Chapter 17, Problem 120AE

Interpretation Introduction

Interpretation: The enthalpy of solution per mole of solid NaCl needs to be determined, if the lattice energy of $\text{NaCl}$ is -786 kJ/mol and enthalpy of hydration of 1 mole of gaseous ${\text{Na}}^{\text{+}}$ and 1 mole of gaseous ${\text{Cl}}^{-}$ is -783 kJ/mol.

Concept Introduction: A coffee cup calorimeter is the device that is used to measure the amount of heat involved in a chemical or physical process. During any exothermic chemical process, the heat is released so temperature increases whereas during an endothermic chemical, process temperature decreases as the heat is absorbed.

This temperature change can be used along with the specific heat and mass of the solution to calculate the amount of heat involved or released during the process. The heat change and specific heat can be related with the given formula:

  $\text{q = m }\times \text{C }\times \Delta \text{T}$

Here,

• m = mass of substance
• C = specific heat
• $\Delta \text{T}$ = Temperature change