A container has two chambers of volumes V1=2 litres and V2=3 litres separated by a partition made of a thermal insulator. The cha…

Question

A container has two chambers of volumes V1=2 litres and V2=3 litres separated by a partition made of a thermal insulator. The chambers contain n1=5 and n2=4 moles of ideal gas at pressures p1=1 atm and p2=2 atm, respectively. When the partition is removed, the mixture attains an equilibrium pressure of:

1. A. 1.3 atm
2. B. 1.6 atm (Correct answer)
3. C. 1.4 atm
4. D. 1.8 atm

Correct Answer

Option B — 1.6 atm

Detailed Solution & Explanation

The correct answer is 1.6 atm.

Key Points

• The internal energy (and hence $pV$) is conserved on mixing at the same temperature: $p_1V_1+p_2V_2=p\,(V_1+V_2)$.
• $1(2)+2(3)=p(2+3)\Rightarrow 8=5p$.
• $p=\dfrac{8}{5}=1.6$ atm.