Q22 / 90 · JEE Main 2021 (27 Aug Shift 2) · Chemistry

Two flasks I and II shown below are connected by a valve of negligible volume.

Figure

When the valve is opened, the final pressure of the system in bar is x×10-2. The value of x is (Integer answer)
[Assume : Ideal gas; 1 bar =105 Pa : Molar mass of N2=28.0 mol-1;R=8.31 J mol-1 K-1

Correct answer: 84

Solution

Applying ; n-I+n-IIinitial =The final number of moles.

n-I and n-II are the number of moles of gas in each container.

⇒ Assuming the system attains a final temperature of T (such that 300<T<60)

⇒∣ Heat lost by N2 of container (I)|=| Heat gained by N2 of container II|}

⇒n-ICm300-T)=n-IICm(T-60)

⇒2.828(300-T)=0.228( T-60)

⇒14(300-T)=T-60

⇒(14×300+60)15=T

⇒T=284 K (final temperature)

⇒ If the final pressure =P

⇒nfinal =3.028

⇒PRTVI+VII=3.0gm28gm/mol

P=328 mol×8.31Jmol-K×284 K3×10-3 m3×105barPa

⇒0.84287bar

⇒84.28×10-2 bar 

⇒84

Hence, the correct answer is 84.

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