Question

Gibbs Helmholtz equation relates the enthalpy, entropy and free energy change of the process at constant pressure and temperature as
`DeltaG=DeltaH-TDeltaS " (at constant P, T)"`
In General the magnitude of `DeltaH` does not change much with the change in temperature but the terms `TDeltaS` changes appreciably. Hence in some process spontaneity is very much dependent on temperature and such processes are generally known as entropy driven process.
The Dissolution of `CaCl_(2).6H_(2)O` in a large volume of water is endothermic to the extent of 3.5 kcal `"mol"^(-1)` and `DeltaH` for the reaction is -23.2 kcal `"mol"^(-1)`.
`CaCl_(2)(s)+6H_(2)O(l)rarrCaCl_(2).6H_(2)O(s)`
Select the correct statement :
A. `DeltaH_("solution")` for anhydrous `CaCl_(2)` is - 19.7 kcal/mol and the process is enthalpy driven
B. `DeltaH_("solution")` for anhydrous `CaCl_(2)` is - 19.7 kcal/mol and the process is entropy driven
C. Dissolution of `CaCl_(2).6H_(2)O` in water is enthalpy driven process
D. The `Delta_(r )S` the reaction `CaCl_(2)(s)+6H_(2)O(l)rarrCaCl_(2).6H_(2)O(s)` is negative

Answer 1

Correct Answer - A
`CaCl_(2)(s)+aq+6H_(2)OrarrCaCl_(2)(aq)+x`
`CaCl_(2)(aq)rarrCaCl_(2).6H_(2)O(s)+aq+3.5`
`CaCl_(2)(s)+6H_(2)OrarrCaCl_(2).6H_(2)O(s)+x+3.5`
`x+3.5 =23.2`
`x = 19.7`
`DeltaH=-x=-19.7`
enthalpy driven