JEE Chemistry Equilibrium MCQs Set 13

Chemistry Objective Questions and Answers: Equilibrium

Review structured MCQ sets for JEE Chemistry Equilibrium. Built according to official JEE guidelines, these downloadable questions support daily revision and core concept reinforcement.

Download Equilibrium MCQs with Answers

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Multiple Choice Questions

Question 1: Which of the following is a non-electrolyte?
(a) \( \ce{NaCl} \)
(b) \( \ce{CaCl2} \)
(c) Sucrose (\( \ce{C12H22O11} \))
(d) \( \ce{CH3COOH} \)
Show Answer & Explanation

Answer: (c) Sucrose (\( \ce{C12H22O11} \))

Explanation:
1. Sucrose dissolves as molecules and gives no ions, so it does not conduct.

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 2: The degree of dissociation of an electrolyte increases with
(a) increasing concentration of the electrolyte
(b) decreasing concentration of the electrolyte
(c) decreasing temperature
(d) presence of a substance yielding a common ion
Show Answer & Explanation

Answer: (b) decreasing concentration of the electrolyte

Explanation:
1. Dilution increases ionisation (Ostwald's dilution law).
2. A common ion suppresses ionisation.

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 3: Molten sodium chloride conducts electricity due to the presence of
(a) free electrons
(b) free ions
(c) free molecules
(d) atoms of sodium and chlorine
Show Answer & Explanation

Answer: (b) free ions

Explanation:
1. On melting, the lattice breaks and the ions \( \ce{Na+} \) and \( \ce{Cl-} \) are free to move.

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 4: An example of a strong electrolyte is
(a) urea
(b) ammonium hydroxide
(c) sugar
(d) sodium acetate
Show Answer & Explanation

Answer: (d) sodium acetate

Explanation:
1. Sodium acetate is an ionic salt that is completely dissociated in water.
2. Urea and sugar are non-electrolytes and \( \ce{NH4OH} \) is a weak electrolyte.

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 5: If \( \alpha \) is the degree of ionisation, C the concentration of a weak electrolyte and \( K_a \) the ionisation constant, then
(a) \( \alpha^2=K_a/C \)
(b) \( \alpha^2=C/K_a \)
(c) \( \alpha=K_a/C \)
(d) \( \alpha=C/K_a \)
Show Answer & Explanation

Answer: (a) \( \alpha^2=K_a/C \)

Explanation:
1. For small \( \alpha \), \( K_a=C\alpha^2 \), so \( \alpha=\sqrt{K_a/C} \).

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 6: The theory of ionisation was given by
(a) Rutherford
(b) Graham
(c) Faraday
(d) Arrhenius
Show Answer & Explanation

Answer: (d) Arrhenius

Explanation:
1. Arrhenius proposed that electrolytes dissociate into ions in solution.

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 7: An ionising solvent has
(a) a low dielectric constant
(b) a high dielectric constant
(c) a dielectric constant equal to 1
(d) a high melting point
Show Answer & Explanation

Answer: (b) a high dielectric constant

Explanation:
1. A high dielectric constant reduces the attraction between oppositely charged ions, so ions separate easily (water, 80).

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 8: The extent of ionisation of an electrolyte increases
(a) with an increase in the concentration of solute
(b) on adding excess water to the solution
(c) on decreasing the temperature of the solution
(d) on stirring the solution vigorously
Show Answer & Explanation

Answer: (b) on adding excess water to the solution

Explanation:
1. Dilution increases the degree of ionisation.

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 9: Which is generally true about ionic compounds?
(a) They have low boiling points
(b) They have low melting points
(c) They are soluble in non-polar solvents
(d) They conduct electricity in the fused state
Show Answer & Explanation

Answer: (d) They conduct electricity in the fused state

Explanation:
1. Ionic compounds have high melting and boiling points.
2. In the fused state the ions are free to move and carry current.

