Pellets of KOH (molar mass = 56.11 g mol−1) are commonly sold as drain cleaner. A safety engineer investigates the thermal hazard associated with dropping 4.80 g of KOH pellets into 200.0 g of water contained in a simple calorimeter whose heat capacity is known to be 125 J °C−1. The water is initially at 21.0 °C. Rapid stirring ensures uniform temperature, and after dissolution is complete the final temperature is 28.4 °C. The specific heat capacity of the solution may be taken as that of pure water.
(a) Calculate the heat absorbed or released by the water.
(b) Calculate the heat absorbed by the calorimeter itself.
(c) Determine the total enthalpy change for the dissolution process of the KOH sample. State the sign clearly.
(d) Calculate the molar enthalpy of dissolution of KOH based on the data.
(e) Classify the dissolution of KOH as exothermic or endothermic and briefly explain how the experimental evidence supports your classification.