Chemistry carries 25% of the total MDCAT marks with 45 MCQs, making it the second most important subject after Biology. Many students find Chemistry challenging because it spans 20 chapters across Physical, Inorganic, and Organic Chemistry. However, the PMC has a clear pattern of repeating core concepts year after year.
We have analysed every MDCAT paper from 2008 to 2025 and compiled the 30 most frequently repeated Chemistry MCQs. These questions target the exact concepts that PMC examiners return to again and again. If you can answer all 30 correctly, you are already well on your way to scoring 35+ out of 45 in Chemistry.
The questions below are drawn from the Punjab FSc Chemistry textbooks (Part-I and Part-II) published by the Punjab Textbook Board, which remain the primary source for PMC MDCAT Chemistry. We have grouped them by chapter so you can see which areas deserve the most revision time.
MDCAT Chemistry at a Glance: 45 MCQs | 25% weightage | 20 chapters from FSc Part-I & Part-II | A mix of numerical problems, conceptual recall, and reaction-based questions. Organic Chemistry alone accounts for roughly 30-35% of the Chemistry paper.
Chapter-wise Frequency Analysis
Not all 20 chapters carry equal weight. Some chapters consistently produce more MCQs than others. Here is the approximate distribution based on past paper analysis:
| Chapter | Approx. MCQs per Paper | Frequency |
|---|---|---|
| Atomic Structure | 3-4 | Very High |
| Chemical Bonding | 3-4 | Very High |
| Chemical Equilibrium | 2-3 | High |
| Electrochemistry | 2-3 | High |
| Reaction Kinetics | 2-3 | High |
| Thermo-Chemistry and Energetics | 2-3 | High |
| Gases | 2-3 | High |
| S and P Block Elements | 2-3 | High |
| Transition Elements | 1-2 | Medium |
| Fundamental Principles of Organic Chemistry | 2-3 | High |
| Chemistry of Hydrocarbons | 2-3 | Very High |
| Alkyl Halides | 1-2 | Medium |
| Alcohols and Phenols | 2-3 | High |
| Aldehydes and Ketones | 2-3 | High |
| Carboxylic Acids | 1-2 | Medium |
| Macromolecules | 1-2 | Medium |
| Introduction to Fundamental Concepts | 1-2 | Medium |
| Liquids | 1-2 | Medium |
| Solids | 1-2 | Medium |
| Industrial Chemistry | 1-2 | Medium |
As you can see, Atomic Structure, Chemical Bonding, and Organic Chemistry chapters (Hydrocarbons through Carboxylic Acids) dominate the paper. A smart student will master these high-yield chapters first before moving to lower-frequency topics.
Atomic Structure
Chapter: Atomic Structure
Question 1
The maximum number of electrons in a sub-shell is given by the formula:
Explanation: The maximum number of electrons in a sub-shell is 2(2l + 1), where l is the azimuthal quantum number. For example, for the p sub-shell (l = 1), maximum electrons = 2(2 x 1 + 1) = 6. The formula 2n² gives the maximum electrons in a complete shell, not a sub-shell.
Chapter: Atomic Structure
Question 2
Which of the following sets of quantum numbers is NOT allowed?
Explanation: The azimuthal quantum number l can have values from 0 to (n - 1). For n = 2, the maximum value of l is 1 (not 2). Therefore, n=2, l=2 is an impossible combination, making option C the correct answer.
Chapter: Atomic Structure
Question 3
The emission spectrum of hydrogen in the visible region is called:
Explanation: The Balmer series corresponds to electronic transitions to n = 2 and falls in the visible region of the electromagnetic spectrum. The Lyman series (transitions to n = 1) is in the UV region, while Paschen (n = 3), Brackett (n = 4) and Pfund (n = 5) series are in the infrared region.
Chemical Bonding
Chapter: Chemical Bonding
Question 4
The bond angle in a molecule with sp³ hybridization is:
Explanation: sp³ hybridization results in a tetrahedral geometry with bond angles of 109.5°. Examples include CH4 and CCl4. sp² hybridization gives 120° (trigonal planar), and sp hybridization gives 180° (linear).
