water helps to maintain the integrity of lipid-containing membranes? (PMC MDCAT 2020)

  1. Specific Heat Capacity
  2. Hydrogen Bonding
  3. Cohesion and Adhesion
  4. Hydrophobic exclusion
Show answer

Correct answer: (d) Hydrophobic exclusion

The fatty tails are driven together away from water, and that is what holds the bilayer.

16.In which type of cells, cell wall is not present? (PMC MDCAT 2020)

  1. Plant cells
  2. Fungal cells
  3. Bacterial cells
  4. Liver cells
Show answer

Correct answer: (d) Liver cells

Animal cells have only a plasma membrane; plants, fungi and bacteria all have walls.

17.Tissue is a (PMC MDCAT 2020)

  1. group of cells
  2. group of organs
  3. group of tissues
  4. group of organisms
Show answer

Correct answer: (a) group of cells

A tissue is a group of similar cells doing the same work.

18.Which of the following is TRUE about the structure of a typical bacterium? (PMC MDCAT 2020)

  1. It has cell wall
  2. It has cytoplasm
  3. It has genetic material
  4. All of the above
Show answer

Correct answer: (d) All of the above

Every bacterium has a wall, cytoplasm and a chromosome.

19.70S sized ribosomes are found in the cytoplasm of: (PMC MDCAT 2020)

  1. Algae
  2. Fungi
  3. Protozoans
  4. Bacteria
Show answer

Correct answer: (d) Bacteria

Bacteria have 70S ribosomes; the eukaryotic ones are 80S.

20.Select a method which causes the oxidation of chemical constituent of a bacterial cell: (PMC MDCAT 2020)

  1. Steam
  2. Dry heat
  3. Filtration
  4. Radiation
Show answer

Correct answer: (b) Dry heat

Dry heat kills by oxidizing the constituents of the cell; moist heat coagulates its proteins.

21.Suggest which among the following is not a function attributed to endoplasmic reticulum? (PMC MDCAT 2020)

  1. Detoxification of poisons and drugs
  2. Digestion/egestion of foreign materials outside the cell
  3. Manufacture of fat and lipid molecules
  4. Biogenesis of membrane proteins
Show answer

Correct answer: (b) Digestion/egestion of foreign materials outside the cell

Digestion of engulfed material is the work of the lysosome.

22.Which of the following cell organelles involved in the synthesis of cell wall and middle lamella? (PMC MDCAT 2020)

  1. Endoplasmic reticulum
  2. Golgi apparatus
  3. Lysosomes
  4. Peroxisomes
Show answer

Correct answer: (b) Golgi apparatus

The Golgi apparatus makes the vesicles that carry wall material to the cell plate.

23.The membrane separating the vacuole from cytoplasm is called (PMC MDCAT 2020)

  1. Cristae
  2. Cisternae
  3. Tonoplast
  4. Vacuolar membrane
Show answer

Correct answer: (c) Tonoplast

The membrane round a plant vacuole is the tonoplast.

24.At what phase the DNA content of a cell is doubled? (PMC MDCAT 2020)

  1. Prophase
  2. Interphase
  3. Anaphase
  4. Telophase
Show answer

Correct answer: (b) Interphase

DNA is replicated in the S phase of interphase, before division begins.

25.The cells in our body are all genetically identical, apart from the: (PMC MDCAT 2020)

  1. Somatic cells
  2. Reproductive cells
  3. Muscle fibers
  4. White blood cells
Show answer

Correct answer: (b) Reproductive cells

Meiosis and crossing over make every gamete different.

26.The particular array of chromosomes that an individual possesses is called its: (PMC MDCAT 2020)

  1. Genotype
  2. Phenotype
  3. Karyotype
  4. Allele
Show answer

Correct answer: (c) Karyotype

The number, size and shape of the chromosomes of an individual is its karyotype.

27.Which of the following neurotransmitters function, both as neurotransmitter and hormones, decreasing our perception of pain? (PMC MDCAT 2020)

  1. Epinephrine
  2. Serotonin
  3. Dopamine
  4. Endorphins
Show answer

Correct answer: (d) Endorphins

Endorphins are the brain’s own opiates and damp down the sense of pain.

28.Which one of the following is common to all neurons? (PMC MDCAT 2020)

  1. A cell body which contains a nucleus
  2. A thick myelin sheath
  3. Presence of node of Ranvier
  4. Presence of Schwann cells
Show answer

Correct answer: (a) A cell body which contains a nucleus

Every neuron has a cell body with a nucleus; myelin, nodes and Schwann cells belong only to some.

29.Neurons are cells adapted for the rapid transmission of electrical impulses. To do this, they have long thin processes called: (PMC MDCAT 2020)

  1. Axons
  2. Dendrites
  3. Myelin sheath
  4. Schwann cell
Show answer

Correct answer: (a) Axons

The long process that carries the impulse away is the axon.

30.A _____ is a junction between two neurons or between a motor neuron and a muscle cell: (PMC MDCAT 2020)

  1. Impulse
  2. Synapse
  3. Axon
  4. Cleft
Show answer

Correct answer: (b) Synapse

That junction is the synapse.

31.Enzymes work by lowering the ______ of the reactions they catalyse: (PMC MDCAT 2020)

  1. Kinetic energy
  2. Activation energy
  3. Heat energy
  4. Potential energy
Show answer

Correct answer: (b) Activation energy

An enzyme offers a path over a lower energy barrier.

32.Lock and Key Model for enzyme action propose by Emil Fischer suggests that: (PMC MDCAT 2020)

  1. Enzymes are unbiased for the substrate
  2. Enzymes can modify their active sites
  3. Enzymes are restricted to one reaction type
  4. An enzyme can catalyze variety of reactions
Show answer

Correct answer: (c) Enzymes are restricted to one reaction type

The lock and key model treats the active site as a rigid shape that only its own substrate fits.

33.Most enzymes have an optimum temperature of around: (PMC MDCAT 2020)

  1. 30 C
  2. 40 C
  3. 50 C
  4. 20 C
Show answer

Correct answer: (b) 40 C

Human enzymes work fastest near body temperature.

34.______ occurs because natural selection gives some alleles a better chance of survival than others: (PMC MDCAT 2020)

  1. Fitness
  2. Evolution
  3. Crossing over
  4. Artificial Selection
Show answer

Correct answer: (b) Evolution

Evolution follows from some alleles leaving more descendants than others.

35.Which one of the following represents the changes that occur in the ovary and the uterus approximately every 28 days involving ovulation with the breakdown and loss of the lining of the uterus? (PMC MDCAT 2020)

  1. Ovulation
  2. Menstrual cycle
  3. Uterine cycle
  4. Embryo formation
Show answer

Correct answer: (b) Menstrual cycle

That monthly round of ovulation and shedding is the menstrual cycle.

36.Which of the following hormones of the pituitary gland regulates the menstrual cycle? (PMC MDCAT 2020)

  1. Follicle Stimulating hormone and Estrogen
  2. Luteinizing hormone and Estrogen
  3. Follicle Stimulating hormone and Luteinizing hormone
  4. Estrogen and Progesterone
Show answer

Correct answer: (c) Follicle Stimulating hormone and Luteinizing hormone

FSH and LH from the anterior pituitary drive the ovarian cycle.

37.Which body function is controlled through a positive feedback mechanism? (PMC MDCAT 2020)

  1. Labor contractions
  2. Body temperature
  3. Insulin production
  4. Thyroxine release
Show answer

Correct answer: (a) Labor contractions

Each contraction of labour drives the head further down, which brings on a stronger contraction still.

