DSSSB PGT Chemistry Question paper 2025

this exam was conducted on 23 July 2025 Question paper

Section: Discipline 1

Q.1 a mixture of gas contains 2 mole oxygen 3 mole of nitrogen and 1 mole of helium at a total pressure of 10 atm. According to Dalton, s law of partial pressure, what is the partial pressure of nitrogen in the mixture

1. 10 atm          2. 7 atm             3. 3 atm             4. 5 atm

Ans is 5 atm

Q.2 According to Dalton’s Law of Partial Pressure, the total pressure exerted by a mixture of non-reacting gases is:

1. equal to the highest partial pressure of any gas in the mixture
2. the product of the partial pressures of individual gases
3. independent of the number of gases present in the mixture
4. the sum of the partial pressures of individual gases

Answer: 4. the sum of the partial pressures of individual gases

Q.3 Which law states that the dissociation constant (Kc) is inversely proportional to dilution (V)?

1. Law of mass action
2. Ostwald’s dilution law
3. Hardy-Schulze law
4. Law of osmotic pressure

Answer: 2. Ostwald’s dilution law

Q.4 Which law is illustrated by the fact that carbon forms two different oxides, CO and CO₂?

1. Law of Reciprocal Proportions
2. Law of Definite Proportions
3. Law of Multiple Proportions
4. Law of Conservation of Mass

Answer: 3. Law of Multiple Proportions

Q.5 Consider the following statements and select the most appropriate answer.
Statement-I: Many properties of matter, such as length, area, volume, etc., are quantitative in nature.
Statement-II: Any quantitative observation or measurement is represented by a number followed by units in which it is measured.

1. Statement-I is false but statement-II is true.
2. Statement-I is true but statement-II is false.
3. Both the statements are true.
4. Both the statements are false.

Answer: 3. Both the statements are true.

Q.6 A certain metal crystallises in a body-centred cubic (BCC) lattice with an atomic radius of 2.5 Å. What is the length of its unit cell edge?

1. 5.77 Å
2. 3.62 Å
3. 4.33 Å
4. 6.12 Å

Answer: 1. 5.77 Å

Q.7 Why did Rutherford’s atomic model fail to explain the stability of atoms?

1. It could not explain the presence of neutrons in the nucleus.
2. It suggested that electrons are stationary around the nucleus.
3. It could not explain the quantised nature of electron orbits.
4. It did not account for the repulsion between electrons.

Answer: 3. It could not explain the quantised nature of electron orbits.

Q.8 Which of the following statements are true?
i. In scientific notation, numbers can be represented in the form N × 10n, where n is an exponent having positive or negative values and N is a number (called digit term) which varies between 1.000… and 9.999….
ii. We can write 232.508 as 2.32508 × 102 in scientific notation.
iii. Similarly, 0.00016 can be written as 1.6 × 10–4 in scientific notation.

1. i and iii only
2. ii and iii only
3. i, ii and iii
4. i and ii only

Answer: 3. i, ii and iii

Q.9 How does the shape of the Maxwell-Boltzmann probability distribution curve change with an increase in temperature?

1. The area under the curve increases significantly.
2. The peak shifts to higher speeds and becomes broader.
3. The number of molecules with the most probable speed increases significantly.
4. The peak shifts to lower speeds and becomes narrower.

Answer: 2. The peak shifts to higher speeds and becomes broader.

Q.10 Often while calculating, there is a need to convert units from one system to the other. The method used to accomplish this is called:
i. Factor label method
ii. Unit factor method
iii. Dimensional analysis

1. i and iii only
2. i, ii and iii
3. i and ii only
4. ii and iii only

Answer: 2. i, ii and iii

Q.11 Isotopes are satisfied from which of the following?

1. Same number of protons
2. Different atomic numbers
3. Different number of electrons
4. Same number of neutrons

Answer: 1. Same number of protons

Q.12 The forces of attraction between gas molecules are negligible at:

1. low pressure
2. critical temperature
3. high pressure
4. low temperature

Answer: 1. low pressure

Q.13 A metal crystallises in a face-centred cubic (FCC) lattice with an atomic mass of 108 g/mol and a unit cell edge length of 4.08 Å. What is the density of the metal?