Chapter: Chemical Bonding
Question 5
Which of the following molecules has the highest dipole moment?
Explanation: HF has a high dipole moment (1.91 D) because fluorine is the most electronegative element, creating a strong polar bond. CO2, BF3, and CCl4 are all symmetrical molecules where individual bond dipoles cancel out, giving a net dipole moment of zero.
Chapter: Chemical Bonding
Question 6
According to VSEPR theory, the shape of NH3 molecule is:
Explanation: NH3 has three bonding pairs and one lone pair around the central nitrogen atom. The electron geometry is tetrahedral, but the molecular shape is trigonal pyramidal because the lone pair compresses the bond angle from 109.5° to about 107°.
Gases
Chapter: Gases
Question 7
At constant temperature, the product of pressure and volume of a given mass of gas is constant. This statement is known as:
Explanation: Boyle's law states that at constant temperature, the volume of a given mass of gas is inversely proportional to its pressure (PV = constant or P1V1 = P2V2). Charles's law relates volume to temperature at constant pressure.
Chapter: Gases
Question 8
The gas that diffuses fastest at the same temperature and pressure is:
Explanation: According to Graham's law of diffusion, the rate of diffusion is inversely proportional to the square root of the molar mass. H2 has the lowest molar mass (2 g/mol) among the given options, so it diffuses the fastest.
Chemical Equilibrium
Chapter: Chemical Equilibrium
Question 9
A catalyst affects a chemical equilibrium by:
Explanation: A catalyst lowers the activation energy equally for both the forward and reverse reactions, so equilibrium is reached faster but the equilibrium position and the equilibrium constant (Kc) remain unchanged.
Chapter: Chemical Equilibrium
Question 10
The pH of a 0.001 M HCl solution is:
Explanation: HCl is a strong acid that completely dissociates. The H+ concentration equals 0.001 M = 10&sup-3; M. pH = -log[H+] = -log(10&sup-3;) = 3. This is a standard numerical problem that appears almost every year in the MDCAT.
Reaction Kinetics
Chapter: Reaction Kinetics
Question 11
The unit of rate constant for a first order reaction is:
Explanation: For a first order reaction, Rate = k[A]. The unit of rate is mol L&supmin;¹ s&supmin;¹ and [A] is in mol L&supmin;¹. Therefore k = Rate/[A] = (mol L&supmin;¹ s&supmin;¹) / (mol L&supmin;¹) = s&supmin;¹. For a second order reaction, the unit is L mol&supmin;¹ s&supmin;¹.
Chapter: Reaction Kinetics
Question 12
An increase of 10°C in temperature generally increases the rate of reaction by:
Explanation: According to the general rule of thumb, a 10°C rise in temperature approximately doubles or triples the rate of a chemical reaction. This is because more molecules gain enough kinetic energy to cross the activation energy barrier.
Thermo-Chemistry and Energetics
Chapter: Thermo-Chemistry and Energetics
Question 13
For an exothermic reaction, the enthalpy change (ΔH) is:
Explanation: In an exothermic reaction, heat is released to the surroundings. The enthalpy of the products is lower than the enthalpy of the reactants, so ΔH = H(products) - H(reactants) is negative. In endothermic reactions, ΔH is positive.
Chapter: Thermo-Chemistry and Energetics
Question 14
According to Hess's law, the enthalpy change of a reaction:
Explanation: Hess's law states that the total enthalpy change for a reaction is the same regardless of the number of intermediate steps — it depends only on the initial and final states. This is because enthalpy is a state function. A catalyst does not change ΔH.
Electrochemistry
Chapter: Electrochemistry
Question 15
In an electrolytic cell, oxidation takes place at the:
Explanation: In both electrolytic and galvanic cells, oxidation always occurs at the anode and reduction always occurs at the cathode. The difference is that in an electrolytic cell the anode is positive and the cathode is negative, while in a galvanic cell it is the reverse.
Chapter: Electrochemistry
Question 16
The standard electrode potential of Standard Hydrogen Electrode (SHE) is:
Explanation: The Standard Hydrogen Electrode (SHE) is arbitrarily assigned a potential of 0.00 V and serves as the reference electrode against which all other electrode potentials are measured. It consists of a platinum electrode in 1 M H+ solution with H2 gas at 1 atm.