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 10: For a weak acid HA, Ostwald's dilution law is represented by
(a) \( K_a=\frac{C\alpha}{1-\alpha^2} \)
(b) \( K_a=\frac{C\alpha^2}{1-\alpha} \)
(c) \( K_a=\frac{\alpha^2}{C(1-\alpha)} \)
(d) \( K_a=\frac{C^2\alpha}{1-\alpha} \)
Show Answer & Explanation

Answer: (b) \( K_a=\frac{C\alpha^2}{1-\alpha} \)

Explanation:
1. \( \ce{HA <=> H+ + A-} \) with concentrations C(1 - \( \alpha \)), \( C\alpha \), \( C\alpha \).
2. So \( K_a=\frac{C\alpha\cdot C\alpha}{C(1-\alpha)}=\frac{C\alpha^2}{1-\alpha} \).

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 11: Acetic acid is a weak electrolyte because
(a) its molecular weight is high
(b) it is a covalent compound
(c) it is ionised only to a small extent
(d) it is highly unstable
Show Answer & Explanation

Answer: (c) it is ionised only to a small extent

Explanation:
1. A weak electrolyte is only partially dissociated in solution.

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 12: Which of the following does not affect the degree of ionisation?
(a) Temperature
(b) Concentration
(c) Type of solvent
(d) Passing a current
Show Answer & Explanation

Answer: (d) Passing a current

Explanation:
1. Ionisation depends on temperature, dilution and solvent, not on the passage of current.

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 13: The addition of a polar solvent to a solid electrolyte results in
(a) polarisation
(b) association
(c) ionisation
(d) electron transfer
Show Answer & Explanation

Answer: (c) ionisation

Explanation:
1. Polar solvent molecules surround and separate the ions of the solid, producing ionisation.

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 14: The hydrogen ion concentration in a weak acid of dissociation constant \( K_a \) and concentration c is nearly equal to
(a) \( \sqrt{K_a/c} \)
(b) \( \sqrt{c/K_a} \)
(c) \( K_ac \)
(d) \( \sqrt{K_ac} \)
Show Answer & Explanation

Answer: (d) \( \sqrt{K_ac} \)

Explanation:
1. \( [H^+]=c\alpha=c\sqrt{K_a/c}=\sqrt{K_ac} \).

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 15: In a weak electrolyte solution, the degree of ionisation is
(a) proportional to dilution
(b) proportional to the concentration of the electrolyte
(c) proportional to the square root of dilution
(d) reciprocal of dilution
Show Answer & Explanation

Answer: (c) proportional to the square root of dilution

Explanation:
1. \( \alpha=\sqrt{K_aV} \) where V is the dilution (volume containing 1 mole).

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 16: The best conductor of electricity among the following 1.0 M solutions is
(a) boric acid
(b) acetic acid
(c) sulphuric acid
(d) phosphoric acid
Show Answer & Explanation

Answer: (c) sulphuric acid

Explanation:
1. Sulphuric acid is a strong acid and gives the highest concentration of ions.

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 17: Dissociation constants of some acids at 25 C are \( 1.4\times10^{-2} \), \( 1.6\times10^{-4} \), \( 4.4\times10^{-10} \) and \( 4.3\times10^{-7} \). The strongest acid has the dissociation constant
(a) \( 1.4\times10^{-2} \)
(b) \( 1.6\times10^{-4} \)
(c) \( 4.4\times10^{-10} \)
(d) \( 4.3\times10^{-7} \)
Show Answer & Explanation

Answer: (a) \( 1.4\times10^{-2} \)

Explanation:
1. A larger \( K_a \) means a stronger acid.

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 18: In the equilibrium \( \ce{HClO4 + H2O <=> H3O+ + ClO4-} \), the correct statement is
(a) \( \ce{HClO4} \) is the conjugate acid of \( \ce{H2O} \)
(b) \( \ce{H3O+} \) is the conjugate base of \( \ce{H2O} \)
(c) \( \ce{H2O} \) is the conjugate acid of \( \ce{H3O+} \)
(d) \( \ce{ClO4-} \) is the conjugate base of \( \ce{HClO4} \)
Show Answer & Explanation

Answer: (d) \( \ce{ClO4-} \) is the conjugate base of \( \ce{HClO4} \)

Explanation:
1. An acid and the species formed by loss of a proton form a conjugate pair.
2. Losing a proton, \( \ce{HClO4} \) gives \( \ce{ClO4-} \), its conjugate base.

