Equilibrium

Acidity of BF₃ can be explained on the basis of which of the following concepts?

(i) Arrhenius concept

(ii) Bronsted Lowry concept

(iii) Lewis concept

(iv) Bronsted Lowry as well as Lewis concept

K_a1 , K_a2 and K_a3 are the respective ionisation constants for the following reactions.

H₂S $\mathit{}\to$   H⁺ + HS

HS^–  $\mathit{}\to$ H⁺ + S²

 H₂S $\mathit{}\to$ 2H⁺ + S²

The correct relationship between is K_a1 , K_a2 and K_a3

1. K_a3= K_a1 * K_a2
2. K_a3= K_a1 + K_a2
3. K_a3= K_a1 – K_a2
4. K_a3= K_a1 / K_a2

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?

(i) Acetic acid > hypochlorous acid > formic acid

(ii) Hypochlorous acid > acetic acid > formic acid

(iii) Formic acid > hypochlorous acid > acetic acid

(iv) Formic acid > acetic acid > hypochlorous acid

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?

(i) Equal to 7.0

(ii) Greater than 7.0

(iii) Less than 7.0

(iv) Equal to zero

Which of the following statements is incorrect?

(i) In equilibrium mixture of ice and water kept in perfectly insulated flask mass of ice and water does not change with time.

(ii) The intensity of red colour increases when oxalic acid is added to a solution containing iron

(III) nitrate and potassium thiocyanate.

(iii) On addition of catalyst the equilibrium constant value is not affected.

(iv) Equilibrium constant for a reaction with negative ?H value decreases as the temperature increases.

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

(i) 1.8 * 10³ mol L^–1

(ii) 1.8 * 10^–3

(iii) 1.8 * 10^–3 L mol^–1

(iv) 0.55 * 10⁴

Which of the following is not a general characteristic of equilibria involving physical processes?

(i) Equilibrium is possible only in a closed system at a given temperature.

(ii) All measurable properties of the system remain constant.

(iii) All the physical processes stop at equilibrium.

(iv) The opposing processes occur at the same rate and there is dynamic but stable condition.

Which of the following is not a general characteristic of equilibria involving physical processes?

(i) Equilibrium is possible only in a closed system at a given temperature.

(ii) All measurable properties of the system remain constant.

(iii) All the physical processes stop at equilibrium.

(iv) The opposing processes occur at the same rate and there is dynamic but stable condition.

For the reaction H₂(g) + I₂(g) ⇌ 2HI (g), the standard free energy is ∆Gᶱ > 0. The equilibrium constant (K ) would be __________.

(i) K = 0

(ii) K > 1

(iii) K = 1

(iv) K < 1