1. 11.2 g/cm³
2. 9.78 g/cm³
3. 8.92 g/cm³
4. 10.5 g/cm³

Answer: 4. 10.5 g/cm³

Q.14 Consider the following statements and select the most appropriate answer.
Statement-I: One atomic mass unit is defined as a mass exactly equal to one-twelfth of the mass of one carbon – 12 atom.
Statement-II: Molecular mass is the sum of atomic masses of the elements present in a molecule. It is obtained by multiplying the atomic mass of each element by the number of its atoms and adding them together.

1. Both the statements are true.
2. Statement-I is true but statement-II is false.
3. Both the statements are false.
4. Statement-I is false but statement-II is true.

Answer: 1. Both the statements are true.

Q.15 In the Maxwell distribution, the average velocity is inversely proportional to:

1. temperature
2. the total number of molecules
3. molecular mass
4. pressure

Answer: 3. molecular mass

Q.16 If a magnetic field is not passed through the superconductors, it is known as the:

1. Joule Thomson effect
2. Compton effect
3. Meissner effect
4. Raman effect

Answer: 3. Meissner effect

Q.17 Which of the following best describes the nature of a wave governed by the classical wave equation?

1. It is a localised disturbance that does not propagate.
2. It represents the oscillation of particles at a single point without transfer of energy.
3. It describes the motion of a periodic disturbance travelling through a medium.
4. It is applicable only to quantum mechanical wave functions.

Answer: 3. It describes the motion of a periodic disturbance travelling through a medium.

Q.18 In an ionic crystal exhibiting only Schottky defects, how does the defect influence the electrical conductivity of the solid at constant temperature?

1. Conductivity increases because Schottky defects introduce free electrons.
2. Conductivity decreases as vacancies block charge movement.
3. Conductivity increases due to increased ionic mobility.
4. Conductivity remains unchanged since there are no free charge carriers.

Answer: 3. Conductivity increases due to increased ionic mobility.

Q.19 Crystalline solids do not have:

1. definite heat of fusion
2. sharp melting point
3. definite geometric shape
4. isotropic nature

Answer: 4. isotropic nature

Q.20 The configuration 1s³ is forbidden by the:

1. Fajan’s rule
2. Hund’s rule
3. Pauli exclusion principle
4. Octet rule

Answer: 3. Pauli exclusion principle

Section: Discipline2

Q.1 Macromolecular colloids are generally classified as:

1. lyophilic colloids
2. micelles
3. suspension
4. suspensions

Answer: 1. lyophilic colloids

Q.2 Which factor primarily determines how effectively an electrolyte can precipitate a colloidal solution?

1. The temperature of the solution
2. The charge on the precipitating ion
3. The volume of the colloidal solution
4. The colour of the colloidal particles

Answer: 2. The charge on the precipitating ion

Q.3 What happens in the solution when the ionic product (Kip) of a salt exceeds its solubility product (Ksp)?

1. No change occurs in the solubility.
2. The solution remains unsaturated.
3. Excess salt begins to precipitate.
4. The solution stays at equilibrium.

Answer: 3. Excess salt begins to precipitate.

Q.4 A chemist conducts a conductometric titration on an unknown acid using NaOH. The conductivity first drops sharply and then gradually increases after the equivalence point. Which of the following is the most probable identity of the acid?

1. HCl (Strong Acid)
2. CH₃COOH (Weak Acid)
3. H₃PO₄ (Triprotic Acid)
4. H₂SO₄ (Diprotic Acid)

Answer: 2. CH₃COOH (Weak Acid)

Q.5 Which of the following is an example of adsorption?

1. Silica gel
2. Chemical reaction between gas and a metal
3. Water vapour absorbed by sponge
4. Liquid absorbed by a solid

Answer: 1. Silica gel

Q.6 The strength of an acid depends on ___________.

