A cylinder with fixed capacity 67.2 lit contains helium gas at STP.

The amount of heat needed to raise the temperature of the gas by

20^{\circ}C is : [ Given that R=8.31J\: mol^{-1}\: K^{-1}]

  • Option 1)

    350 J

  • Option 2)

    374 J 

  • Option 3)

    748 J

  • Option 4)

    700 J

 

Answers (1)

 

Specific heat for isochoric process -

C_{V}= \frac{f}{2}R

C_{p}-C_{v}=R

 

- wherein

f is degree of freedom

 

 

1 mole at STP \rightarrow 22.4 lt

So, 67.2 lt \rightarrow \frac{67.2}{22.4} mole

and cylinder is with fixed capacity

So volume is constant means isochoric process

Q=n C_V\Delta t=n(\frac{3R}{2})\Delta t

                          =(\frac{67.2}{22.4})\times \frac{3}{2}\times 8.314\times 20

\Delta Q=748J


Option 1)

350 J

Option 2)

374 J 

Option 3)

748 J

Option 4)

700 J

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