38.Which of the following diseases is sexually transmitted? (PMC MDCAT 2020)

  1. Tuberculosis
  2. AIDS
  3. Dengue Fever
  4. Cholera
Show answer

Correct answer: (b) AIDS

AIDS is passed by sexual contact as well as by blood.

39.Which one of the following are “myogenic” type of muscles? (PMC MDCAT 2020)

  1. Glandular muscles
  2. Cardiac muscles
  3. Skeletal muscles
  4. Smooth muscles
Show answer

Correct answer: (b) Cardiac muscles

Cardiac muscle sets its own rhythm, so its contraction is myogenic.

40.Which one of the following muscles are considered as “Voluntary muscles”? (PMC MDCAT 2020)

  1. Smooth muscles
  2. Cardiac muscles
  3. Skeletal muscles
  4. Glandular muscles
Show answer

Correct answer: (c) Skeletal muscles

Skeletal muscle alone is under conscious control.

41.What do we call the cell surface membrane of a muscle fibre? (PMC MDCAT 2020)

  1. Sarcolemma
  2. Plasma membrane
  3. Sarcoplasm
  4. Myofibrils
Show answer

Correct answer: (a) Sarcolemma

The membrane of a muscle fibre is the sarcolemma.

42.In ‘Complete Dominance’: (PMC MDCAT 2020)

  1. Different alleles of a gene are both expressed in heterozygous condition
  2. One allele (R) is completely dominant over the other (r) and the presence of the recessive allele is functionally hidden, so the heterozygote (Rr) has the same round phenotype as (RR) homozygote.
  3. The phenotype of the heterozygote is intermediate between phenotypes of the two homozygotes
  4. Gene mutations may produce many different alleles of a gene
Show answer

Correct answer: (b) One allele (R) is completely dominant over the other (r) and the presence of the recessive allele is functionally hidden, so the heterozygote (Rr) has the same round phenotype as (RR) homozygote.

Under complete dominance the heterozygote looks exactly like the dominant homozygote.

43.“Law of independent assortment” states: (PMC MDCAT 2020)

  1. That each pair of alleles assort independently of other pairs of alleles during gamete formation
  2. That alleles of each pair of contrasting trait have unequal probability to assort with the alleles of other pair
  3. That the two coexisting alleles for each trait segregate (separate) from each other at meiosis so that each gamete receives only one of the two alleles
  4. That pertain to inheritance of single trait (monohybrid cross)
Show answer

Correct answer: (a) That each pair of alleles assort independently of other pairs of alleles during gamete formation

Each pair of alleles goes into the gametes independently of every other pair.

44.______ alleles both have an effect on the phenotype of a heterozygous organism: (PMC MDCAT 2020)

  1. Dominant
  2. Recessive
  3. Co-dominant
  4. Multiple
Show answer

Correct answer: (c) Co-dominant

Codominant alleles are both expressed in the heterozygote.

45.Phenotype is: (PMC MDCAT 2020)

  1. The genetic component i.e. the genes in an individual for a particular trait
  2. Partner of gene pair
  3. The form of appearance of a trait
  4. The position of a gene on the chromosome
Show answer

Correct answer: (c) The form of appearance of a trait

The phenotype is what shows; the genotype is what is carried.

46.Which traits are most likely to affect men than women? (PMC MDCAT 2020)

  1. X linked recessive
  2. X linked dominant
  3. Autosomal dominant
  4. Autosomal recessive
Show answer

Correct answer: (a) X linked recessive

A man has only one X, so a single recessive allele on it shows at once.

47.Haemophilia occurs because of: (PMC MDCAT 2020)

  1. Mutation in an autosome
  2. Mutation of Y-chromosome
  3. Mutation of X-chromosome
  4. Deficiency of iron
Show answer

Correct answer: (c) Mutation of X-chromosome

The gene for the missing clotting factor lies on the X chromosome.

48.During meiosis, the homologous chromosomes come together and form pairs, this process is called: (PMC MDCAT 2020)

  1. Linkage
  2. Synapsis
  3. Pairing
  4. Crossing over
Show answer

Correct answer: (b) Synapsis

The pairing of homologues at prophase I is synapsis.

49.Which of the following blood vessels have the highest pressure of blood? (PMC MDCAT 2020)

  1. Aorta
  2. Pulmonary arteries
  3. Pulmonary veins
  4. Vena cava
Show answer

Correct answer: (a) Aorta

The aorta takes the full force of the left ventricle, so the pressure there is highest.

50.The only vein in human carrying oxygenated blood is: (PMC MDCAT 2020)

  1. Femoral
  2. Pulmonary
  3. Real
  4. Iliac
Show answer

Correct answer: (b) Pulmonary

The pulmonary vein brings oxygenated blood back from the lungs.

51.Regarding structure of the human heart, Chordae Tendinae are present in: (PMC MDCAT 2020)

  1. Atria
  2. Pulmonary valve
  3. Ventricles
  4. Aortic valve
Show answer

Correct answer: (c) Ventricles

The chordae tendineae run from the papillary muscles of the ventricles to the cusps of the valves.

52.The cells which play a very important role in developing immunity are: (PMC MDCAT 2020)

  1. Monocytes
  2. Neutrophils
  3. Lymphocytes
  4. Thrombocytes
Show answer

Correct answer: (c) Lymphocytes

The lymphocytes, B cells and T cells, carry the specific immune response.

53.Antibodies are manufactured in: (PMC MDCAT 2020)

  1. T Lymphocytes
  2. Red Blood Cells
  3. Platelets
  4. B Lymphocytes
Show answer

Correct answer: (d) B Lymphocytes

B lymphocytes turn into plasma cells and those make the antibody.

54.Autoimmune diseases act as the principle of: (PMC MDCAT 2020)

  1. Self against antigens
  2. Antigen against self
  3. Self against self
  4. Antigen self destroyed
Show answer

Correct answer: (c) Self against self

In an autoimmune disease the immune system fails to tell self from foreign and attacks the body.

55.The active uptake of sodium in the ascending limb or thick loop of Henle is promoted by the action of: (PMC MDCAT 2020)

  1. Aldosterone
  2. Thyroxine
  3. ADH
  4. Cortisone
Show answer

Correct answer: (a) Aldosterone

Aldosterone drives the sodium pumps of the nephron.

56.The excretion of hypertonic urine in humans is associated best with the: (PMC MDCAT 2020)

  1. Glomerular capsule
  2. Proximal convoluted tubule
  3. Loop of Henle
  4. Distal convoluted tubule
Show answer

Correct answer: (c) Loop of Henle

The loop of Henle builds the salt gradient of the medulla that lets water be drawn from the collecting duct.

57.In humans, the temperature regulation control center is located in: (PMC MDCAT 2020)

  1. Kidneys
  2. Brain
  3. Lungs
  4. Liver
Show answer

Correct answer: (b) Brain

The hypothalamus holds the thermostat of the body.

58.When the temperature of the surrounding environment rises, body responds by: (PMC MDCAT 2020)

  1. Vasoconstriction
  2. Vasodilation
  3. Shivering
  4. Raising body hairs
Show answer

Correct answer: (b) Vasodilation

Widening the skin arterioles brings more blood to the surface, where the heat is lost.

59.As an excretory organ, liver: (PMC MDCAT 2020)

  1. Detoxifies many chemical poisons
  2. Breaks down ammonia for excretion by the kidneys
  3. Produces urea and uric acids from the nitrogen of amino acids
  4. All of the above
Show answer

Correct answer: (d) All of the above

The liver detoxifies, deaminates the amino acids and makes the urea the kidney then excretes.

