A 0.300 M solution of KOH at 25 °C is prepared in the laboratory
CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
A 0.300 M solution of KOH at 25 °C is prepared in the laboratory. A student takes 40.0 mL of this solution and dilutes it with distilled water to a final volume of 750.0 mL. The resulting solution is stored overnight in a warm lab where the temperature rises to 50 °C. The ion-product constant of water at 50 °C is Kw=5.50×10−14, corresponding to pKw=13.26.
(a) Calculate [OH−] immediately after the dilution is completed, while the solution is still at 25 °C.
(b) Determine the pOH and pH at 25 °C for the diluted solution.
(c) Assuming no KOH is lost, calculate the pOH and pH of the same solution after it equilibrates to 50 °C.
(d) Explain, with reference to Kw, why the numerical value of a neutral pH differs at 50 °C compared with 25 °C, and evaluate whether the diluted KOH solution could ever be classified as neutral under the warmer conditions.