1. the total concentration of H+ ions in aqueous solutions
2. the tendency to release the electron pair
3. the tendency to gain the electron pair
4. the total concentration of electron pairs in aqueous solutions

Answer: 1. the total concentration of H+ ions in aqueous solutions

Q.7 When are the binding forces strong between the adsorbate and the adsorbent?

1. Electrosorption
2. Physiosorption
3. Chemisorption
4. Biosorption

Answer: 3. Chemisorption

Q.8 Which of the following aqueous salt solutions will be acidic in nature?

1. Potassium chloride (KCl)
2. Sodium carbonate (Na2CO3)
3. Ammonium chloride (NH4Cl)
4. Sodium acetate (CH3COONa)

Answer: 3. Ammonium chloride (NH4Cl)

Q.9 Enzyme catalysis follows which of the following mechanisms?

1. Transition State Theory
2. Collision Theory
3. Lock-and-Key Mechanism
4. Michaelis-Menten Mechanism

Answer: 4. Michaelis-Menten Mechanism

Q.10 Which of the following changes will generally increase the rate of a chemical reaction?

1. Decreasing the concentration of the reactants
2. Adding a negative catalyst
3. Lowering the temperature of the reaction mixture
4. Increasing the surface area of the reactants

Answer: 4. Increasing the surface area of the reactants

Q.11 Which of the following experimental observations confirms the presence of electric charge on colloidal particles?

1. The colloidal solution exhibits Brownian motion.
2. Coagulation occurs when colloidal solutions are filtered through fine pores.
3. Particles migrate toward oppositely charged electrodes during electrophoresis.
4. Colloidal particles show the Tyndall effect under light.

Answer: 3. Particles migrate toward oppositely charged electrodes during electrophoresis.

Q.12 Which law states that the rate of chemical reaction is proportional to the active masses of the reactants?

1. Law of osmotic pressure
2. Hardy-Schulze law
3. Law of mass action
4. Ostwald’s dilution law

Answer: 3. Law of mass action

Q.13 Which analytical technique utilises electrophoresis for the separation of biomolecules based on their charge-to-mass ratio?

1. Gel electrophoresis
2. NMR spectroscopy
3. Gas chromatography (GC)
4. X-ray diffraction (XRD)

Answer: 1. Gel electrophoresis

Q.14 Which of the following statements correctly describes a limitation of the Freundlich adsorption isotherm?

1. It does not apply to gases adsorbed on solids.
2. It cannot explain adsorption at low pressures.
3. It assumes adsorption is a chemical process only.
4. It fails at high pressures when monolayer formation occurs.

Answer: 4. It fails at high pressures when monolayer formation occurs.

Q.15 The equilibrium reaction PCl5(g) ⇌ PCl3(g) + Cl2(g) is at equilibrium. What will happen if more Cl2 gas is added to the system?

1. The reaction remains unaffected.
2. The reaction shifts to the right, forming more PCl3.
3. The reaction stops completely.
4. The reaction shifts to the left, forming more PCl5.

Answer: 4. The reaction shifts to the left, forming more PCl5.

Q.16 Which of the following is an INCORRECT statement about acids and bases?

1. Solutions of substances that show different colours in acidic, basic, and neutral solutions are called indicators.
2. An acid and a base neutralise each other to form a salt, and salt is always neutral.
3. Acids turn blue litmus red and bases turn red litmus blue.
4. Acids are sour in taste whereas bases are bitter and soapy to touch.

Answer: 2. An acid and a base neutralise each other to form a salt, and salt is always neutral.

Q.17 Which of the following is an example of a sorption process?

1. Sugar dissolving in water
2. Water vapour condensing on a cold glass
3. Formation of a soap micelle in water
4. Chalk absorbing ink

Answer: 4. Chalk absorbing ink

Q.18 Enzyme catalysis is highly specific due to:

1. high energy bonds within the enzyme that release energy
2. unique active sites that match specific substrate molecules
3. irreversible interactions between enzyme and substrate
4. constant turnover rate, regardless of external conditions

Answer: 2. unique active sites that match specific substrate molecules

Q.19 Which of the following pairs represents a correct Brønsted-Lowry conjugate acid-base pair?

