Question

Two flasks of equal volume are connected by a narrow tube (of negligible volume) all at 27ºC and contain 0.70 mole of H2 at 0.5 atm. One of the flask is then immersed into a bath kept at 127$\underline{o}$ C, while the other remains at 27$\underline{o}$C. The final pressure in each flask is :

• A. Final pressure = 0.5714 atm
• B. Final pressure = 1.5714 atm
• C. Final pressure = 0.5824 atm
• D. None of these

Answer 1

Answer: (A)

Final pressure = 0.5714 atm

Answer 2

Two flask initally at 27⁰ and 0.5 atm, have same volume and 0.7 mole thus each flask has 0.35 mole

Let n mole of gas are diffuse from II to I on heating the flask at 127⁰C

Mole in I flask = 0.35 + n,

Mole in II flask = 0.35 – n

If new pressure of flask is P then

for I flask P × V = (0.35 + n) × R × 300 ;

for II flask P × V = (0.35 – n) × R × 400

n = 0.5

mole in I flask = 0.40 mole in II flask = 0.30

0.5 × 2V = 0.7 × 0.0821 × 300 (initially)

V = 17.24 Lt.

P × 17.24 = 0.30 × 0.0821 × 400 (finally)

P = 0.57 atm.