# A container has a volume of 4 L and holds 3 mol of gas. If the container is expanded such that its new volume is 8 L, how many moles of gas must be injected into the container to maintain a constant temperature and pressure?

##### 1 Answer
Mar 8, 2017

The number of moles is $= 3 m o l$

#### Explanation:

The Ideal Gas Law is

$P V = n R T$

$\frac{V}{n} = R \frac{T}{P}$

$\frac{V}{n} = k$

Where $k =$constant

${V}_{1} / {n}_{1} = {V}_{2} / {n}_{2}$

${V}_{1} = 4 L$

${n}_{1} = 3 m o l$

${V}_{2} = 8 L$

${n}_{2} = {V}_{2} / {V}_{1} \cdot {n}_{1}$

$= \frac{8}{4} \cdot 3 = 6 m o l$

We must inject $6 - 3 = 3 m o l$