1. H2SO4/SO4²⁻
2. NH3/NH2⁻
3. H2O/OH⁻
4. H3O+/HCl

Answer: 3. H2O/OH⁻

Q.20 An emulsion is a dispersion of a _________.

1. gas in a solid
2. gas in a liquid
3. liquid in a liquid
4. liquid in a solid

Answer: 3. liquid in a liquid

Section: Discipline3

Q.1 Which of the following factors affects the quantum yield of a luminescent process?

1. Excitation wavelength only
2. Molar mass of the luminescent molecule
3. Temperature and presence of quenchers
4. Speed of light in a medium

Answer: 3. Temperature and presence of quenchers

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Q.2 Refer to the three statements given below and choose the correct option.
Statement A: In a redox reaction, oxidation involves the loss of electrons.
Statement B: The standard hydrogen electrode (SHE) has a reduction potential of 0.00 V.
Statement C: All electrochemical reactions are non-spontaneous.

1. Only Statement A is true
2. Only Statements A and B are true
3. Only Statements B and C are true
4. Statements A, B, and C, all are true

Answer: 2. Only Statements A and B are true

Q.3 What role does the salt bridge play in a galvanic cell with respect to electrical conductivity?

1. Increases resistivity of the electrodes
2. Increases resistance by blocking ion flow
3. Decreases resistance by allowing ion migration
4. Acts as an insulator

Answer: 3. Decreases resistance by allowing ion migration

Q.4 Consider a generic redox reaction whose standard cell potential is calculated by the formula: E° = (RT/nF) /ln K. If experimental measurements show that the computed E° value is approximately 10% lower than the measured potential at 298 K, which of the following factors is most likely responsible for the discrepancy?

1. Neglect of activity coefficients (i.e., using concentrations instead of activities) in calculating K
2. An incorrect estimation of the number of electrons (n) transferred
3. The assumption that the gas constant (R) varies with temperature
4. A systematic error in the temperature measurement

Answer: 1. Neglect of activity coefficients (i.e., using concentrations instead of activities) in calculating K

Q.5 For a solution containing two volatile components A and B, if the mole fraction of the component with the higher vapour pressure is increased, what happens to the total vapour pressure of the solution?

1. The total vapour pressure will remain the same.
2. The total vapour pressure will decrease.
3. The total vapour pressure will first increase and then decrease.
4. The total vapour pressure will increase.

Answer: 4. The total vapour pressure will increase.

Q.6 Using Kohlrausch’s law, the molar conductivity at infinite dilution (Λ₀m) for a weak electrolyte is obtained by:

1. taking the average of molar conductivities at different concentrations
2. directly measuring at infinite dilution
3. extrapolating experimental Λm vs. concentration data
4. using conductance bridge measurement

Answer: 3. extrapolating experimental Λm vs. concentration data

Q.7 Which of the following statements is true about molecularity of a reaction?

1. It is always equal to the order of the reaction.
2. It can be zero.
3. It is the number of reactant molecules in the chemical reaction.
4. It can be fractional.

Answer: 3. It is the number of reactant molecules in the chemical reaction.

Q.8 Which substance is used for oxidising fluorides to fluorine from the electrochemical series?

1. Copper
2. Zinc
3. Silver
4. Cannot be oxidised

Answer: 4. Cannot be oxidised

Q.9 Which of the following compounds has the correct Lewis structure where all atoms follow the octet rule?

1. SF6 with six single bonds between sulfur and fluorine
2. NO with a single bond between nitrogen and oxygen
3. CO2 with two double bonds between carbon and oxygen
4. BF3 with three single bonds between boron and fluorine

Answer: 3. CO2 with two double bonds between carbon and oxygen

Q.10 To accurately calculate the molecular mass of a solute using colligative properties, which of the following conditions must be met?

