Which of the following is the approximate ΔS° for the reaction?

Question

2AgNO₃(aq)+CaBr₂(aq)→2AgBr(s)+Ca(NO₃)₂(aq)

Substance:AgNO₃(aq) Approximate S°  (J/mol K): 220

Substance:CaBr2(aq) Approximate S°  (J/mol K):72

Substance:AgBr(s) Approximate S°  (J/mol K):107

Substance: Ca(NO₃)₂(aq) Approximate S°  (J/mol K):240

The reaction between AgNO₃ and CaBr₂ is represented by the equation above, and the table provides the approximate S° values for the reactants and products. Which of the following is the approximate ΔS° for the reaction?

1. +58 J/Kmol
2. -66 J/Kmol
3. +66 J/Kmol
4. -58 J/Kmol

Answer 1

2AgNO₃(aq) + CaBr₂(aq) ==> 2AgBr(s) + Ca(NO₃)₂(aq)

Products: 2x107 + 240 = 214 + 240 = 454 J/Kmol

Reactants: 2x220 + 72 = 512 J/Kmol

Reaction: products - reactants = 454 - 512 = -58 J/Kmol