S and P Block Elements
Chapter: S and P Block Elements
Question 17
Which of the following is the strongest oxidizing agent among halogens?
Explanation: Fluorine is the strongest oxidizing agent among all the halogens (and indeed all the elements) because it has the highest electronegativity (4.0) and the highest standard reduction potential (+2.87 V). Oxidizing ability decreases down the group: F2 > Cl2 > Br2 > I2.
Chapter: S and P Block Elements
Question 18
Baking soda has the chemical formula:
Explanation: Baking soda is sodium bicarbonate (NaHCO3), also known as sodium hydrogen carbonate. Na2CO3 is washing soda (sodium carbonate), CaCO3 is limestone/marble, and NaOH is caustic soda.
Transition Elements
Chapter: Transition Elements
Question 19
Transition metals can form coloured compounds because of:
Explanation: Transition metals form coloured compounds due to d-d electronic transitions. When light is absorbed, electrons in the lower-energy d-orbitals are excited to higher-energy d-orbitals. The unabsorbed wavelengths of light are transmitted, producing the characteristic colours. This is only possible when the d sub-shell is partially filled.
Fundamental Principles of Organic Chemistry
Chapter: Fundamental Principles of Organic Chemistry
Question 20
The type of hybridization of carbon in ethene (C2H4) is:
Explanation: In ethene (C2H4), each carbon atom is bonded to two hydrogen atoms and one other carbon via a double bond (one sigma and one pi bond). This requires sp² hybridization, resulting in a trigonal planar geometry with 120° bond angles around each carbon.
Chapter: Fundamental Principles of Organic Chemistry
Question 21
The IUPAC name of CH3-CH(CH3)-CH2-CH3 is:
Explanation: The longest continuous carbon chain has 4 carbons (butane). A methyl group (-CH3) is attached to carbon 2. According to IUPAC rules, we number from the end that gives the lowest locant to the substituent, so the correct name is 2-methylbutane, not 3-methylbutane.
Chemistry of Hydrocarbons
Chapter: Chemistry of Hydrocarbons
Question 22
The addition of HBr to propene in the presence of peroxide follows:
Explanation: In the presence of peroxides, the addition of HBr to an unsymmetrical alkene follows anti-Markovnikov's rule (also called Kharasch effect or peroxide effect). The hydrogen atom adds to the carbon with fewer hydrogen atoms. This effect is observed only with HBr, not with HCl or HI.
Chapter: Chemistry of Hydrocarbons
Question 23
Benzene undergoes which type of reaction predominantly?
Explanation: Benzene predominantly undergoes electrophilic substitution reactions (such as halogenation, nitration, sulphonation, and Friedel-Crafts reactions) rather than addition reactions. This is because substitution preserves the stable aromatic ring system, whereas addition would destroy it.
Alkyl Halides
Chapter: Alkyl Halides
Question 24
SN2 reaction is favoured by:
Explanation: SN2 (bimolecular nucleophilic substitution) is favoured by primary alkyl halides because they have less steric hindrance, allowing the nucleophile easy access to the carbon bearing the leaving group. Tertiary alkyl halides favour SN1 mechanism due to the stability of the tertiary carbocation.
Alcohols and Phenols
Chapter: Alcohols and Phenols
Question 25
Which reagent is used to distinguish between primary, secondary, and tertiary alcohols?
Explanation: Lucas reagent (anhydrous ZnCl2 in concentrated HCl) is used to distinguish between primary, secondary, and tertiary alcohols. Tertiary alcohols react immediately (instant turbidity), secondary alcohols react within 5 minutes, and primary alcohols do not react at room temperature.
Aldehydes and Ketones
Chapter: Aldehydes and Ketones
Question 26
Tollens' test is used to distinguish between:
Explanation: Tollens' test (silver mirror test) uses ammoniacal silver nitrate solution [Ag(NH3)2]+. Aldehydes reduce Ag+ to metallic silver, forming a silver mirror on the test tube wall. Ketones do not give this test because they cannot be easily oxidized.
