Solve combined gas law relationships.
For a fixed quantity of gas the product of pressure and volume divided by absolute temperature is constant, so PV/T at the first state equals PV/T at the second. Rearranging to isolate the unknown volume gives V2 directly. Reporting the three ratios alongside it shows which effect dominates: raising pressure compresses the gas while raising temperature expands it, and here the compression wins.
Combined gas law solved for volume
P1 V1 / T1 = P2 V2 / T2, so V2 = P1 x V1 x T2 / (T1 x P2)
Yes, and this is the most common mistake. The law relies on temperature being proportional to average kinetic energy, which only holds on an absolute scale. Using celsius produces nonsense, including negative volumes.
Only that they are the same on both sides. Because the law is a ratio, atmospheres and litres, or pascals and cubic metres, both work — the units cancel.
At high pressure and near condensation, where molecular volume and intermolecular attraction matter. Real gases then need a corrected equation of state such as van der Waals.