## 9.35 number of moles question [ENDORSED]

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

Grace Ramey 2K
Posts: 57
Joined: Thu Jul 27, 2017 3:01 am

### 9.35 number of moles question

9.35
Container A is fi lled with 1.0 mol of the atoms of an ideal monatomic gas. Container B has 1.0 mol of atoms bound together as diatomic molecules that are not vibrationally active. Container C has 1.0 mol of atoms bound together as diatomic molecules that are vibrationally active. The containers all start at Ti and the temperature is increased to Tf. Rank the containers in order of increasing change in entropy. Explain your reasoning.

Can someone clarify why in some cases 0.5 mol is used in the delta S = nC(ln(T2/T1)) for n? Why is .5 moles used when the question says each gas has 1 mol of atoms?

Matthew Lin 2C
Posts: 30
Joined: Fri Sep 29, 2017 7:06 am

### Re: 9.35 number of moles question  [ENDORSED]

Containers B and C have diatomic molecules. The problem states that these containers have one mole of ATOMs, and since it takes two atoms to create one diatomic molecule, then you will only have .5 mol of molecules in the containers. Hope that helps!