Name the temperature at which the volume of the gas becomes equal to zero.

The temperature at which the volume of a gas becomes equal to zero is called absolute zero.

If $t=-273^{\circ }C$

Absolute zero ($0K$) = $-273^{\circ }C$

i.e., the volume of gas = $0$; because, before attaining this temperature, molecular motion of the gas is negligible, i.e., they freeze. Gas no longer remains as gas.