Question

The heat evolved during the formation of 24.95 grams of hydrated copper sulphate from anhydrouscopper sulphate (mol.wt=159.5) is :

$CuS{O}_4+5H_{2}O\to CuS{O}_4.5H_{2}O$ $\Delta H=-78.2KJ$

• A. -78.21 KJ
• B. 78.21 KJ
• C. 7.82 KJ
• D. -7.82 KJ

Answer 1

The correct option is D -7.82 KJ

$CuS{O}_4+5H_{2}O\to CuS{O}_4.5H_{2}O$
Moles of hydrated copper sulphate
$=\frac{24.95}{249.5}=\frac{1}{10}$ moles
$\therefore$ heat evolved $=\frac{78.2}{10}kJ=-7.82kJ$

Option D is correct.