Kw and pH of basesEdexcel A-Level Chemistry: Flashcards

Exam questions on Kw and pH of bases

1. A technician prepares a 0.0250 mol dm⁻³ solution of sodium hydroxide, a strong base, for a cleaning product. All measurements are at 298 K, where the ionic product of water, $K_w$, is 1.00 × 10⁻¹⁴ mol² dm⁻⁶.
   Calculate the pH of the sodium hydroxide solution.2 marks
2. A water-treatment plant dissolves barium hydroxide, Ba(OH)₂, a strong base, to make a 0.0150 mol dm⁻³ solution at 298 K, where $K_w$ = 1.00 × 10⁻¹⁴ mol² dm⁻⁶.
   Calculate the pH of the barium hydroxide solution.2 marks
3. The ionic product of water varies with temperature. At 298 K, $K_w$ = 1.00 × 10⁻¹⁴ mol² dm⁻⁶. At 323 K (50 °C), $K_w$ = 5.48 × 10⁻¹⁴ mol² dm⁻⁶. A student measures the pH of pure water at 323 K with a calibrated meter.
   Calculate the pH of pure water at 323 K.3 marks