$\overline{){\mathbf{\u2206}}{\mathbf{S}}{\mathbf{=}}\frac{\mathbf{\u2206}\mathbf{H}}{\mathbf{T}}}$

ΔS = entropy, J/mol•K

ΔH = enthalpy, J

T = temperature, K

$\overline{){\mathbf{\u2206}}{{\mathbf{S}}}_{{\mathbf{vap}}}{\mathbf{=}}\frac{\mathbf{\u2206}{\mathbf{H}}_{\mathbf{vap}}}{{\mathbf{T}}_{\mathbf{b}}}}$

ΔH_{vap} of acetone = **31.3 kJ/mol** → *convert from kJ to J: 1 kJ = 10 ^{3} J*

T_{b} = 56.1°C + 273.15 =** 329.25 K**

**Calculate ΔS _{vap}:**

$\mathbf{\u2206}{\mathbf{S}}_{\mathbf{vap}}\mathbf{=}\frac{\mathbf{31}\mathbf{.}\mathbf{3}{\displaystyle \frac{\overline{)\mathbf{kJ}}}{\mathbf{mol}}}\mathbf{\times}{\displaystyle \frac{{\mathbf{10}}^{\mathbf{3}}\mathbf{}\mathbf{J}}{\mathbf{1}\mathbf{}\overline{)\mathbf{kJ}}}}}{\mathbf{329}\mathbf{.}\mathbf{25}\mathbf{}\mathbf{K}}\phantom{\rule{0ex}{0ex}}\mathbf{\u2206}{\mathbf{S}}_{\mathbf{vap}}\mathbf{=}\frac{{\displaystyle 31300\frac{J}{\mathrm{mol}}}}{\mathbf{329}\mathbf{.}\mathbf{25}\mathbf{}\mathbf{K}}$

Calculate the change in entropy that occurs in the system when 30.5
g of acetone (C_{3}H_{6}O) vaporizes from a liquid to a gas at its normal boiling point (56.1 ˚C).

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