1. The solution should be dilute and follow ideal behaviour.
2. The solute must be volatile.
3. The solution must be concentrated.
4. The solute should not dissolve in the solvent.

Answer: 1. The solution should be dilute and follow ideal behaviour.

Q.11 A salt bridge is used in an electrochemical cell to:

1. increase the voltage of the cell
2. prevent mixing of solutions but allow ion movement
3. precipitate unwanted ions in the solution
4. complete the circuit by allowing electron flow

Answer: 2. prevent mixing of solutions but allow ion movement

Q.12 What is the molal boiling point elevation constant also called?

1. Dissociation constant
2. Cryoscopic constant
3. Ebullioscopic constant
4. Maxwell–Boltzmann constant

Answer: 3. Ebullioscopic constant

Q.13 Which of the following is necessary for hydrogen bonding to occur?

1. A hydrogen atom bonded to an electronegative atom
2. A hydrogen atom bonded to a metal atom
3. A hydrogen atom bonded to another hydrogen atom
4. A hydrogen atom in a non polar molecule

Answer: 1. A hydrogen atom bonded to an electronegative atom

Q.14 A solution of two liquids A and B shows a positive deviation from Raoult’s Law. Which of the following is NOT true for this solution?

1. The intermolecular forces between A and B are weaker than those between A-A and B-B.
2. The solution will exhibit a maximum in the vapour pressure-composition diagram.
3. The vapour pressure of the solution is higher than that predicted by Raoult’s Law.
4. The boiling point of the solution will be higher than that of both pure A and pure B.

Answer: 4. The boiling point of the solution will be higher than that of both pure A and pure B.

Q.15 Which species acts as the reducing agent in the reaction: Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)?

1. Zn
2. Cu
3. Zn²⁺
4. Cu²⁺

Answer: 1. Zn

Q.16 A solution containing one gram equivalent of an electrolyte is known as:

1. molar conductance
2. specific conductance
3. metallic conductance
4. equivalent conductance

Answer: 4. equivalent conductance

Q.17 The potential of an electrode is called the standard electrode potential if the concentration of the ions is unity and the temperature is:

1. 273°C
2. 0°C
3. 25°C
4. 10°C

Answer: 3. 25°C

Q.18 According to Faraday’s First Law of Electrolysis, the mass of a substance deposited at an electrode is directly proportional to:

1. voltage and resistance
2. current and time
3. the concentration of electrolyte
4. the temperature of the solution

Answer: 2. current and time

Q.19 For a reaction mechanism involving the following steps, which step determines the rate, and how is the overall reaction order defined?
A + B → C (slow)
C + D → E (fast)

1. Slow step; reaction order from the first step
2. Fast step; reaction order from the first step
3. Fast step; reaction order from the second step
4. Slow step; reaction order from the second step

Answer: 1. Slow step; reaction order from the first step

Q.20 The unit of resistance is the ohm, symbolised as:

1. ω
2. δ
3. Ω
4. μ

Answer: 3. Ω

Section: Discipline4

Q.1 The thermodynamic potential used to determine the spontaneity of processes under the conditions of constant pressure and temperature is __________.

1. kinetic energy
2. Gibbs free energy
3. Helmholtz energy
4. activation energy

Answer: 2. Gibbs free energy

Q.2 Ionic radii are typically determined by:

1. calculating the atomic mass of an ion
2. determining the number of electrons in an ion
3. measuring the distance between atoms in a covalent molecule
4. measuring the distance between ions in an ionic crystal

Answer: 4. measuring the distance between ions in an ionic crystal

Q.3 How can the degree of freedom (F) in a multiphase system be determined using the number of phases (π) and the number of chemical species (N)?

1. F=2+π−N
2. F=2−π+N
3. F=2−π−N
4. F=2+π+N

Answer: 2. F=2−π+N

Q.4 Consider the following statements and select the most appropriate answer.
Statement-I: Fluorine has the highest electronegativity in the periodic table, that is, 4.
Statement-II: Electronegativity of inert gases is zero.

