Acids and Bases

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

The diagram shows a pH curve produced by adding a strong alkali to a weak acid.

Which point on the curve represents a solution that can act as a buffer?

• A

• B

• C

• D

Which indicator should be used in a titration to find the concentration of a solution of methylamine using 0.010 mol dm^–3 hydrochloric acid?

• Thymol blue (pH range 1.2–2.8)

• Bromophenol blue (pH range 3.0–4.6)

• Phenol red (pH range 6.8–8.4)

• Phenolphthalein (pH range 8.3–10.0)

Which amount of sodium hydroxide would react exactly with 7.5 g of a diprotic acid, H₂A (Mr = 150)?

• 50 cm³ of 0.05 mol dm^–3 NaOH(aq)

• 100 cm³ of 0.50 mol dm^–3 NaOH(aq)

• 100 cm³ of 1.0 mol dm^-3 NaOH(aq)

• 100 cm³ of 2.0 mol dm^–3 NaOH(aq)

The table shows the pKa values for two acids.

Which statement is correct?

• Propanoic acid is a stronger acid than butanoic acid.

• The value of K_a for propanoic acid is greater than that for butanoic acid.

• The value of K_a for propanoic acid is 1.35 × 10^–5 mol dm^–3

• The value of K_a for butanoic acid is 6.61 × 10⁴ mol dm^–3