Question

A container has a volume of `3 L` and holds `7 mol` of gas. If the container is expanded such that its new volume is `15 L`, how many moles of gas must be injected into the container to maintain a constant temperature and pressure?

Answer 1

28 mol

Explanation:

`PtimesV = ntimesRtimesT`

P is pressure
V is volume
n is mol
R is the universal gas constant
T is temperature.

1st situation:
`Ptimes3=7timesRtimesT`

2nd situation
`Ptimes15=ntimesRtimesT`

P is the same in the 1st and 2nd situations. R and T are the same also (n is the moles in the second situation).

`3/15 = 7/n`

`n=(7times15)/3 = 35` moles (total in the second situation. It means there are `35-7 = 28` moles of gas must be injected to have the condition.