1. Both the statements are true.
2. Statement-I is true but statement-II is false.
3. Both the statements are false.
4. Statement-I is false but statement-II is true.

Answer: 1. Both the statements are true.

Q.5 According to the Valence Bond Theory (VBT), which of the following is a quantitative interpretation provided by the theory?

1. Predicting the polarity of a bond using electronegativity values
2. Predicting molecular orbitals using the combination of atomic orbitals
3. Estimating bond strength based on the extent of overlap of atomic orbitals
4. Explaining the geometry of molecules based on repulsion between electron pairs

Answer: 3. Estimating bond strength based on the extent of overlap of atomic orbitals

Q.6 If a process has ΔH < 0 and ΔS > 0, what can be concluded about its spontaneity?

1. Always spontaneous
2. Spontaneous only at high temperatures
3. Never spontaneous
4. Spontaneous only at low temperatures

Answer: 1. Always spontaneous

Q.7 Which of the following ions has the smallest radius?

1. Na+
2. Mg2+
3. K+
4. Al3+

Answer: 4. Al3+

Q.8 Which periodic trend decreases across a period but increases down a group?

1. Electronegativity
2. Metallic character
3. Electron gain enthalpy
4. Atomic radius

Answer: 4. Atomic radius

Q.9 What is the result of acidifying barium peroxide followed by vacuum evaporation to remove excess water?

1. Barium sulphate
2. Hydrogen peroxide
3. Oxygen gas
4. Barium hydroxide

Answer: 2. Hydrogen peroxide

Q.10 In which of the following molecules does the central atom use d-orbitals in its hybridisation?

1. H2O
2. PCl5
3. CO2
4. NH3

Answer: 2. PCl5

Q.11 Crude sodium chloride, generally obtained by crystallisation of brine solution, contains______, ______ and ______ as impurities.

1. Calcium oxalate, magnesium chloride, calcium chloride
2. Calcium sulphate, magnesium chloride, calcium chloride
3. Calcium sulphate, magnesium hydroxide, calcium chloride
4. Calcium sulphate, magnesium chloride, calcium phosphate

Answer: 2. Calcium sulphate, magnesium chloride, calcium chloride

Q.12 Peroxodisulfate is formed by the electrolytic oxidation of ___________, on hydrolysis yields hydrogen peroxide.

1. Acidified nitrate solutions at high current density
2. Acidified sulfate solutions at high current density
3. Acidified chloride solutions at low current density
4. Acidified sulfate solutions at low current density

Answer: 2. Acidified sulfate solutions at high current density

Q.13 Energy conservation is given by the ________ law of thermodynamics.

1. third
2. zeroth
3. second
4. first

Answer: 4. first

Q.14 Hydrogen bonding in DNA is primarily responsible for:

1. the primary structure of DNA
2. the replication of DNA
3. the folding of individual DNA strands
4. the formation of the double helix structure

Answer: 4. the formation of the double helix structure

Q.15 Which of the following ions would have the smallest ionic radius?

1. Mg2+
2. F–
3. O2–
4. Na+

Answer: 1. Mg2+

Q.16 What is the term that describes a compound where hydrogen is bonded to an electropositive element or group?

1. Hydroxide
2. Hydrogen halide
3. Hydronium
4. Hydride

Answer: 4. Hydride

Q.17 What happens to the entropy of a perfect crystal as the temperature approaches absolute zero?

1. It becomes unpredictable.
2. It approaches infinity.
3. It approaches zero.
4. It approaches one.

Answer: 3. It approaches zero.

Q.18 Why is hydrogen placed in Group 1 (alkali metals) of the periodic table?

1. Because it has one s-electron
2. Because it has a full outer shell
3. Because it forms diatomic molecules
4. Because it has two s-electrons

Answer: 1. Because it has one s-electron

Q.19 What concept serves as a foundation for establishing criteria to identify spontaneous processes and various equilibrium states?

