# Applying Avagadro's law: the relationship between moles and volume of a gas

If $\pu{2.4 mol}$ of gas fill a volume of $\pu{175 mL}$, what volume, in mL, will $5.4$ additional moles of gas fill?

This was a quiz question which I got wrong the first attempt, and I think I got it right this time however I would like some confirmation that it is/is not. The unnamed gas is assumed to be ideal. $$\frac{\pu{2.4 mol}}{\pu{175 mL}} = \frac{\pu{7.8 mol}}{X}, \quad \text{or} \quad X = \frac{\pu{7.8 mol} \times \pu{175 mL}}{\pu{2.4 mol}} = \pu{568.75 mL}$$ Is this accurate?

You are correct in your approach and answer. Assuming the gas to be ideal, one can apply Avogadro's Law which states that for an ideal gas $V \propto n$.
This implies $V_1/n_1 = V_2/n_2$.
Using the given values one does obtain the volume as $568.75\ \mathrm{mL}$