Question

Calculate the Delta G value from the following data and state whether the process will be spontaneous or non spontaneous at 298K. The heat of reaction is - 85.0 kJ and the entropy change for the reaction is +9.50 J/K.

• A. - 82.2 kJ and non spontaneous
• B. - 87.8 kJ and spontaneous
• C. - 87.8 kJ and non spontaneous
• D. - 2,746 kJ and spontaneous
• E. - 82.2 kJ and spontaneous

Answer 1

The correct option is B - 87.8 kJ and spontaneous

$\Delta H=-85.0kJ=-85.0\times 1000J=-85000J$
$\Delta S=+9.50J/K$
$\Delta G=\Delta H-T\Delta S=-85000-298\times 9.50=-87831kJ=\frac{-87831}{1000}J=-87.8J$
The negative value of the Gibbs free energy change indicates that the reaction is spontaneous.