Question

8. A gas occupies 3 litres at 0°C. What volume
will it occupy at -20°C, pressure remaining
constant ?
(Ans. 2.78 litres)​

Answer 1

Answer:

If you treat it as an ideal gas, then PV=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 V varies directly with T. So for the two temperatures you can say:

V1.T1=V2.T2

V2=V1.T1T2

T2, the higher of the two temperatures, will be 273 K and T1 will be 20 degrees lower, so 253 K.

Now plug in the numbers:

V2=3.253273=2.78 litres.