The numerical value of the pH at which water is neutral changes with temperature…
CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
The numerical value of the pH at which water is neutral changes with temperature because the ion–product constant Kw is temperature-dependent.
(1) Without performing any calculations, explain qualitatively why raising the temperature of water increases the numerical value of Kw.
(2) At 35∘C, Kw is reported to be 2.09×10−14. Without using numbers, predict whether the pH of neutral water at this temperature is greater than, equal to, or less than 7. Provide a clear conceptual justification.
(3) Two students prepare a solution at 35∘C with the pH value you predicted in part (b). Student 1 claims the solution is acidic because its pH is below 7, while Student 2 claims the solution is neutral. Identify which student is correct and explain why, making explicit reference to the relationship between [H3O+] and [OH−].