Question

Study the figure given below and mark the correct expression.

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

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

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, $\Delta H _{\text {soln }}^{0}=\Delta H _{\text {lattiace }}^{0}+\Delta H _{\text {hyd }}^{0}$