CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
At 40 °C the ion-product constant for water is Kw=2.92×10−14. A solution is prepared by combining 75.0 mL of 0.0500 M HCl(aq) with 25.0 mL of 0.100 M Ba(OH)₂(aq). Both reagents dissociate completely, volumes are additive, and no secondary equilibria need be considered.
(For comparison, at 25 °C the value of Kw is 1.00×10−14.)
(a) Calculate the pH of the resulting solution at 25 °C.
(b) Calculate the pH of the same solution at 40 °C, using the value of Kw provided.
(c) Explain, with reference to the auto-ionization of water, why the pH you obtained in part (b) differs from that in part (a), even though the stoichiometric amounts of acid and base mixed are identical.