60.Gel electrophoresis is a technique: (PMC MDCAT 2020)

  1. Employed by forensic scientist to assist in the identification of the individuals by their respective type of DNA
  2. Collect all the genes found in one complete set of chromosome
  3. Is a technique to separate different sizeds fragment of charge bearing polymers (proteins, RNA or DNA)
  4. Grows single cell or a group of cells in a glass ware on artificial medium under aseptic conditions
Show answer

Correct answer: (c) Is a technique to separate different sizeds fragment of charge bearing polymers (proteins, RNA or DNA)

Gel electrophoresis pulls charged fragments through a gel, and the small ones travel furthest.

61.Which of the following is the components / tools of recombinant DNA technology? (PMC MDCAT 2020)

  1. Gene of interest
  2. Molecular scissors
  3. Molecular glue and expression system
  4. All of the above
Show answer

Correct answer: (d) All of the above

The gene, restriction enzymes to cut it, ligase to join it and a host to express it are all needed.

62.The DNA that has been altered and which now contains length of nucleotides from two different organisms is called a: (PMC MDCAT 2020)

  1. Plasmid
  2. Combined DNA
  3. Vector
  4. Recombinant DNA
Show answer

Correct answer: (d) Recombinant DNA

DNA carrying lengths from two organisms is recombinant DNA.

63.It is a method for rapid production of a very large number of copies of a particular fragment of DNA: (PMC MDCAT 2020)

  1. Gel electrophoresis
  2. Polymerase chain reaction
  3. DNA extraction
  4. Recombination
Show answer

Correct answer: (b) Polymerase chain reaction

The polymerase chain reaction doubles the chosen fragment at every cycle.

64.Transgenic organisms: (PMC MDCAT 2020)

  1. Have a foreign gene inserted into them
  2. Have an important role in the large scale production of medicinal products
  3. Are considered beneficial to humans
  4. All of the above
Show answer

Correct answer: (d) All of the above

A transgenic organism carries a gene from another species, and such organisms make insulin and other medicines.

Chemistry

65.The mass of one molecule of $\mathrm{O_2}$ is: (MDCAT 2020)

  1. $6.02\times10^{23}/32$ g
  2. $32/6.02\times10^{23}$ g
  3. 32 g
  4. 0.32 g
Show answer

Correct answer: (b) $32/6.02\times10^{23}$ g

One mole of $\mathrm{O_2}$ weighs 32 g and holds $6.02\times10^{23}$ molecules, so one molecule is the quotient of the two.

66.The number of moles of $\mathrm{CO_2}$ which contain 8.0 g of oxygen is: (MDCAT 2020)

  1. 1.0
  2. 4.50
  3. 0.50
  4. 0.25
Show answer

Correct answer: (d) 0.25

One mole of $\mathrm{CO_2}$ carries 32 g of oxygen, so 8.0 g of oxygen belongs to a quarter of a mole.

67.One mole of any substance contains how many particles? (MDCAT 2020)

  1. $6.02\times10^{23}$
  2. $6.02\times10^{-23}$
  3. $6.02\times10^{32}$
  4. $3.01\times10^{23}$
Show answer

Correct answer: (a) $6.02\times10^{23}$

That count is Avogadro's number.

68.What is the number of particles in 0.25 moles of $\mathrm{CO_2}$? (MDCAT 2020)

  1. $6.022\times10^{23}$
  2. $1.505\times10^{23}$
  3. $2.00\times10^{23}$
  4. $3.01\times10^{23}$
Show answer

Correct answer: (b) $1.505\times10^{23}$

$0.25\times6.022\times10^{23}=1.505\times10^{23}$.

69.The empirical formula of Glucose C6H12O6 is: (PMC MDCAT 2020)

  1. C6H12O6
  2. CHO
  3. CH2O
  4. CH2O2
Show answer

Correct answer: (c) CH2O

Dividing the subscripts by six leaves $\mathrm{CH_2O}$.

70.In a vessel, 10 g N2, 10 g H2 and 10g O2 are present. Which one will have least number of atoms? (PMC MDCAT 2020)

  1. H2
  2. N2
  3. O2
  4. Both H2 and N2
Show answer

Correct answer: (c) O2

Ten grams is $5$ moles of hydrogen but only $0.31$ of oxygen, so the oxygen has fewest atoms.

71.The efficiency of chemical reaction can be expressed as: (PMC MDCAT 2020)

  1. Theoretical yield
  2. Actual yield
  3. % yield
  4. Maximum yield
Show answer

Correct answer: (c) % yield

The percentage yield compares what was got with what was possible.

72.The lightest positive rays are obtained from: (MDCAT 2020)

  1. hydrogen gas
  2. helium
  3. neon
  4. air
Show answer

Correct answer: (a) hydrogen gas

The positive ray is an ion of the gas in the tube, and the hydrogen ion is the lightest there is.

73.The amount of energy associated with a quantum of radiation is directly proportional to its: (MDCAT 2020)

  1. photon
  2. wavelength
  3. frequency
  4. velocity
Show answer

Correct answer: (c) frequency

$E=h

74.The maximum number of electrons that can be placed in one orbital is: (MDCAT 2020)

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

Correct answer: (b) 2

The Pauli exclusion principle allows two electrons of opposite spin in one orbital.

75.Quantum number values for ‘2p’ orbitals are: (PMC MDCAT 2020)

  1. n=2, l=1
  2. n=1, l=2
  3. n=1, l=0
  4. n=2, l=0
Show answer

Correct answer: (a) n=2, l=1

The 2p orbital has $n=2$ and $l=1$.

76.The relationship between quantum number n and l is: (PMC MDCAT 2020)

  1. n = l – 1
  2. l = n – 2
  3. l = n – 1
  4. n = l – 2
Show answer

Correct answer: (c) l = n – 1

For a given $n$, $l$ runs from zero up to $n-1$.

77.Which of the following orbitals will be filled before $4p$? (MDCAT 2020)

  1. $4s$
  2. $2p$
  3. $3d$
  4. $5s$
Show answer

Correct answer: (c) $3d$

By the $(n+l)$ rule the order runs $4s$, $3d$, $4p$, so $3d$ fills first of these.

78.Which pair has 1 electron in it’s ‘s’ orbital? (PMC MDCAT 2020)

  1. Li & Fe
  2. Na & Cr
  3. K & Mn
  4. H & He
Show answer

Correct answer: (b) Na & Cr

Sodium is $3s^1$ and chromium $4s^1$, each with a single s electron in its outer shell.

79.Half of atmospheric pressure is: (MDCAT 2020)

  1. 400 torr
  2. 50662 Pa
  3. 1013 Pa
  4. 6.5 pounds
Show answer

Correct answer: (b) 50662 Pa

One atmosphere is 101325 Pa, so half of it is 50662 Pa.

80.At constant pressure, at which temperature will the volume of a gas become twice its volume at $0^\circ$C? (MDCAT 2020)

  1. $100^\circ$C
  2. $200^\circ$C
  3. $273^\circ$C
  4. $373^\circ$C
Show answer

Correct answer: (c) $273^\circ$C

Volume goes as the absolute temperature, so it doubles when 273 K becomes 546 K, which is $273^\circ$C.

81.A graph between volume and temperature gives a straight line which cuts the temperature axis at: (MDCAT 2020)

  1. $273^\circ$C
  2. $-273^\circ$C
  3. $540^\circ$C
  4. $0^\circ$C
Show answer

Correct answer: (b) $-273^\circ$C

Extrapolated to zero volume the line meets the axis at absolute zero, $-273^\circ$C.

