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] `"mol"^(-1) K^(-1)`]

Options

A. `350 J`
B. `374 J`
C. `748 J`
D. `700 J`

Answer

C

Explanation

`Q=nC_v triangleT` (volume is on ts.)
`n=(67.2)/(22A)=3` (as motal volume of a gas at stp =22.4 lit.)
`C_v=(fR)/(2)=(3R)/(2)`
`triangleT=20^(@)`
`Q=3xx(3R)/(2)xx20= 90R=747.9J`.