Question

4.

Calculate ΔS∘ at 25 ∘C for each of the following reactions. Suggest a reason for the sign of ΔS∘ in each case. For all, use four significant figures.

Part A

2S(s)+3O2(g)→2SO3(g)

Part C

SO3(g)+H2O(l)→H2SO4(aq)

Part E

AgCl(s)→Ag+(aq)+Cl−(aq)

Part G

NH4NO3(s)→N2O(g)+2H2O(g)

Answer 1

Part A

2S(s)+3O2(g)→2SO3(g)

ΔS∘   = S⁰ f rpoducts - S⁰ f reactants

        = 2*256.7-(31.9+3*205.1)   = -133.8J/mole-K

Part C

SO3(g)+H2O(l)→H2SO4(aq)

ΔS∘   = S⁰ f rpoducts - S⁰ f reactants

         = 156.9-(256.7+69.9)   = -169.7J/mole-K

Part E

AgCl(s)→Ag+(aq)+Cl−(aq)

ΔS∘   = S⁰ f rpoducts - S⁰ f reactants

          = 72.7+56.5-(96.3)   = 32.90J/mole-K

Part G

NH4NO3(s)→N2O(g)+2H2O(g)

ΔS∘   = S⁰ f rpoducts - S⁰ f reactants

        = 2*188.7+219.7-(151.1)    = 446.1J/mole-K