Question

Study the figure given below and mark the correct expression.

The enthalpy of solution of $X{Y}_{(s)}$, $\Delta H_{soln.}^{°}$ in water can be determined by

• A. $\Delta H_{lattice}^{\circ }=\Delta H_{hyd}^{\circ }+\Delta H_{soln.}^{\circ }$
• B. $\Delta H_{hyd}^{\circ }=\Delta H_{lattice}^{\circ }+\Delta H_{soln.}^{\circ }$
• C. $\Delta H_{soln.}^{\circ }=\Delta H_{lattice}^{\circ }+\Delta H_{hyd}^{\circ }$
• D. $\Delta H_{soln.}^{\circ }=\Delta H_{lattice}^{\circ }\times \Delta H_{hyd}^{\circ }$

Answer 1

Answer: (C)

Hess's Law of Constant Heat Summation (or just Hess's Law) states that regardless of the multiple stages or steps of a reaction, the total enthalpy change for the reaction is the sum of Enthalpy changes of all changes.
So, $\Delta H_{\text{soln }}^0=\Delta H_{\text{lattiace }}^0+\Delta H_{\text{hyd }}^0$