Calculate the change in entropy of copper when converted to gas.
Answer 1
In the following equation, mn are the coefficients of the products and reactants in the balanced reaction equation.
∆S° = [Σ mS° products] – [Σ nS° reactants]
To avoid confusion, I omit typing the unit J/(mol•K) in the intermediate steps.
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Calculate the change in entropy of copper when converted to gas.
Cu(s) ⟶ Cu(g)
∆S° = [S° Cu(g)] – [S° Cu(s)]
= (166.4 – 33.2)
= 133.2 J/(mol•K)
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Calculate the entropy change if Br2(l) is converted to Br2(g).
Br₂(l) ⟶ Br₂(g)
∆S° = [S° Br₂(g)] – [S° Br₂(l)]
= (245.5 – 152.2)
= 93.3 J/(mol•K)
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Calculate the change in entropy if Br2(l) is converted into gas atoms of Br.
Br₂(l) ⟶ 2 Br(g)
∆S° = [2 x S° Br(g)] – [S° Br₂(l)]
= [2 x 175.0] – [152.2]
= 197.8 J/(mol•K)