A student dissolves 4.00 g of (molar mass ) in 100.0 g of water initially at

CHEMISTRY · Multi-part · A Level · Chemistry · Energetics · Energetics

Problem

A student dissolves 4.00 g of KNO3(s)\text{KNO}_3(s) (molar mass 101.1 g mol−1101.1\,\text{g mol}^{-1}) in 100.0 g of water initially at 20.0 ∘C20.0\,^{\circ}\text{C}. The final temperature of the solution is 16.5 ∘C16.5\,^{\circ}\text{C}. Assume the solution’s specific heat capacity is 4.18 J g−1 ∘C−14.18\,\text{J g}^{-1}\,^{\circ}\text{C}^{-1} and heat absorbed by the calorimeter is negligible. (a) Calculate the experimental molar enthalpy of dissolution of KNO3\text{KNO}_3 (in kJ mol−1\text{kJ mol}^{-1}). (b) The literature value is +35.7 kJ mol−1+35.7\,\text{kJ mol}^{-1}. Calculate the percent error of the experimental value. (c) Identify one plausible systematic experimental error that could account for the percent error obtained.

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