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 $