82.The starting point of the Kelvin scale is: (MDCAT 2020)

  1. 0 K
  2. 100 K
  3. $-210$ K
  4. $-273.15$ K
Show answer

Correct answer: (a) 0 K

The Kelvin scale begins at absolute zero, which is 0 K by definition.

83.The expression $PV=nRT$ represents the: (MDCAT 2020)

  1. Dalton's law
  2. Avogadro's law
  3. general gas equation
  4. van der Waals equation
Show answer

Correct answer: (c) general gas equation

It is the ideal or general gas equation, got by combining the laws of Boyle, Charles and Avogadro.

84.According to the general gas equation, density of an ideal gas depends upon: (PMC MDCAT 2020)

  1. Pressure
  2. Temperature
  3. Molar Mass
  4. All of these
Show answer

Correct answer: (d) All of these

$d=PM/RT$ carries the pressure, the temperature and the molar mass together.

85.The actual volume of gas molecules is considered negligible at following pressures: (PMC MDCAT 2020)

  1. 2 atm
  2. 4 atm
  3. 6 atm
  4. 8 atm
Show answer

Correct answer: (a) 2 atm

The lower the pressure the further apart the molecules, so their own volume counts for least at $2\,\mathrm{atm}$.

86.CO2 and SO2 both are tri-atomic molecules but heat of vaporization of SO2 is greater than that of CO2 due to: (PMC MDCAT 2020)

  1. High electronegativity of S
  2. Greater size of SO2
  3. SO2 is polar and CO2 is non-polar
  4. SO2 is more acidic than CO2
Show answer

Correct answer: (c) SO2 is polar and CO2 is non-polar

Sulphur dioxide is bent and polar, so its molecules attract each other far more strongly.

87.Vapour pressure is independent of which factor? (MDCAT 2020)

  1. temperature
  2. intermolecular forces
  3. density of the liquid
  4. surface area of the liquid
Show answer

Correct answer: (d) surface area of the liquid

A wider surface evaporates more molecules but condenses just as many, so the equilibrium vapour pressure is unchanged.

88.Which of the following has the lowest vapour pressure at 20 degrees Centigrade? (PMC MDCAT 2020)

  1. Diethyl ether
  2. Chloroform
  3. Carbon tetrachloride
  4. Water
Show answer

Correct answer: (d) Water

Water is hydrogen bonded, so far fewer of its molecules escape than of the others.

89.Solid water is expanded how many times when compared with the same mass of liquid water? (MDCAT 2020)

  1. 9
  2. 10
  3. 75
  4. 2
Show answer

Correct answer: (a) 9

The open hydrogen-bonded cage of ice takes about 9% more room, which is why ice floats and pipes burst.

90.Some substances lack a definite heat of fusion. These substances are: (MDCAT 2020)

  1. isomorphs
  2. polymorphs
  3. amorphous solids
  4. crystalline solids
Show answer

Correct answer: (c) amorphous solids

Amorphous solids have no ordered lattice to break down at one temperature, so they soften over a range instead of melting sharply.

91.Which of the following substances has giant covalent structure? (PMC MDCAT 2020)

  1. Iodine crystal
  2. Solid CO2
  3. Silica
  4. White phosphorus
Show answer

Correct answer: (c) Silica

Silica is bonded covalently right through the crystal.

92.The Lattice energy is also called as: (PMC MDCAT 2020)

  1. Energy of affinity
  2. Bond energy
  3. Crystal energy
  4. Potential energy
Show answer

Correct answer: (c) Crystal energy

Lattice energy is also called crystal energy.

93.Born-Haber cycle is used to determine the lattice energies of: (PMC MDCAT 2020)

  1. Molecular solids
  2. Metallic solids
  3. Ionic solids
  4. Covalent solids
Show answer

Correct answer: (c) Ionic solids

The Born-Haber cycle gives the lattice energy of an ionic crystal, which cannot be measured directly.

94.At equilibrium the concentrations of the reactants and the products become: (MDCAT 2020)

  1. zero
  2. equal
  3. constant
  4. infinite
Show answer

Correct answer: (c) constant

The two opposing rates are equal, so the concentrations stop changing, though they need not be equal to each other.

95.For a gaseous phase reaction, when number of moles of reactants and products are equal: (PMC MDCAT 2020)

  1. The values of Kp and Kc are different
  2. The value of Kp is greater than Kc
  3. The value of Kc is greater than Kp
  4. The values of Kp and Kc are the same
Show answer

Correct answer: (d) The values of Kp and Kc are the same

$K_p=K_c(RT)^{\Delta n}$, and with $\Delta n$ zero the two are equal.

96.Which of the following reaction has greater Kp than Kc? (PMC MDCAT 2020)

  1. 2NO + Cl2 2NOCl
  2. 2SO2 + O2 2SO3
  3. 2NOCl 2NO + Cl2
  4. N2 + 3H2 2NH3
Show answer

Correct answer: (c) 2NOCl 2NO + Cl2

$K_p=K_c(RT)^{\Delta n}$, and only that reaction goes from two molecules to three.

97.For a gaseous reaction, an increase in pressure will shift the equilibrium in the direction of: (MDCAT 2020)

  1. decreased concentration
  2. increased concentration
  3. decreased volume
  4. increased volume
Show answer

Correct answer: (c) decreased volume

The system relieves the pressure by moving to the side with fewer gas molecules, which occupies less volume.

98.In the reaction $\mathrm{H_2+CO_2\rightleftharpoons H_2O+CO}$, a decrease in the concentration of $\mathrm{CO_2}$ will shift the equilibrium: (MDCAT 2020)

  1. towards the left
  2. towards the right
  3. nothing happens to the equilibrium
  4. towards both directions
Show answer

Correct answer: (a) towards the left

Taking a reactant away makes the reverse reaction the faster of the two, so the equilibrium moves back to the left.

99.When the numbers of moles of reactants and products are equal in a reversible gaseous reaction, which parameter would not affect the equilibrium? (MDCAT 2020)

  1. temperature
  2. pressure
  3. concentration
  4. catalyst
Show answer

Correct answer: (b) pressure

With no change in the number of gas molecules there is no volume change for the pressure to act on.

100.Purification of table salt (NaCl) by passing HCl gas through its saturated aqueous solution is an example of: (PMC MDCAT 2020)

  1. Law of mass action
  2. Hess’s law
  3. Common ion effect
  4. Henry’s law
Show answer

Correct answer: (c) Common ion effect

The added chloride is the ion common to the salt, so the sodium chloride is driven out of solution.

101.A buffer solution is not formed by: (MDCAT 2020)

  1. $\mathrm{NH_4OH+NH_4Cl}$
  2. $\mathrm{CH_3COOH+CH_3COONa}$
  3. $\mathrm{C_2H_5COOH+C_2H_5COONa}$
  4. $\mathrm{HCl+NaCl}$
Show answer

Correct answer: (d) $\mathrm{HCl+NaCl}$

A buffer needs a weak acid or base with its own salt; HCl is a strong acid, so this mixture has no reserve to soak up added acid or alkali.

102.The equation N2(g)+ 3H2(g)⇋ 2NH3(g)represents: (PMC MDCAT 2020)

  1. Contact process
  2. Haber’s process
  3. Solvay process
  4. Avogadro’s Law
Show answer

Correct answer: (b) Haber’s process

That is the Haber process for ammonia.

103.The rate of a reaction: (MDCAT 2020)

  1. increases as the reaction proceeds
  2. decreases as the reaction proceeds
  3. remains the same
  4. may decrease or increase
Show answer

Correct answer: (b) decreases as the reaction proceeds

The reactants are being used up, so their concentrations and with them the rate fall as the reaction goes on.

