Q.Argon is an inert gas used in light bulbs to retard the vaporization of the tungsten filament. A certain light bulb containing argon at 1.2 atm and 18$^\circ$C is heated to 85$^\circ$C at constant volume. Calculate its final pressure in atm.

Gay-Lussac's law states that, at constant volume, the pressure of a fixed mass of gas is directly proportional to its Kelvin temperature:

Lines of constant volume on a pressure-vs-temperature graph are called isochores; a class activity confirms the law directly by recording the pressure of 1 mole of gas at six temperatures in two differently sized (but each individually fixed) containers, and finding pressure rises linearly with Kelvin temperature in both. …