Q54. The heat of solution of anhydrous $\mathrm { CuSO } _ { 4 }$ and $\mathrm { CuSO } _ { 4 } \cdot 5 \mathrm { H } _ { 2 } \mathrm { O }$ are $- 70 \mathrm {~kJ} \mathrm {~mol} ^ { - 1 }$ and $+ 12 \mathrm {~kJ} \mathrm {~mol} ^ { - 1 }$ respectively. The heat of hydration of $\mathrm { CuSO } _ { 4 }$ to $\mathrm { CuSO } _ { 4 } \cdot 5 \mathrm { H } _ { 2 } \mathrm { O }$ is $- x \mathrm {~kJ}$. The value of $x$ is $\_\_\_\_$ (nearest integer).