104.The study of rates of chemical reactions and the factors that affect the rates of chemical reactions is known as: (PMC MDCAT 2020)

  1. Thermodynamics
  2. Stoichiometry
  3. Electrochemistry
  4. Chemical Kinetics
Show answer

Correct answer: (d) Chemical Kinetics

That study is chemical kinetics.

105.In a reversible reaction, a catalyst lowers the activation energy of the: (MDCAT 2020)

  1. forward reaction
  2. reverse reaction
  3. forward as well as the reverse reaction
  4. forward reaction but raises that of the reverse reaction
Show answer

Correct answer: (c) forward as well as the reverse reaction

The catalyst offers a lower path between the same two states, so both directions are speeded up equally and the equilibrium is unmoved.

106.For which of the following order of the reaction, rate of reaction is inversely proportional to the concentration reaction? (PMC MDCAT 2020)

  1. 1st order reaction
  2. 2nd order reaction
  3. Negative order of reaction
  4. Zero order of reaction
Show answer

Correct answer: (c) Negative order of reaction

A rate falling as the concentration rises means the order in that reactant is negative.

107.The effect of temperature on the rate of a reaction is given by: (MDCAT 2020)

  1. Henderson's equation
  2. the general gas equation
  3. the Arrhenius equation
  4. the van der Waals equation
Show answer

Correct answer: (c) the Arrhenius equation

$k=Ae^{-E_a/RT}$ is the Arrhenius equation.

108.The unit of the rate constant is the same as that of the rate of reaction in: (PMC MDCAT 2020)

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

Correct answer: (a) Zero order reaction

For a zero order reaction the rate equals $k$.

109.The thermal energy at constant pressure is called: (PMC MDCAT 2020)

  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.

110.During oxidation process, oxidation number of an element: (PMC MDCAT 2020)

  1. Decreases
  2. Increases
  3. Remains constant
  4. Both decreases and increases
Show answer

Correct answer: (b) Increases

Oxidation is loss of electrons, which raises the oxidation number.

111.The oxidation state of “S’ in the (S2O3)-2 is: (PMC MDCAT 2020)

  1. +4
  2. +6
  3. -2
  4. +2
Show answer

Correct answer: (d) +2

Three oxygens at $-2$ and a charge of $-2$ leave $+4$ for two sulphur atoms, that is $+2$ each.

112.The common oxidation number of halogens is: (PMC MDCAT 2020)

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

Correct answer: (a) -1

A halogen needs one electron to complete its octet, so it is usually $-1$.

113.The stronger the oxidizing agent, the greater is its: (MDCAT 2020)

  1. oxidation potential
  2. reduction potential
  3. redox potential
  4. emf
Show answer

Correct answer: (b) reduction potential

An oxidizing agent is itself reduced, so the more readily it takes electrons the higher its standard reduction potential.

114.Which of the following hybrid orbitals has maximum “s” character? (PMC MDCAT 2020)

  1. Sp3 hybrid orbital
  2. Sp2 hybrid orbital
  3. Sp hybrid orbital
  4. Dsp2 hybrid orbital
Show answer

Correct answer: (c) Sp hybrid orbital

An sp orbital is half s character, more than sp2 or sp3.

115.Which of the following halogen molecules has the maximum bond energy? (MDCAT 2020)

  1. $\mathrm{F_2}$
  2. $\mathrm{Cl_2}$
  3. $\mathrm{Br_2}$
  4. $\mathrm{I_2}$
Show answer

Correct answer: (b) $\mathrm{Cl_2}$

Chlorine is the strongest of the halogen bonds; in $\mathrm{F_2}$ the two small atoms' lone pairs repel and weaken it.

116.Which of the following has the highest value of electronegativity? (PMC MDCAT 2020)

  1. I
  2. Br
  3. Cl
  4. F
Show answer

Correct answer: (d) F

Fluorine is the most electronegative element.

117.Densities of alkali metals are low due to: (PMC MDCAT 2020)

  1. Weak intermolecular forces
  2. Large atomic volume
  3. Smaller size
  4. Ns1 configuration
Show answer

Correct answer: (b) Large atomic volume

The atoms are large and loosely packed, so a given mass takes up a great deal of room.

118.The first ionization energy is maximum for: (PMC MDCAT 2020)

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

Correct answer: (b) Mg

Magnesium has a filled 3s subshell, which makes its first electron harder to remove than aluminium’s.

119.Potassium, Rubidium, Cesium react with oxygen to form which types of oxides? (PMC MDCAT 2020)

  1. Peroxide
  2. Superoxide
  3. Suboxide
  4. Normal oxide
Show answer

Correct answer: (b) Superoxide

The larger alkali metals burn to superoxides; sodium gives a peroxide and lithium the simple oxide.

120.Magnesium reacts with nitrogen to form: (PMC MDCAT 2020)

  1. Mg2N2
  2. Mg3N2
  3. MgN2
  4. MgN
Show answer

Correct answer: (b) Mg3N2

Magnesium burns in nitrogen to $\mathrm{Mg_3N_2}$.

121.The transition element which does not show variable valency is: (PMC MDCAT 2020)

  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.

122.In 3rd series of transition elements, paramagnetic behaviour is maximum for Mn +2 and : (PMC MDCAT 2020)

  1. Cr3+
  2. Ti3+
  3. V3+
  4. Zn2+
Show answer

Correct answer: (a) Cr3+

Chromium(III) and manganese(II) both have half filled or nearly half filled d subshells with the most unpaired electrons.

123.Select the organic compound which belongs to Arene family: (PMC MDCAT 2020)

  1. CH2 = CH2
  2. CH3 – O – CH3
  3. CH3 – NH2
  4. C6H6
Show answer

Correct answer: (d) C6H6

Benzene is the parent of the arenes.

124.IUPAC name of C6H5 – CH2 – CH2 – NH2 is: (PMC MDCAT 2020)

  1. 2-phenyl ethenamine
  2. 2-phenyl ethanamine
  3. 2-phenyl ethylamine
  4. 3-phenyl ethanamine
Show answer

Correct answer: (b) 2-phenyl ethanamine

The chain is ethane with an amino group on carbon 1 and a phenyl group on carbon 2.

125.The type of isomerism existing in a compound of molecular formula C2H6O is: (PMC MDCAT 2020)

  1. Functional group
  2. Position
  3. Chain
  4. Metamerism
Show answer

Correct answer: (a) Functional group

Ethanol and dimethyl ether share the formula but carry different functional groups.

126.Electrophile in sulphonation of benzene is: (PMC MDCAT 2020)

  1. HSO4-
  2. H2SO4
  3. SO3
  4. HSO3
Show answer

Correct answer: (c) SO3

Sulphur trioxide is electron poor at sulphur and attacks the ring directly.

127.Acetophenone can be formed by which of the following reaction for benzene? (PMC MDCAT 2020)

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

Correct answer: (b) Acylation

Friedel-Crafts acylation with acetyl chloride gives acetophenone.

128.When CH3 is attached to the benzene ring, it makes the ring a: (PMC MDCAT 2020)

  1. Good electrophile
  2. Good nucleophile
  3. Resonance hybrid
  4. Extraordinary stable
Show answer

Correct answer: (b) Good nucleophile

The methyl group feeds electrons into the ring, so the ring becomes richer in electrons and attacks electrophiles.

129.R-X on reaction with alcohols form: (PMC MDCAT 2020)

  1. R-OH
  2. ROR
  3. R-X-OH
  4. RH
Show answer

Correct answer: (b) ROR

The alkoxide displaces the halide and an ether is left, which is Williamson’s synthesis.

