Question

Pressure versus temperature graph of an ideal gas at constant volume is a straight line ‘A’ as shown in Fig. The mass of the gas is doubled and volume is halved. The corresponding pressure vs temperature graph is given by

(1) A

(2) B

(3) C

(4) None of the above

Answer 1

(2) B

For an ideal gas

PV = nRT

where n = number of moles. For mass m of gas having molar mass

M ; n = m/M. Therefore

Obviously at constant volume P–T graph is a straight line having a slope = mR/MV. When m is doubled and volume is halved the slope of P vs T becomes 4 times its earlier value i.e. increases.