Question

Explain the increase in pressure of a gas when its volume is decreased at a constant temperature.

Answer 1

According to combined gas law:

$$\frac{p_1V_1}{T_1}=\frac{p_2V_2}{T_2},\\\space\\ T_1=T_2,\\\space\\ p_1V_1=p_2V_2,\\\space\\ p_2=p_1\frac{V_1}{V_2}.$$

The volume is decreased, which means that

$$V_2<V_1,\rightarrow\frac{V_1}{V_2}>1,$$

so, the pressure increases.