Question

A cylinder with fixed capacity of 67.2 lit contains helium gas at STP. The amount of heat needed to raise the temperature of the gas by 20°C is: [Given that R = 8.31 J mol⁻¹ K⁻¹]
(A) 350 J (B) 700 J
(C) 748 J (D) 374 J

Answer 1

The amount of heat needed to raise the temperature of gas by 20°c is 748J

Given

1.capacity of cylinder is 67.2 litre

R=8.31 J mol⁻¹ K⁻¹

2.Q=nCvΔT

now n=67.2/22.4

He is monoatomic gas

so cv=f/2R=3/2R

Q=67.2/22.4*3/2R*20=748J