The heat of solution of anhydrous \( \text{CuSO}_4 \) and \( \text{CuSO}_4 \cdot 5\text{H}_2\text{O} \) are \( -70 \, \text{kJ mol}^{-1} \) and \( +12 \, \text{kJ mol}^{-1} \) respectively.
The heat of hydration of \( \text{CuSO}_4 \) to \( \text{CuSO}_4 \cdot 5\text{H}_2\text{O} \) is \( -x \, \text{kJ} \). The value of \( x \) is ___________. (Nearest integer)
