Chemical Thermodynamics Question 475

Question: The heat of hydration of solution anhydrous $ CuSO_4 $ and hydrated $ CuSO_4\cdot 5H_2O $ are - 66.5 and 11.7 kJ $ mo{{l}^{-1}} $ respectively. Calculate the heat of hydration of $ CuSO_4 $ to $ CuSO_4\cdot 5H_2O $

Options:

A) - 78.2 kJ

B) - 81.2 kJ

C) - 68.2 kJ

D) - 60.1 kJ

Show Answer

Answer:

Correct Answer: A

Solution:

  • The required equation is : $ CuSO_4( S )+5H_2O( l )\to $

$ CuSO_4.5H_2O( s )\Delta H=- $

given that $ CuSO_4.5H_2O( S )+aq.\to CuSO_4.( aq );\Delta H_2=+11.7kJ $

The process of hydration may be expressed as $ \underset{\Delta H}{\mathop{CuSO_4}},( s )\xrightarrow{\Delta H_1}\underset{\Delta H_2}{\mathop{CuSO_4( aq )}}, $

$ CuSO_4.5H_2O $

According to Hess’s law $ \Delta H_1=\Delta H+\Delta H_2 $

$ \Delta H_1=\Delta H-\Delta H_2 $

$ =-,66.5-11.7=-78.2kJ $



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