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)

Use the information below to answer this question.

A saturated solution of magnesium hydroxide, Mg(OH)₂, contains 0.1166 g of Mg(OH)₂ in 10.00 dm³ of solution. In this solution the magnesium hydroxide is fully dissociated into ions.

Which one of the following is the pH of a solution of magnesium hydroxide containing 4.0 × 10⁻⁵ mol dm⁻³ of hydroxide ions at 298 K?

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

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