130.Alkyl halides involving -C-X bond breakage and -C-Nu bond formation simultaneously would follow the mechanism: (PMC MDCAT 2020)

  1. SN1
  2. SN2
  3. E1
  4. E2
Show answer

Correct answer: (b) SN2

In an SN2 reaction the nucleophile comes in as the halide goes out, in one step.

131.Phenol is more acidic than alcohols because of the following reason: (PMC MDCAT 2020)

  1. Delocalization of negative charge in OH group
  2. Delocation of positive charge on the carbon atom in ring
  3. Delocalization of negative charge in the ring
  4. Delocalization of positive charge in the OH group
Show answer

Correct answer: (c) Delocalization of negative charge in the ring

The ring spreads the negative charge of the phenoxide ion, which an alkoxide cannot do.

132.Phenol is known as: (PMC MDCAT 2020)

  1. Carpolic acid
  2. Carbonylic acid
  3. Carbolic acid
  4. Carbolylic acid
Show answer

Correct answer: (c) Carbolic acid

Phenol is known as carbolic acid.

133.Which of the following reagent is used to separate and purify carbonyl and non carbonyl compounds? (PMC MDCAT 2020)

  1. HCN
  2. BrMgCH3
  3. NaHSO3
  4. H2O
Show answer

Correct answer: (c) NaHSO3

Sodium bisulphite gives a crystalline addition product with aldehydes and methyl ketones, which is then hydrolysed back.

134.The hydrolysis of nitriles produces: (MDCAT 2020)

  1. carboxylic acids
  2. aldehydes
  3. ketones
  4. esters
Show answer

Correct answer: (a) carboxylic acids

$\mathrm{RCN+2H_2O\to RCOOH+NH_3}$, which is one of the standard preparations of an acid.

135.The exact reactivity order for carboxylic acid derivatives is: (PMC MDCAT 2020)

  1. Anhydride > Acylchloride > ester
  2. Ester > Anhydride > Acylchloride
  3. Amide > Acylchloride > ester
  4. Acylchloride > Anhydride > ester
Show answer

Correct answer: (d) Acylchloride > Anhydride > ester

The better the leaving group, the more reactive the derivative, and chloride leaves most readily.

136.Which of the following is the strongest acid? (PMC MDCAT 2020)

  1. Propanoic acid
  2. Fluoroethanoic acid
  3. Trichloroethanoic acid
  4. Nitroethanoic acid
Show answer

Correct answer: (c) Trichloroethanoic acid

Three chlorine atoms pull hardest on the carboxyl group, so its proton is the most readily lost.

137.Acetic anhydride is a product of acetic acid as a result of which reaction? (MDCAT 2020)

  1. dehydration
  2. reduction
  3. oxidation
  4. esterification
Show answer

Correct answer: (a) dehydration

Two molecules of the acid lose one molecule of water between them.

138.Hydrolysis of acyl chloride results in the formation of: (PMC MDCAT 2020)

  1. Acid anhydride
  2. Carboxylic acid
  3. Amides
  4. Esters
Show answer

Correct answer: (b) Carboxylic acid

Water attacks the acyl chloride and leaves the carboxylic acid and hydrogen chloride.

139.Based on the physico-chemical properties, proteins may be classified into the following types: (PMC MDCAT 2020)

  1. Simple proteins
  2. Compound proteins
  3. Derived proteins
  4. All of the above
Show answer

Correct answer: (d) All of the above

Proteins are classed as simple, compound or derived.

140.Based on function, thyroxine can be classified as: (PMC MDCAT 2020)

  1. Hormonal protein
  2. Structural protein
  3. Transport protein
  4. Genetic protein
Show answer

Correct answer: (a) Hormonal protein

Thyroxine carries a message from a gland to its target, so it is classed as a hormonal protein.

141.Which of the following enzymes is raised in rickets? (MDCAT 2020)

  1. lactic dehydrogenase
  2. alkaline phosphatase
  3. amylase
  4. lipase
Show answer

Correct answer: (b) alkaline phosphatase

Bone turnover is high in rickets, and the osteoblasts release alkaline phosphatase into the blood.

142.L – Asparaginase enzyme has been used for the treatment of: (PMC MDCAT 2020)

  1. Jaundice
  2. Blood cancer
  3. Rickets
  4. Heart disease
Show answer

Correct answer: (b) Blood cancer

L-asparaginase starves leukaemic cells of asparagine and is used against blood cancer.

Physics

143.Under what condition an object will have zero displacement but non zero distance? (PMC MDCAT 2020)

  1. Linear motion
  2. Circular motion
  3. Random motion
  4. Oscillation
Show answer

Correct answer: (b) Circular motion

A complete circle brings the body back to its start, so the displacement is zero but the path is not.

144.The slope of distance – time graph will always be: (PMC MDCAT 2020)

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

Correct answer: (b) Positive

Distance can only grow, so the slope is never below zero.

145.If we drop an object, it’s initial velocity is zero. How far will it fall in time ‘t’? (PMC MDCAT 2020)

  1. 9.8 t2
  2. 4.9 t2
  3. 0.49 t2
  4. 98 t2
Show answer

Correct answer: (b) 4.9 t2

$s=\tfrac12gt^2$, and half of $9.8$ is $4.9$.

146.At what angle of projection of a projectile the range becomes half of its maximum value? (PMC MDCAT 2020)

  1. 15
  2. 20
  3. 30
  4. 40
Show answer

Correct answer: (a) 15

Half the maximum range needs $\sin2\theta=0.5$, so $\theta$ is $15^{\circ}$.

147.The product of force and time is equal to: (MDCAT 2020)

  1. angular momentum
  2. force
  3. change in momentum
  4. velocity
Show answer

Correct answer: (c) change in momentum

$F\Delta t$ is the impulse, and the impulse equals the change in momentum.

148.The time rate of change of linear momentum of a body is equal to its: (MDCAT 2020)

  1. force
  2. momentum
  3. power
  4. acceleration
Show answer

Correct answer: (a) force

Newton's second law in its general form is $F=\Delta p/\Delta t$.

149.The newton-second is the unit of: (PMC MDCAT 2020)

  1. Work
  2. Power
  3. Impulse
  4. Momentum
Show answer

Correct answer: (c) Impulse

Force times time is impulse, measured in newton seconds.

150.A 10 N force moves a body around a circular path of radius 50 cm. What is the work done in completing one revolution? (MDCAT 2020)

  1. 25 J
  2. zero
  3. 31.42 J
  4. 500 J
Show answer

Correct answer: (b) zero

The body returns to its starting point, so the displacement is zero and so is the work.

151.The area under a force-displacement graph gives us the: (MDCAT 2020)

  1. displacement
  2. power
  3. work
  4. acceleration
Show answer

Correct answer: (c) work

Force multiplied by displacement is work, and that product is the area under the graph.

152.A 1.75 m tall weight-lifter raises a weight of mass 50 kg to a height of 0.5 m above its head. How much work is being done by it? (g = 10 ms-2) (PMC MDCAT 2020)

  1. 2125 J
  2. 2500 J
  3. 50 J
  4. 1125 J
Show answer

Correct answer: (d) 1125 J

The weight is lifted from the ground to $1.75+0.5\,\mathrm{m}$, so $W=50\times10\times2.25$, that is $1125\,\mathrm{J}$.

