Chapter 9, Problem 53E

A coffee cup calorimeter initially contains $\text{125 g}$ water at $\text{24}\text{.2°C}$ . Potassium bromide $\left(\text{10}\text{.5 g}\right)$ , also at $\text{24}\text{.2°C}$ , is added to the water, and after the $\text{KBr}$ dissolves, the final temperature is $\text{21}\text{.1°C}$ . Calculate the enthalpy change for dissolving the salt in $\text{J/g}$ and $\text{kJ/mol}$ . Assume that the specific heat capacity of the solution is $\text{4}\text{.18 J}{\text{°C}}^{\text{-1}}{\text{ g}}^{\text{-1}}$ and that no heat is transferred to the surroundings or to the calorimeter.