1. Gibbs free energy
2. Internal energy
3. Enthalpy
4. Entropy

Answer: 4. Entropy

Q.20 Select the option that is correct regarding the following two statements labelled Assertion (A) and Reason (R).
Assertion (A): Acidity of o-nitrophenol is less compared with m-nitrophenol and p-nitrophenol.
Reason (R): There is intramolecular hydrogen bond in o-nitrophenol.

1. Both A and R are true, and R is the correct explanation of A.
2. A is true, but R is false.
3. Both A and R are true, and R is not the correct explanation of A.
4. A is false, but R is true.

Answer: 4. A is false, but R is true.

Section: Discipline 5

Q.1 Pseudohalide CN⁻. resembles Cl⁻, Br⁻ and I⁻ in which of the following respects?
i. It forms an acid HCN.
ii. It can be oxidised to form a molecule cyanogen (CN)2.
iii. AgCN is insoluble in water but soluble in ammonia, as is AgCl.

1. i, ii and iii
2. i and iii only
3. ii and iii only
4. i and ii only

Answer: 1. i, ii and iii

Q.2 Which of the following is a chemical property of borax?

1. It has a high melting point.
2. It dissolves in water.
3. It forms a gel when mixed with glycerin.
4. It reacts with acids to produce boric acid.

Answer: 4. It reacts with acids to produce boric acid.

Q.3 It is a white amorphous powder. It is sparingly soluble in water and its suspension in water is known as milk of lime. It is:

1. calcium carbonate
2. calcium sulphate
3. calcium chloride
4. calcium hydroxide

Answer: 4. calcium hydroxide

Q.4 Select the option that is correct regarding the following statements labelled Assertion (A) and Reason (R).
Assertion (A): Isoelectronic species such as CO, CN⁻ and NO+ are much more reactive than N2.
Reason (R): The bonds are partly polar in CO, CN⁻ and NO+, whilst in N2 they are not.

1. Both A and R are true, and R is the correct explanation of A
2. Both A and R are true, and R is not the correct explanation of A
3. A is false, but R is true
4. A is true, but R is false

Answer: 1. Both A and R are true, and R is the correct explanation of A

Q.5 Consider the following statements and select the most appropriate answer.
Statement-I: Calcium carbonate occurs in nature in several forms like limestone, chalk, marble, etc.
Statement-II: It is used as an antacid, mild abrasive in toothpaste, and a constituent of chewing gum.

1. Statement-I is false but statement-II is true.
2. Both the statements are false.
3. Statement-I is true but statement-II is false.
4. Both the statements are true.

Answer: 4. Both the statements are true.

Q.6 What is the primary method for obtaining pure sodium chloride from brine?

1. Electrolysis
2. Distillation
3. Crystallization
4. Reaction

Answer: 3. Crystallization

Q.7 The difference between Lithium and the rest of the elements of the alkali group are:
i. Lithium is much harder than the other Group 1 metals.
ii. Lithium forms a nitride Li3N. None of the other Group 1 elements forms a nitride.
iii. Lithium reacts directly with carbon to form an ionic carbide. None of the other Group 1 elements form carbide.

1. ii and iii only
2. i and ii only
3. i, ii and iii
4. i and iii only

Answer: 3. i, ii and iii

Q.8 Nitrogen gas is commonly used for ___________.

1. food preservation
2. material production
3. soap manufacturing
4. water purification

Answer: 1. food preservation

Q.9 What is a typical chemical property of boron hydrides?

1. They have a high boiling point.
2. They are insoluble in organic solvents.
3. They can act as Lewis acids.
4. They are non-toxic.

Answer: 3. They can act as Lewis acids.

Q.10 Identify whether the following statements are true or false.
Statements:
I) The most important commercial process for the manufacture of sulphuric acid is the Contact process, in which SO2 is oxidised by air to SO3, using a catalytic surface.
II) Vanadium pentoxide is used as a catalyst in the contact process.

1. Statement I is false but statement II is true.
2. Both the statements are false.
3. Statement I is true but statement II is false.
4. Both the statements are true.

Answer: 4. Both the statements are true.

