One mole each of He and A(g) are taken in a 10 L closed flask and heated to 400 K to establish the following equilibrium. A(g) B(g) Kc for this reaction at 400 K is 4.0. The partial pressures (in atm) of He and B(g) are respectively (at equilibrium) (Assume He, A(g) and B(g) behave as ideal gases) (Given : R = 0.082 L atm K-1 mol-1)
- 3.28, 2.624
- 2.624, 3.28
- 3.28, 0.656
- 0.656, 6.56
Answer
(1) 3.28, 2.624
Solution
He does not react; it only exerts its own partial pressure.
A(g) B(g)
Initial (mol): 1, 0
At equilibrium (mol): 1 − a, a
Kc = [B][A] = a/10(1-a)/10 = 4
⇒ a = 4 − 4a ⇒ a = 0.8 mol
Partial pressure, p = nRTV
pHe = 1 0.082 40010 = 3.28 atm
pB = 0.8 0.082 40010 = 2.624 atm
∴ 3.28 atm and 2.624 atm
Answer: (1)