Answer to Question #331753 in General Chemistry for yow

Question

Determine the spontaneity of the dissociation of ammonium nitrate (NH4NO2), the compound used in

cold packs:

NH4NO3(s) NH4+(aq) + NO3−(aq)

ΔΗ° = 25.7 kJ/mol; AS = 0.108 kJ/K•mol

a. Calculate the AG for the reaction at 25°C.

b. Does the reaction lead to an increase or decrease in the disorder of the system?

c. Is the reaction spontaneous or nonspontaneous at 25°C?

Answer 1

a. ∆G = ∆H - T∆S = 25.7 kJ/mol - (25+273.15 K) × 0.108 kJ/ K mol = -6.5 kJ

b. Reaction leads to an increase in the disorder of the system, because in dissociation reaction one molecule produces a several new molecules.

c. At 25°C ∆G = -6.5 kJ < 0 - reaction spontaneous