Question

one mole of helium is heated from 27°celcius to 327°celcius at constant pressure and constant volume.find the heat exchange and work done.​

Answer 1

As it is a constant pressure process, using Charles law we get

T

V

=constant. Thus for a threefold increase in volume we get threefold increase in temperature. Thus we get the final temperature as 3(273)=819K. Thus ΔT=819−273=546K.

Now as helium is a diatomic molecule, its degree of freedom f is 5. Ths we get C

p

for it as (1+

2

f

)R=(1+

2

5

)R=

2

7

R.

Thus heat transferred will be given as ΔQ=nC

p

ΔT

or

ΔQ=1(

2

7

)(1.987)(546)=3820 cal