A gas occupies 3 litres at 0°C. what volume will it occupy at -20°C, assuming pressure remaining constant?

1 Answer
Nov 22, 2017

2.78 litres

Explanation:

If you treat it as an ideal gas, then PV=nRTPV=nRT where P is pressure, V is volume, n is number of moles, R is the gas constant and T is temperature in K.

If you assume pressure is constant, and we know that the amount of substance will remain constant, and of course the gas constant is a constant, then VV varies directly with TT. So for the two temperatures you can say:

V_1.T_1 = V_2.T_2V1.T1=V2.T2
V_2 = (V_1.T_1)/(T_2)V2=V1.T1T2

T_2T2, the higher of the two temperatures, will be 273 K and T_1T1 will be 20 degrees lower, so 253 K.

Now plug in the numbers:

V_2 = (3 . 253)/(273) = 2.78V2=3.253273=2.78 litres.