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MCQ on Class 11 Chemistry Chapter 7 Chemical Equilibrium

Questions
1 Which of the following will produce a buffer solution when mixed in equal volumes?
A 0.1 mol dm–3 NH4OH and 0.1 mol dm–3 HCl
B 0.05 mol dm–3 NH4OH and 0.1 mol dm–3 HCl
C 0.1 mol dm–3 NH4OH and 0.05 mol dm–3 HCl
D 0.1 mol dm–3 CH4COONa and 0.1 mol dm–3 NaOH

Answer:0.1 mol dm–3 NH4OH and 0.05 mol dm–3 HCl
2 The acidity of BF3 can be explained based on which of the following concepts?
A Arrhenius concept
B Bronsted Lowry concept
C Lewis concept
D Bronsted Lowry as well as Lewis concept.

Answer:Lewis concept
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3 Ka, 2Ka and 3Ka is the respective ionisation constants for the following reactions.

H2S ⇌ H+ + HS–

HS– ⇌ H+ + S2–

H2S ⇌ 2H+ + S2–

The correct relationship between Ka1 , Ka2 and Ka3 is

A Ka3 = Ka1 × Ka2
B Ka3 = Ka1 + Ka2
C Ka3 = Ka1 – Ka2
D Ka3 = Ka1 /Ka2

Answer:Ka3 = Ka1 × Ka2
4 The ionisation constant of an acid, Ka, is the measure of the strength of an acid. The Ka values of acetic acid, hypochlorous acid and formic acid are 1.74 × 10–5, 3.0 × 10–8 and 1.8 × 10–4 respectively. Which of the following orders of pH of 0.1 mol dm–3 solutions of these acids are correct?
A acetic acid > hypochlorous acid > formic acid
B hypochlorous acid > acetic acid > formic acid
C formic acid > hypochlorous acid > acetic acid
D formic acid > acetic acid > hypochlorous acid

Answer:formic acid > acetic acid > hypochlorous acid
5 The pH of neutral water at 25°C is 7.0. As the temperature increases, ionization of water increases, however, the concentration of H+ ions and OH– ions are equal. What will be the pH of pure water at 60°C?
A Equal to 7.0
B Greater than 7.0
C Less than 7.0
D Equal to zero

Answer:Less than 7.0
6 When hydrochloric acid is added to cobalt nitrate solution at room temperature, the following reaction takes place and the reaction mixture becomes blue. On cooling the mixture it becomes pink. Based on this information mark the correct answer.

[Co (H2O)6]3+ (aq) + 4Cl–(aq) ⇌ [CoCl4]2– (aq) + 6H2O (l)

(pink) (blue)
A ∆H > 0 for the reaction
B ∆H < 0 for the reaction
C ∆H = 0 for the reaction
D The sign of ∆H cannot be predicted based on this information.

Answer:∆H > 0 for the reaction
7 Which of the following statements is incorrect?
A In equilibrium mixture of ice and water kept in perfectly insulated flask mass of ice and water does not change with time.
B The intensity of red colour increases when oxalic acid is added to a solution containing iron (III) nitrate and potassium thiocyanate.
C On addition of the catalyst, the equilibrium constant value is not affected.
D The equilibrium constant for a reaction with negative ∆H value decreases as the temperature increases.

Answer:The intensity of red colour increases when oxalic acid is added to a solution containing iron (III) nitrate and potassium thiocyanate.
8 PCl5, PCl3 and Cl2 are at equilibrium at 500K in a closed container and their concentrations are 0.8 × 10–3 mol L–1, 1.2 × 10–3 mol L–1 and 1.2 × 10–3 mol L–1 respectively. The value of Kc for the reaction PCl5 (g)  PCl3 (g) + Cl2 (g) will be
A 1.8 × 103 mol L–1
B 1.8 × 10–3
C 1.8 × 10–3 L mol–1
D 0.55 × 104

Answer:1.8 × 10–3
9 Which of the following is not a general characteristic of equilibria involving physical processes?
A Equilibrium is possible only in a closed system at a given temperature.
B All measurable properties of the system remain constant.
C All the physical processes stop at equilibrium.
D The opposing processes occur at the same rate and there is dynamic but stable condition.

Answer:All the physical processes stop at equilibrium.
10 For the reaction H2(g) + I2(g) → 2HI (g), the standard free energy is ∆G > 0.

