Question

A container has a volume of `4 L` and holds `2 mol` of gas. If the container is expanded such that its new volume is `7 L`, how many moles of gas must be injected into the container to maintain a constant temperature and pressure?

Answer 1

`color(purple)("3.5 moles of gas must be injected into the container.")`

Explanation:

The answer can be calculated by using Avogadro's law:

`v_1/n_1 = v_2/n_2`

The number 1 represents the initial conditions and the number 2 represents the final conditions.

Identify your known and unknown variables:

`color(purple)("Knowns:"`
`v_1`= 4 L
`v_2`= 7 L
`n_1`= 2 mol

`color(blue) ("Unknowns:"`
`n_2`

Rearrange the equation to solve for the final number of moles:

`n_2=(v_2xxn_1)/v_1`

Plug in your given values to obtain the final number of moles:

`n_2=(7 cancelLxx2mol)/(4\cancel"L")` = `3.5 mol`