# Suppose you were investigating the correlation between intermolecular forces and the way in which molecules cohere to

## Question:

Suppose you were investigating the correlation between intermolecular forces and the way in which molecules cohere to each other in a liquid and decided that you can gain some insight by comparing the entropies of vaporization of several liquids.

Calculate the entropy of vaporization of acetone at 296 K with an external pressure of 1 bar. The molar heat capacity of liquid acetone is 127 J · K^{–1 }· mol^{–1}, its boiling point is 329.4 K, and its enthalpy of vaporization is 29.1 kJ · mol^{–1}.

**PLAN**

**Step 1** Use Eq. 4 to calculate the entropy change accompanying the heating of acetone from the “initial” temperature of 296 K to the “final” temperature of 329.4 K. The heat capacity of liquid acetone is approximately constant over this range.

**Step 2** Use Eq. 5 to calculate the entropy of vaporization or look up the value in Table 4F.1.

**Step 3 **Use Eq. 4 to calculate the entropy change accompanying the cooling of acetone vapor from the new “initial” temperature of 329.4 K back to the new “final” temperature of 296 K (a negative value). The heat capacity of acetone vapor may be estimated from the equipartition theorem (Topic 4B) as C_{P,m} = 4R.

**Step 4** Sum the three entropy changes to give DS_{vap}°(296 K).

What should you assume? Assume that acetone vapor is an ideal gas and that only translations and rotations contribute to the gas-phase heat capacity.

## Step by Step Answer:

**Related Book For**

## Chemical Principles The Quest For Insight

**ISBN:** 9781464183959

7th Edition

**Authors:** Peter Atkins, Loretta Jones, Leroy Laverman