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 19: Which one of the following can be classified as a Bronsted base?
(a) \( \ce{NO3-} \)
(b) \( \ce{H3O+} \)
(c) \( \ce{NH4+} \)
(d) \( \ce{CH3COOH} \)
Show Answer & Explanation

Answer: (a) \( \ce{NO3-} \)

Explanation:
1. A Bronsted base accepts a proton; \( \ce{NO3-} \) can accept a proton, while the others are proton donors.

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 20: An aqueous solution of ammonia consists of
(a) \( \ce{H+} \)
(b) \( \ce{OH-} \)
(c) \( \ce{NH4+} \)
(d) \( \ce{NH4+} \) and \( \ce{OH-} \) (along with \( \ce{NH3} \))
Show Answer & Explanation

Answer: (d) \( \ce{NH4+} \) and \( \ce{OH-} \) (along with \( \ce{NH3} \))

Explanation:
1. \( \ce{NH3 + H2O <=> NH4+ + OH-} \) is only partly ionised.

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 21: The strength of an acid depends on its tendency to
(a) accept protons
(b) donate protons
(c) accept electrons
(d) donate electrons
Show Answer & Explanation

Answer: (b) donate protons

Explanation:
1. In the Bronsted-Lowry sense, a stronger acid donates a proton more readily.

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 22: Which of the following is not an electrophile?
(a) \( \ce{AlCl3} \)
(b) \( \ce{BF3} \)
(c) \( \ce{(CH3)3C+} \)
(d) \( \ce{NH3} \)
Show Answer & Explanation

Answer: (d) \( \ce{NH3} \)

Explanation:
1. Electrophiles are electron-deficient. \( \ce{NH3} \) has a lone pair and is a nucleophile.

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 23: In the reaction \( \ce{NH3 + H2O <=> NH4+ + OH-} \), the acid in the forward reaction is
(a) \( \ce{NH3} \)
(b) \( \ce{H+} \)
(c) \( \ce{NH4+} \)
(d) \( \ce{H2O} \)
Show Answer & Explanation

Answer: (d) \( \ce{H2O} \)

Explanation:
1. \( \ce{H2O} \) donates a proton to \( \ce{NH3} \) and gives \( \ce{OH-} \).

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 24: With reference to protonic acids, which of the following is correct?
(a) \( \ce{PH3} \) is more basic than \( \ce{NH3} \)
(b) \( \ce{PH3} \) is less basic than \( \ce{NH3} \)
(c) \( \ce{PH3} \) is equally basic as \( \ce{NH3} \)
(d) \( \ce{PH3} \) is amphoteric while \( \ce{NH3} \) is basic
Show Answer & Explanation

Answer: (b) \( \ce{PH3} \) is less basic than \( \ce{NH3} \)

Explanation:
1. N is smaller and more electronegative than P, so its lone pair is more available: \( \ce{NH3} \) is the stronger base.

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

Question 25: In the reaction \( \ce{HC2O4- + PO4^3- <=> HPO4^2- + C2O4^2-} \), the two Bronsted bases are
(a) \( \ce{HC2O4-} \) and \( \ce{PO4^3-} \)
(b) \( \ce{HPO4^2-} \) and \( \ce{C2O4^2-} \)
(c) \( \ce{HC2O4-} \) and \( \ce{HPO4^2-} \)
(d) \( \ce{PO4^3-} \) and \( \ce{C2O4^2-} \)
Show Answer & Explanation

Answer: (d) \( \ce{PO4^3-} \) and \( \ce{C2O4^2-} \)

Explanation:
1. \( \ce{PO4^3-} \) accepts a proton in the forward direction and \( \ce{C2O4^2-} \) accepts one in the reverse direction.

Teacher's Note:
1. Recall the definition (Arrhenius, Bronsted-Lowry or Lewis) that the question is based on.
2. For a conjugate pair, add or remove one proton; a strong acid has a weak conjugate base.

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Multiple Choice Questions (MCQs) for JEE Chemistry Equilibrium

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