Q.11 _____________ exhibits several unique properties due to its layered structure and anisotropic nature.

1. Red phosphorus
2. Black phosphorus
3. White phosphorus
4. Violet phosphorus

Answer: 2. Black phosphorus

Q.12 Select the option that is correct regarding the following statements labelled Assertion (A) and Reason (R).
Assertion (A): H3BO3 or (B(OH)3) cannot be titrated satisfactorily with NaOH.
Reason (R): Certain organic polyhydroxy compounds such as glycerol, mannitol or sugars are added to the titration mixture.

1. Both A and R are true, and R is not the correct explanation of A
2. A is false, but R is true
3. Both A and R are true, and R is the correct explanation of A
4. A is true, but R is false

Answer: 4. A is true, but R is false

Q.13 Select the option that is true regarding the following two statements labelled Assertion (A) and Reason (R).
Assertion (A): Chemically, Group 1 elements are very reactive, and tarnish rapidly in dry air.
Reason (R): Alkali metals are kept in kerosene oil.

1. A is true, but R is false.
2. A is false, but R is true.
3. Both A and R are true, and R is not the correct explanation of A.
4. Both A and R are true, and R is the correct explanation of A.

Answer: 4. Both A and R are true, and R is the correct explanation of A.

Q.14 Which of the following statements about extracting s-block elements is NOT true?

1. Beryllium is extracted from beryl by electrolytic reduction.
2. Calcium can be obtained by the electrolysis of fused calcium chloride.
3. Sodium is extracted by the electrolysis of molten sodium chloride.
4. Lithium is extracted using acid treatment and fusion methods followed by electrolysis.

Answer: 1. Beryllium is extracted from beryl by electrolytic reduction.

Q.15 The solubility of lithium compounds in organic solvents is primarily due to their _________.

1. anomalous behaviour that leads to increased covalent character
2. low polarizing power
3. ionic character
4. large size

Answer: 1. anomalous behaviour that leads to increased covalent character

Q.16 Identify whether the following statements are true or false.
Statements:
I) PCl3 is widely used in organic chemistry to convert carboxylic acids to acid chlorides and alcohols to alkyl halides.
II) PCl3 can be oxidised by O2 or P4O10 to give phosphorus oxochloride POCl3.

1. Statement I is true but statement II is false.
2. Both the statements are false.
3. Both the statements are true.
4. Statement I is false but statement II is true.

Answer: 3. Both the statements are true.

Q.17 Match column-I with column-II.
Column-I Transition metal
Column-II Maximum oxidation state
i. Mn
a. +V
ii. Cr
b. +VII
iii. V
c. +VI

1. i-b, ii-c, iii-a
2. i-c, ii-b, iii-a
3. i-a, ii-c, iii-b
4. i-b, ii-a, iii-c

Answer: 1. i-b, ii-c, iii-a

Q.18 How is the electron configuration arranged for the element with an atomic number of 6?

1. 1s² 2s² 2p²
2. 1s² 2s² 2p⁴
3. 1s² 2s² 2p³
4. 1s² 2s² 2p⁶

Answer: 1. 1s² 2s² 2p²

Q.19 Identify whether the following statements are true or false.
Statements:
I) HCl is made by the ‘salt cake’ method. In this method, concentrated H2SO4 is added to rock salt (NaCl).
II) HCl is conveniently made in the laboratory by treating NH4Cl with concentrated H2SO4.

1. Both the statements are false.
2. Both the statements are true.
3. Statement I is true but statement II is false.
4. Statement I is false but statement II is true.

Answer: 2. Both the statements are true.

Q.20 Which of the following statements about silicones is INCORRECT?

1. Alkyl substituted chlorosilanes are the only starting material for manufacture of silicones
2. Silicones are widely used as rubber
3. Silicones are fairly expensive
4. Silicones were originally developed as electrical insulators

Answer: 1. Alkyl substituted chlorosilanes are the only starting material for manufacture of silicones

Read more: DSSSB PGT Chemistry Question paper 2025

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