A) - 78.2 kJ
B) - 81.2 kJ
C) - 68.2 kJ
D) - 60.1 kJ
Correct Answer: A
Solution :
[a] The required equation is : |
\[CuS{{O}_{4}}\left( S \right)+5{{H}_{2}}O\left( l \right)\to \]\[CuS{{O}_{4}}.5{{H}_{2}}O\left( s \right)\Delta H=?\] |
given that |
\[CuS{{O}_{4}}.5{{H}_{2}}O\left( S \right)+aq.\to CuS{{O}_{4}}.\left( aq \right);\Delta {{H}_{2}}=+11.7kJ\] |
The process of hydration may be expressed as |
\[\underset{\Delta H}{\mathop{CuS{{O}_{4}}}}\,\left( s \right)\xrightarrow{\Delta {{H}_{1}}}\underset{\Delta {{H}_{2}}}{\mathop{CuS{{O}_{4}}\left( aq \right)}}\,\]\[CuS{{O}_{4}}.5{{H}_{2}}O\] |
According to Hess's law |
\[\Delta {{H}_{1}}=\Delta H+\Delta {{H}_{2}}\] |
\[\Delta {{H}_{1}}=\Delta H-\Delta {{H}_{2}}\] |
\[=-\,66.5-11.7\text{ }=-78.2\text{ }kJ\] |
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