Question

Calculate the enthalpy of solution of potassium chloride if its $\Delta_{\text{L}\text{H} = 700 \text{ kJ mol}^{-1}$ and $\Delta_{\text{hyd}} \text{ H} = -680 \text{ kJ mol}^{-1}$

• A. 20 kJ mol$^{-1}$
• B. 345 kJ mol$^{-1}$
• C. 690 kJ mol$^{-1}$
• D. 1380 kJ mol$^{-1}$

Hint:

Enthalpy of solution is the sum of Lattice Enthalpy (always positive) and Hydration Enthalpy (always negative).

Answer 1

The Correct Option is A

Step 1: Formula
$\Delta_{sol}H = \Delta_L H + \Delta_{hyd}H$
Step 2: Calculation
$\Delta_{sol}H = 700 \text{ kJ mol}^{-1} + (-680 \text{ kJ mol}^{-1})$
$\Delta_{sol}H = 700 - 680 = 20 \text{ kJ mol}^{-1}$
Final Answer: (A)