Question

7. (30pts) The reaction 2A → Bau + C is an endothermic reaction used in instant cold-packs, with a standard enthalpy of 25.7% and a standard entropy of 95 ... If 6 moles of reactant A are used to cool 1L of water initially at a temperature of 25°C, show that the system coming to equilibrium is a spontaneous process. Assume the reaction goes to completion. The density of water is 14 and the specific heat of water is 4.2

Answer 1

Standard enthalpy change = 25.7 kJ/mol

Standard entropy change = 95 J/mol.K = 0.095 kJ/mol.K

Temperature = 25 degree C = 298 K

For a reaction to be spontaneous, change in Gibbs energy must be negative.

For mular for change in Gibbs energy is,

$\Delta$G = $\Delta$ H - T$\Delta$S

$\Delta$G = 25.7 - 298 ( 0.095 )

$\Delta$G = - 2.61 kJ/mol

Since change in Gibbs energy is negative, the reaction is spontaneous.