At \[25{}^\circ C\], when 1 mole of \[MgS{{O}_{4}}\] was dissolved in water, the heat evolved was found to be \[91.2\text{ }kJ.\] One mole of \[MgS{{O}_{4}}\]. \[7{{H}_{2}}O\] on dissolution gives a solution of the same composition accompanied by an absorption of \[13.8\text{ }kJ\]. The enthalpy of hydration, i.e., \[\Delta {{H}_{h}}\] for the reaction \[MgS{{O}_{4}}\left( s \right)+7{{H}_{2}}O\left( l \right)\xrightarrow{{}}MgS{{l}_{4}}.7{{H}_{2}}O\left( s \right)\] is:

At \[25{}^\circ C\], when 1 mole of \[MgS{{O}_{4}}\] was dissolved in

1.	At \[25{}^\circ C\], when 1 mole of \[MgS{{O}_{4}}\] was dissolved in water, the heat evolved was found to be \[91.2\text{ }kJ.\] One mole of \[MgS{{O}_{4}}\]. \[7{{H}_{2}}O\] on dissolution gives a solution of the same composition accompanied by an absorption of \[13.8\text{ }kJ\]. The enthalpy of hydration, i.e., \[\Delta {{H}_{h}}\] for the reaction \[MgS{{O}_{4}}\left( s \right)+7{{H}_{2}}O\left( l \right)\xrightarrow{{}}MgS{{l}_{4}}.7{{H}_{2}}O\left( s \right)\] is:
A.	\[-105\text{ }kJ/mol\]
B.	\[-77.4\text{ }kJ/mol\]
C.	\[105\text{ }kJ/mol\]
D.	None of these
Answer» B. \[-77.4\text{ }kJ/mol\]