Question

A flexible container holds `"6.70 mol"` of a gas. An additional `"3.50 mol"` of the gas is added to the container until it reaches a final volume of `"25.4 L"` while temperature and pressure are kept constant, what was the initial volume?

Answer 1

The initial volume was 16.7 L.

Explanation:

This problem requires Avogadro's law, which states that the amount (moles) of a gas is directly proportional to its volume, such that if the amount increases, the volume increases and vice versa. You correctly determined the formula to use: `V_1/n_1=V_2/n_2`

Known
`n_1="6.70 mol"`
`V_2="25.4 L"`
`n_2="6.70 mol+3.50 mol"="10.2 mol"`

Unknown
`V_1`

Solution
Rearrange the equation to isolate `V_1`. Substitute the known values into the equation and solve.

`V_1=(V_2n_1)/n_2`

`V_1=(25.4"L"xx6.70cancel"mol")/(10.2cancel"mol")="16.7 L"` rounded to three significant figures