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Ch.18 - Free Energy and Thermodynamics
Chapter 18, Problem 33

What is the change in entropy that occurs in the system when 45.0 g of acetone (C3H6O) freezes at its melting point (-94.8 °C)? Use Table 11.9 for the heats of fusion.

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1
Identify the formula for calculating the change in entropy (ΔS) during a phase change: ΔS=qrevT, where qrev is the heat absorbed or released during the phase change and T is the temperature in Kelvin.
Convert the given mass of acetone (45.0 g) to moles using its molar mass (58.08 g/mol).
Use the heat of fusion for acetone from Table 11.9 to calculate qrev. The heat of fusion is the amount of energy required to change a substance from solid to liquid at its melting point.
Convert the temperature from Celsius to Kelvin by adding 273.15 to the given melting point (-94.8 °C).
Substitute the values of qrev and T into the entropy change formula to find ΔS.