153.When the speed of your car is halved, by what factor does its kinetic energy decreases? (PMC MDCAT 2020)

  1. ½
  2. ¼
  3. ⅛
  4. ⅙
Show answer

Correct answer: (b) ¼

$K$ goes as the square of the speed, so half the speed leaves a quarter of the energy.

154.A 3 kg stone falls from a 20 m high platform. Find its speed at a height of 10 m. (MDCAT 2020)

  1. $190\ \mathrm{m\,s^{-1}}$
  2. $14\ \mathrm{m\,s^{-1}}$
  3. $10\ \mathrm{m\,s^{-1}}$
  4. $100\ \mathrm{m\,s^{-1}}$
Show answer

Correct answer: (b) $14\ \mathrm{m\,s^{-1}}$

It has fallen 10 m, so $v=\sqrt{2gh}=\sqrt{2(10)(10)}\approx14\ \mathrm{m\,s^{-1}}$.

155.What is the speed of 2.0 kg metallic bob at the mean position of a simple pendulum, when released from its extreme position 0.5m high? (g = 10 ms-2) (PMC MDCAT 2020)

  1. 3.16 ms-1
  2. 10 ms-1
  3. 100 ms-1
  4. 50 ms -1
Show answer

Correct answer: (a) 3.16 ms-1

$v=\sqrt{2gh}=\sqrt{2\times10\times0.5}$, that is $3.16\,\mathrm{m\,s^{-1}}$.

156.Which one of the following force is non-conservative: (PMC MDCAT 2020)

  1. Frictional force
  2. Gravitational force
  3. Electric force
  4. Elastic spring force
Show answer

Correct answer: (a) Frictional force

The work done against friction depends on the path taken, so friction is not conservative.

157.The kilowatt-hour is a unit of: (MDCAT 2020)

  1. electric energy
  2. power
  3. momentum
  4. intensity
Show answer

Correct answer: (a) electric energy

It is a power multiplied by a time, so it measures energy.

158.One kilowatt-hour is equal to: (MDCAT 2020)

  1. $1.6\times10^{6}\ \mathrm{J}$
  2. $3.6\times10^{6}\ \mathrm{J}$
  3. $9.1\times10^{6}\ \mathrm{J}$
  4. $1.6\times10^{-19}\ \mathrm{J}$
Show answer

Correct answer: (b) $3.6\times10^{6}\ \mathrm{J}$

$1000\ \mathrm{W}\times3600\ \mathrm{s}=3.6\times10^{6}$ J.

159.One kilowatt-hour is commonly termed as one commercial unit of electric energy which is equal to: (PMC MDCAT 2020)

  1. 3.6 x 105 J
  2. 3.6 x 106 J
  3. 3.6 x 104 J
  4. 3.6 x 103 J
Show answer

Correct answer: (b) 3.6 x 106 J

A kilowatt for an hour is $1000\times3600$, that is $3.6\times10^6\,\mathrm{J}$.

160.1 radian is equal to: (PMC MDCAT 2020)

  1. 57.1 degrees
  2. 57.2 degrees
  3. 57.3 degrees
  4. 57.4 degrees
Show answer

Correct answer: (c) 57.3 degrees

One radian is $180/\pi$ degrees, about $57.3^{\circ}$.

161.The earth rotates on its axis once a day. Suppose, by some process the earth contracts so that it’s radius is only half as large as at present, then how long the earth will take to complete it’s rotation? (PMC MDCAT 2020)

  1. 24 hours
  2. 18 hours
  3. 6 hours
  4. 12 hours
Show answer

Correct answer: (c) 6 hours

Angular momentum is conserved and $I$ goes as $r^2$, so a half radius spins four times as fast, in six hours.

162.If during circular motion, tangential velocity of a body becomes double, then centripetal force becomes: (PMC MDCAT 2020)

  1. Double
  2. One half
  3. Four times
  4. One fourth
Show answer

Correct answer: (c) Four times

$F=mv^2/r$ goes as the square of the speed.

163.In a ripple tank 40 waves pass through a certain point in one second. If the wavelength of the waves is 5 cm, then find the speed of the wave. (MDCAT 2020)

  1. $2\ \mathrm{m\,s^{-1}}$
  2. $8\ \mathrm{m\,s^{-1}}$
  3. $20\ \mathrm{m\,s^{-1}}$
  4. $200\ \mathrm{m\,s^{-1}}$
Show answer

Correct answer: (a) $2\ \mathrm{m\,s^{-1}}$

$v=f\lambda=40\times0.05=2\ \mathrm{m\,s^{-1}}$.

164.The product of frequency and time period is equal to: (MDCAT 2020)

  1. 1
  2. 2
  3. 0
  4. $1/2$
Show answer

Correct answer: (a) 1

$T=1/f$, so $fT=1$.

165.In a ripple tank, 40 waves pass through a certain point in 1 second. If the wavelength of the wave is 5 cm, then speed of the wave is: (PMC MDCAT 2020)

  1. 0.5 ms-1
  2. 1 ms-1
  3. 1.5 ms-1
  4. 2 ms-1
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Correct answer: (d) 2 ms-1

$v=f\lambda=40\times0.05$, that is $2\,\mathrm{m\,s^{-1}}$.

166.Which one of the following properties is not exhibited by the longitudinal waves? (PMC MDCAT 2020)

  1. Interference
  2. Reflection
  3. Diffraction
  4. Polarization
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Correct answer: (d) Polarization

Polarization needs a vibration across the direction of travel, which a longitudinal wave has not.

167.The speed of sound in air is 332 m/s. The speed of sound at 22 degrees centigrade will be: (PMC MDCAT 2020)

  1. 345.2 m/s
  2. 340 m/s
  3. 350 m/s
  4. 330 m/s
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Correct answer: (a) 345.2 m/s

$332+0.61\times22$ gives about $345\,\mathrm{m\,s^{-1}}$.

168.The rapid escape of air from a burst tyre is an example of a process that is: (MDCAT 2020)

  1. isothermal
  2. adiabatic
  3. isobaric
  4. isochoric
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Correct answer: (b) adiabatic

The escape is too quick for any heat exchange, so $Q=0$ and the air cools as it does work.

169.In which process the entire heat supplied to the gas is converted to the internal energy of the gas? (PMC MDCAT 2020)

  1. Isochoric process
  2. Isobaric process
  3. Isothermal process
  4. Adiabatic process
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Correct answer: (a) Isochoric process

At constant volume no work is done, so all the heat goes into the internal energy.

170.If we double the separation between two charges, then Coulomb's force will become: (MDCAT 2020)

  1. doubled
  2. half
  3. four times
  4. one fourth
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Correct answer: (d) one fourth

$F\propto1/r^2$, so twice the separation leaves a quarter of the force.

171.The values of electric intensity will ____ due to the presence of dielectric medium: (PMC MDCAT 2020)

  1. Increase
  2. Increase exponentially
  3. Decrease
  4. Remain same
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Correct answer: (c) Decrease

The medium divides the field by its relative permittivity.

172.If the potential at a point which is 1m from a charge is 1 volt, then the potential at a point which is 2m from the same charge will be: (PMC MDCAT 2020)

  1. 2 V
  2. 1 V
  3. 0.5 V
  4. 3 V
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Correct answer: (c) 0.5 V

The potential of a point charge goes as $1/r$, so twice the distance halves it.

173.By increasing the area of the plates and decreasing the distance between them, the capacitance of a capacitor: (MDCAT 2020)

  1. increases
  2. decreases
  3. remains unchanged
  4. depends only upon temperature
Show answer

Correct answer: (a) increases

$C=\varepsilon_0A/d$ rises with the area and falls with the separation.