Chapter: Aldehydes and Ketones
Question 27
The reaction of an aldehyde with HCN to form a cyanohydrin is an example of:
Explanation: The carbonyl group (C=O) in aldehydes and ketones is polar, with the carbon being electrophilic. The CN&supmin; ion acts as a nucleophile and attacks the electrophilic carbon. This is a classic example of nucleophilic addition, which is the characteristic reaction of aldehydes and ketones.
Carboxylic Acids
Chapter: Carboxylic Acids
Question 28
The reaction of a carboxylic acid with an alcohol in the presence of an acid catalyst produces:
Explanation: The reaction of a carboxylic acid with an alcohol in the presence of a mineral acid catalyst (such as H2SO4) is called esterification (Fischer esterification). It produces an ester and water: RCOOH + R'OH ⇄ RCOOR' + H2O. This is a reversible reaction.
Macromolecules
Chapter: Macromolecules
Question 29
Nylon 6,6 is an example of:
Explanation: Nylon 6,6 is a condensation polymer formed by the reaction of hexamethylenediamine (6 carbons) and adipic acid (6 carbons) with the elimination of water molecules. The two numbers (6,6) refer to the number of carbon atoms in each monomer. Addition polymers like polyethylene are formed without the loss of any small molecule.
Industrial Chemistry
Chapter: Industrial Chemistry
Question 30
In the Haber process for manufacturing ammonia, the catalyst used is:
Explanation: The Haber process (N2 + 3H2 ⇄ 2NH3) uses finely divided iron as the catalyst, with small amounts of Al2O3 and K2O as promoters. The reaction is carried out at 450-500°C and 200-300 atm pressure. Vanadium pentoxide (V2O5) is the catalyst used in the Contact process for making sulphuric acid.
Tips for Scoring High in MDCAT Chemistry
Chemistry is often considered the trickiest MDCAT subject because it combines numerical problem-solving with conceptual understanding and reaction memorization. Here are proven strategies from high scorers:
- Master Organic Chemistry reactions. Organic Chemistry (Chapters 13-18) alone makes up about 30-35% of the Chemistry paper. Create reaction maps showing conversions between functional groups: alkanes, alkenes, alkynes, alkyl halides, alcohols, aldehydes, ketones, and carboxylic acids. Know the reagents, conditions, and products for every reaction.
- Memorize the key numerical values. Gas constants (R = 0.0821 L atm mol&supmin;¹ K&supmin;¹ or 8.314 J mol&supmin;¹ K&supmin;¹), standard electrode potentials, ionization energies, and electronegativity values appear in calculations every year. Write them on a flashcard and revise daily.
- Focus on comparison-based questions. PMC loves to test comparisons: bond length vs bond order, acidity of phenol vs ethanol, boiling points of isomers, oxidizing power of halogens. Build comparison tables for each chapter.
- Practise pH and equilibrium calculations. At least 3-4 MCQs involve straightforward calculations: pH, Kc, Kp, molarity, moles, and stoichiometry. These are free marks if you know the formulas and can apply them quickly.
- Understand named reactions and tests. Tollens' test, Fehling's test, Lucas test, Baeyer's test, Friedel-Crafts reaction, Cannizzaro reaction, Aldol condensation, Haber process, Contact process, Solvay process — know what each involves and what it is used for.
- Do not ignore Inorganic Chemistry. S and P Block Elements, Transition Elements, and Industrial Chemistry together contribute 5-7 MCQs. These are mostly factual recall questions and can be scored easily with minimal revision.
- Solve past papers from 2017 onwards. The PMC era papers (2017-2025) are the most relevant. You will notice the same types of questions appearing in different formats. Attempt each paper under timed conditions.
- Use elimination and dimensional analysis. In numerical problems, check the units of your answer. If an option has the wrong unit or an unreasonable magnitude, eliminate it immediately. This is especially useful in gas law and thermochemistry problems.
Pro Tip: Create a master sheet of all functional group tests (how to identify alcohols, aldehydes, ketones, carboxylic acids, alkenes, etc.) and all industrial processes with their catalysts and conditions. These two sheets alone can help you score 8-10 extra marks in Chemistry.
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