Question

When $0.2$ mole of anhydrous $CuSO_{4}$ is dissolved in water, the heat evolved is $1.451$ kcal. If $0.2$ mole of $CuSO_{4}.5H_{2}O$ is dissolved in water, the heat absorbed is $0.264$ kcal. Calculate the molar heat of hydration of $CuSO_{4}$.

Answer 1

$ CuSO_{4}\left(s\right) +H_{2}O \to CuSO_{4}\left(aq\right)$
$\Delta H = \frac{-1.451}{0.2} = -7.255 \,k\, cal\, mol^{-1}$
$\left(ii\right) CuSO_{4}. 5H_{2}O\left(s\right) + H_{2}O\to CuSO_{4}\left(aq\right)$
$\Delta H = \frac{0.264}{0.2} = 1.32 \,k\, cal\, mol^{-1}$
From(i)-(ii),
$CuSO_{4}\left(s\right) +5H_{2}O\left(1\right)\to CuSO_{4}.5H_{2}O\left(s\right)$
$\Delta H =-28.575 \,k\, cal\, mol^{-1}$