For the Reaction: NaCl (aq) + AgNO3 (aq) → NaNO3 (s) + AgCl(s)

Question

For the Reaction: NaCl (aq) + AgNO3 (aq) → NaNO3 (s) + AgCl(s) 

a. Will the reaction occur spontaneously at room temperature?

b. Do you predict that the reaction will be endothermic or exothermic? Justify your prediction.

Answer 1

a. The reaction does occur spontaneously as the AgCl precipitates thereby removing Ag⁺ and Cl^- ions from solution and driving the reaction to the right.

b. The reaction is exothermic. In a spontaneous reaction the Gibb's free energy change is negative, but the entropy change is negative as a less disordered system is produced. The equation is ΔG = ΔH - TΔS . As ΔS is negative, the product TΔS must be positive. However, as we know the reaction is spontaneous, ΔG must be negative, so ΔH must negative also; otherwise, ΔG could not be negative. Exothermic reactions have a negative ΔH.