174.Ohm multiplied by farad is equivalent to: (PMC MDCAT 2020)

  1. Time
  2. Charge
  3. Distance
  4. Capacitor
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Correct answer: (a) Time

Ohms times farads give seconds, which is why $RC$ is a time constant.

175.In what form is the energy stored in a charged capacitor? (PMC MDCAT 2020)

  1. gravitational
  2. electrical potential
  3. magnetic field
  4. potential
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Correct answer: (b) electrical potential

The work done in charging it is stored as electrical potential energy in the field between the plates.

176.One of the following is an Ohmic device: (PMC MDCAT 2020)

  1. Filament bulb
  2. Semiconductor diode
  3. Transistor
  4. Copper wire
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Correct answer: (d) Copper wire

A copper wire at constant temperature obeys Ohm’s law; the other three do not.

177.The unit of resistivity is the: (MDCAT 2020)

  1. ohm
  2. ohm metre
  3. ohm per metre
  4. metre per ohm
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Correct answer: (b) ohm metre

From $\rho=RA/L$ the unit is the ohm metre.

178.When a wire is compressed and it’s radius becomes 2R then it’s resistance will be: (PMC MDCAT 2020)

  1. 16R
  2. 4 R
  3. 1 / 16 R
  4. 1 / 4 R
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Correct answer: (c) 1 / 16 R

The volume is fixed, so four times the area means a quarter of the length, and $R$ falls to a sixteenth.

179.The change in resistance of metallic conductor at temperature below 0 degrees is: (PMC MDCAT 2020)

  1. Non-linear
  2. Curve
  3. Linear
  4. Curvilinear
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Correct answer: (c) Linear

Away from very low temperatures the resistance of a metal rises in a straight line with temperature.

180.The terminal voltage $V_t$ of a battery is greater than the emf of the battery when the: (MDCAT 2020)

  1. battery is charging
  2. battery is discharging
  3. battery is connected with a resistance
  4. battery is connected with a voltmeter
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Correct answer: (a) battery is charging

While charging, the current is driven into the battery, so $V_t=\varepsilon+Ir$ is above the emf.

181.Two parallel straight conductors, in which current is flowing in the same direction, attract each other. The cause of it is: (PMC MDCAT 2020)

  1. magnetic force between the two
  2. electric force between the two
  3. potential difference between the two
  4. mutual induction between the two
Show answer

Correct answer: (a) magnetic force between the two

Each current sits in the magnetic field of the other, and parallel currents are drawn together.

182.When current are flowing through two long parallel wires in same direction electric field between them is: (PMC MDCAT 2020)

  1. Strong
  2. Weak
  3. Remains constant
  4. Infinite
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Correct answer: (c) Remains constant

The wires carry no net charge, so the electric field between them does not change; it is the magnetic force that draws them together.

183.Magnetic flux is maximum when angle between magnetic field and vector area is: (PMC MDCAT 2020)

  1. 0
  2. 90
  3. 180
  4. 45
Show answer

Correct answer: (a) 0

$\Phi=BA\cos\theta$ is greatest when the area vector lies along the field.

184.If a stationary bar magnet is placed near a coil so that maximum lines of force passes through the coil, the galvanometer shows: (PMC MDCAT 2020)

  1. Maximum current
  2. Minimum current
  3. No current
  4. Intermediate value of current
Show answer

Correct answer: (c) No current

An emf appears only while the flux is changing, and a stationary magnet changes nothing.

185.Transformer is a device which steps up or steps down the input: (PMC MDCAT 2020)

  1. Current
  2. Voltage
  3. Energy
  4. Power
Show answer

Correct answer: (b) Voltage

A transformer changes the voltage; the power stays much the same.

186.In transmission from grid station, power losses are minimized by: (PMC MDCAT 2020)

  1. Increasing current
  2. Decreasing current
  3. Increasing resistance
  4. Increasing voltage
Show answer

Correct answer: (d) Increasing voltage

The loss is $I^2R$, so the voltage is stepped up and the current down for transmission.

187.The domestic electricity supply has a frequency of: (PMC MDCAT 2020)

  1. 150 Hz
  2. 100 Hz
  3. 50 Hz
  4. 25 Hz
Show answer

Correct answer: (c) 50 Hz

Mains electricity in Pakistan is supplied at $50\,\mathrm{Hz}$.

188.In a full-wave rectification, the number of diodes used are: (PMC MDCAT 2020)

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

Correct answer: (d) 4

A bridge rectifier uses four diodes.

189.PIV stands for : (PMC MDCAT 2020)

  1. Positive inverse voltage
  2. Pawn Bh Integrated voltage
  3. Peak inverse voltage
  4. Peak integrated voltage
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Correct answer: (c) Peak inverse voltage

PIV is the peak inverse voltage a diode must stand when it is not conducting.

190.The wavelength associated with an electron is of the order of: (PMC MDCAT 2020)

  1. Visible light
  2. X rays
  3. Radio waves
  4. Infrared
Show answer

Correct answer: (b) X rays

An accelerated electron has a wavelength of about an ångström, the wavelength of X-rays.

191.Which photon carries the most energy? (PMC MDCAT 2020)

  1. Blue
  2. Violet
  3. Red
  4. Green
Show answer

Correct answer: (b) Violet

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

192.Which of the following series lies in the ultraviolet range: (PMC MDCAT 2020)

  1. Balmer series
  2. Pashcher series
  3. Lyman series
  4. Brackett series
Show answer

Correct answer: (c) Lyman series

The Lyman lines end on the ground level and lie in the ultraviolet.

193.The main difference between X rays and Y rays is: (PMC MDCAT 2020)

  1. Frequency
  2. Wave length
  3. Energy
  4. Origin
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Correct answer: (d) Origin

X-rays come from the electron cloud and gamma rays from the nucleus; their wavelengths overlap.

194.There are initially 400 atoms in a radioactive sample. What would be the number of atoms after 3 half – life? (PMC MDCAT 2020)

  1. 400
  2. 200
  3. 50
  4. 25
Show answer

Correct answer: (c) 50

Three half lives leave an eighth, and $400/8$ is $50$.

195.While using radiation therapy, cancerous thyroid is treated with ____ radioisotope: (PMC MDCAT 2020)

  1. Carbon
  2. 235 Uranium
  3. Thorium
  4. Iodine
Show answer

Correct answer: (d) Iodine

Iodine-131 gathers in the thyroid, so it is used to treat thyroid cancer.

English

196.‘She always carried an umbrella’. The sentence indicates ____ tense. (PMC MDCAT 2020)

  1. Present Simple
  2. Past Simple
  3. Past Perfect
  4. Present Perfect
Show answer

Correct answer: (b) Past Simple

Carried is the simple past.

197.We prefer fruits ____ sweets. (PMC MDCAT 2020)

  1. Then
  2. On
  3. Over
  4. From
Show answer

Correct answer: (c) Over

Prefer takes to or over, not than.

198.Choose the correctly punctuated sentence: (PMC MDCAT 2020)

  1. What a fall was there, my country men! Long live the king!
  2. What a fall was there! My countrymen. Long live the king!
  3. What a fall was there, my countrymen. Long live the king.
  4. What a fall was there, my countrymen, long live the King.
Show answer

Correct answer: (a) What a fall was there, my country men! Long live the king!

The exclamation is closed with an exclamation mark and the address is set off by a comma.

199.Not only the parents but also their son ______ for interview. (PMC MDCAT 2020)

  1. Has called
  2. Have called
  3. Have been called
  4. Has been called
Show answer

Correct answer: (d) Has been called

With not only but also the verb agrees with the nearer subject, son, which is singular and passive here.

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