The equilibrium constant (K ) would be __________.

A K = 0
B K > 1
C K = 1
D K < 1

Answer:K < 1
11 Which of the following will produce a buffer solution when mixed in equal volumes ?
A 0.1 mol dm–3 NH4OH and 0.1 mol dm–3 HCl
B 0.05 mol dm–3 NH4OH and 0.1 mol dm–3 HCl
C 0.1 mol dm–3 NH4OH and 0.05 mol dm–3 HCl
D 0.1 mol dm–3 CH4COONa and 0.1 mol dm–3 NaOH

Answer:0.1 mol dm–3 NH4OH and 0.05 mol dm–3 HCl
12 We know that the relationship between Kc and Kp is

Kp = Kc (RT)Δ n

What would be the value of Δn for the reaction

NH4Cl (s) ⇔ NH3 (g) + HCl (g)

A 1
B 0.5
C 1.5
D 2

Answer:2
13 For the reaction H2(g) + I2(g) ⇔ 2HI (g), the standard free energy is ΔG⊖ > 0. The equilibrium constant (K ) would be __________.
A K = 0
B K > 1
C K = 1
D K < 1

Answer:K < 1
14 Which of the following is not a general characteristic of equilibria involving physical processes?
A Equilibrium is possible only in a closed system at a given temperature.
B All measurable properties of the system remain constant.
C All the physical processes stop at equilibrium.
D The opposing processes occur at the same rate and there is dynamic but stable condition.

Answer:All the physical processes stop at equilibrium.
15 PCl5, PCl3 and Cl2 are at equilibrium at 500K in a closed container and their concentrations are 0.8 × 10–3 mol L–1, 1.2 × 10–3 mol L–1 and 1.2 × 10–3 mol L–1 respectively. The value of Kc for the reaction PCl5 (g) ⇔ PCl3 (g) + Cl2 (g) will be
A 1.8 × 103 mol L–1
B 1.8 × 10–3
C 1.8 × 10–3 L mol–1
D 0.55 × 104

Answer:1.8 × 10–3
16 Which of the following statements is incorrect?
A In equilibrium mixture of ice and water kept in perfectly insulated flask mass of ice and water does not change with time.
B The intensity of red colour increases when oxalic acid is added to a solution containing iron (III) nitrate and potassium thiocyanate.
C On addition of catalyst the equilibrium constant value is not affected.
D Equilibrium constant for a reaction with negative ΔH value decreases as the temperature increases.

Answer:The intensity of red colour increases when oxalic acid is added to a solution containing iron (III) nitrate and potassium thiocyanate.
17 The pH of neutral water at 25°C is 7.0. As the temperature increases, ionisation of water increases, however, the concentration of H+ ions and OH– ions are equal. What will be the pH of pure water at 60°C?
A Equal to 7.0
B Greater than 7.0
C Less than 7.0
D Equal to zero

Answer:Less than 7.0
18 The ionisation constant of an acid, Ka, is the measure of strength of an acid. The Ka values of acetic acid, hypochlorous acid and formic acid are 1.74 × 10–5, 3.0 × 10–8 and 1.8 × 10–4 respectively. Which of the following orders of pH of 0.1 mol dm–3 solutions of these acids is correct?
A acetic acid > hypochlorous acid > formic acid
B hypochlorous acid > acetic acid > formic acid
C formic acid > hypochlorous acid > acetic acid
D formic acid > acetic acid > hypochlorous acid

Answer: formic acid > acetic acid > hypochlorous acid
19 Ka1, Ka2 and Ka3 are the respective ionisation constants for the following reactions

H2S ⇔ H+ + HS–

HS– ⇔ H+ + S2–

H2S ⇔ 2H+ + S2–

The correct relationship between Ka1, Ka2 and Ka3 is

A Ka3 = Ka1 * Ka2
B Ka3 = Ka1 + Ka2
C Ka3 = Ka1 – Ka2
D Ka3 = Ka1 / Ka2

Answer:Ka3 = Ka1 * Ka2
20 Acidity of BF3 can be explained on the basis of which of the following concepts?
A Arrhenius concept
B Bronsted Lowry concept
C Lewis concept
D Bronsted Lowry as well as Lewis concept.

Answer:Lewis concept

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