Heat and Thermodynamics 6 Question 13

17. Now consider the partition to be free to move without friction so that the pressure of gases in both compartments is the same. Then total work done by the gases till the time they achieve equilibrium will be

(2014 Adv.)

(a) 250R

(b) 200R

(c) 100R

(d) 100R

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Answer:

Correct Answer: 17. (d)

Solution:

  1. ΔW1+ΔU1=ΔQ1(i)

ΔW2+ΔU2=ΔQ2(ii)

ΔQ1+ΔQ2=0

(nCpΔT)1+(nCpΔT)2=0

But n1=n2=2

52R(T700)+72R(T400)=0

Solving, we get T=525K

Now, from Eqs. (i) and (ii), we get

ΔW1+ΔW2=ΔU1ΔU2 as ΔQ1+ΔQ2=0ΔW1+ΔW2=[(nCVΔT)1+(nCVΔT)2]=[2×32R×(525700)+2×52R×(525400)]=100R



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