## Changes in pressure

Volume: $\Delta S = nR\ln \frac{V_{2}}{V_{1}}$
Temperature: $\Delta S = nC\ln \frac{T_{2}}{T_{1}}$

Riya Sood 4G
Posts: 160
Joined: Sat Aug 24, 2019 12:18 am

### Changes in pressure

4H.1 Which substance in each of the following pairs has the
higher molar entropy at 298 K: (a) HBr(g) or HF(g); (b) NH3(g) or
Ne(g); (c) I2(s) or I2(l); (d) 1.0 mol Ar(g) at 1.00 atm or 1.0 mol
Ar(g) at 2.00 atm?

For part (d), why does a lower pressure result in a higher entropy? The answer key stated that 1.0 mol of Ar(g) at 1.00 atm has higher molar entropy.

Posts: 103
Joined: Sat Aug 24, 2019 12:15 am

### Re: Changes in pressure

Entropy is a measurement of how much disorder there is in a system. If you think of increasing pressure as decreasing the volume, there is less available space for atoms to be disorderly. Because of this, there is less entropy, so a higher pressure will give a smaller entropy.

Giselle Littleton 1F
Posts: 78
Joined: Wed Sep 18, 2019 12:20 am

### Re: Changes in pressure

Lower pressure leads to an increase in positional disorder of the atoms as a gas is compressed.