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Calculate the free energy change on diss...

Calculate the free energy change on dissolving one mole of sodium chloride at `25^(@)C.` Lattice energy `=- 777.8 kJ mol^(-1)` hydration energy `=-774 kJ mol^(-1)` of `NaCl, Delta S` at `25 ^(@)C = 0.043 kJ mol ^(-1) K ^(-1).`

Text Solution

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`Delta H _("solution") = Delta H _("lattice") + Delta H _("hydration") = 777.8 kJ mol ^(-1) + (- 774. 1 kJ mol ^(-1))`
`=777. 8 kJ mol ^(-1) - 774. 1 kJ mol ^(-1) = 3.7 kJ mol ^(-1)`
According to Gibbs-Helmholtz equation , `Delta G = Delta H - T Delta S`
`Delta G = 3. 7 kJ mol ^(-1) - ( 273 + 25) K xx 0.043 kJ mol ^(-1) K ^(-1)`
`= 3. 7 kJ mol ^(-1) - 298 xx 0. 043 kJ mol ^(-1) = 3. 7 kJ mol ^(-1) - 12.81 4kJ mol ^(-1) =- 9.114 kJ mol ^(-1)`
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