Chemistry Practice Problems Entropy Practice Problems Solution: For each pair of substances, at the same temperatu...

Solution: For each pair of substances, at the same temperature, choose the one with the higher entropy:I. (i) I2(l) (ii) I2(s)II. (i) PCl3(g) (ii) PCl5(g)III. (i) BaI2(aq) (ii) BaI2(s)IV. (i) 2 moles of NO2(g) (ii) 1 mole of N2O4(g)a. (ii) (i) (i) (i)b. (i) (ii) (i) (ii)c. (i) (i) (ii) (i)d. (ii) (ii) (i) (i)e. (i) (ii) (i) (i)

Problem

For each pair of substances, at the same temperature, choose the one with the higher entropy:

I. (i) I2(l) (ii) I2(s)

II. (i) PCl3(g) (ii) PCl5(g)

III. (i) BaI2(aq) (ii) BaI2(s)

IV. (i) 2 moles of NO2(g) (ii) 1 mole of N2O4(g)

a. (ii) (i) (i) (i)

b. (i) (ii) (i) (ii)

c. (i) (i) (ii) (i)

d. (ii) (ii) (i) (i)

e. (i) (ii) (i) (i)

Solution

We’re being asked to predict which has the greatest entropy (ΔS) for the given reactions. Recall that if:

• ΔS > 0 or ΔS = (+); entropy is increased

• ΔS < 0 or ΔS = (–); entropy is decreased


Remember that phase changes lead to a change in entropy:

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