Acids and Bases A Level

Which one of the following is the change in units of pH which occurs when 10.0 cm³ of a 1.0 M solution of a strong monoprotic acid are made up to 1.0 dm³ with water?

• 1

• 2

• 3

• 5

Addition of which one of the following to 10 cm³ of 1.0 M NaOH would result in the pH being halved?

• 10 cm³ of water

• 100 cm³ of water

• 5 cm³ of 1.0 M HCl

• 10 cm³ of 1.0 M HCl

The pH of 0.001 M NaOH at 25°C is

• 13

• 11

• 9

• 3

An aqueous solution contains 4.0 g of sodium hydroxide in 250 cm³ of solution. (K_w = 1.00 × 10⁻¹⁴ mol² dm⁻⁶) The pH of the solution is

• 13.0

• 13.3

• 13.6

• 13.9

Which one of the following could be true in an aqueous solution of sodium hydroxide?

• [H⁺] = (OH⁻]

• pH = −log₁₀ [OH⁻]

• pH = 1.2

• pH = 12.8

A solution of sodium ethanoate has a pH of 8.91 at 25 °C. The hydrogen ion and hydroxide ion concentrations in this solution are ...

• [H⁺] = 1.00 × 10⁻⁹ mol dm⁻³ [OH⁻] = 1.00 × 10⁻⁵ mol dm⁻³

• [H⁺] = 1.00 × 10⁻⁹ mol dm⁻³ [OH⁻] = 8.13 × 10⁻⁶ mol dm⁻³

• [H⁺] = 1.23 × 10⁻⁹ mol dm⁻³ [OH⁻] = 1.00 × 10⁻⁵ mol dm⁻³

• [H⁺] = 1.23 × 10⁻⁹ mol dm⁻³ [OH⁻] = 8.13 × 10⁻⁶ mol dm⁻³

A weak acid HA dissociates in aqueous solution as shown below

HA(aq) ⇌ H⁺(aq) + A⁻(aq) ∆H = +20 kJ mol⁻¹

Which one of the following changes will result in a decrease in the pH of an aqueous solution of the acid?

• addition of a little aqueous sodium hydroxide solution

• raising the temperature of the solution

• dissolving a little of the sodium salt, NaA, in the solution

• adding a platinum catalyst to the solution

What is the pH of a 0.46 mol dm⁻³ solution of potassium hydroxide at 298 K?

(K_w = 1.0 × 10⁻¹⁴ mol² dm⁻⁶ at 298 K)

• 0.34

• 13.66

• 13.96

• 14.34

What is the pH of a 0.020 mol dm^–3 solution of a diprotic acid which is completely dissociated?

• 1.00

• 1.40

• 1.70

• 4.00

The acid dissociation constant, K_a, of a weak acid HA has the value 2.56 × 10^–4 mol dm^–3.

What is the pH of a 4.25 × 10^–3 mol dm⁻³ solution of HA?

• 5.96

• 3.59

• 2.98

• 2.37