Question

Two flasks of equal volume are connected by a narrow tube (of negligible volume) all at 27⁰ C and contain 0.70 moles of H2 at 0.5 atm. One of the flask is then immersed into a bath kept at 127⁰C, while the other remains at 27⁰ C. The number of moles of H2 in flask 1 and flask 2 are :

• A. Moles in flask 1 = 0.4, Moles in flask 2 = 0.3
• B. Moles in flask 1 = 0.2, Moles in flask 2 = 0.3
• C. Moles in flask 1 = 0.3, Moles in flask 2 = 0.2
• D. Moles in flask 1 = 0.4, Moles in flask 2 = 0.2

Answer 1

Answer: (A)

Moles in flask 1 = 0.4, Moles in flask 2 = 0.3

Answer 2

Let vol. of each flask is 'V' L, Initially

0.5 × 2V = 0.7 × 0.0821 × 300

V = 17.24 L

Let T is final temperature of flask when pressure in each flask becomes equal, it happens. When

nTotal = n1 + n2

$\frac{2}{T} = \frac{1}{400} + \frac{1}{300} = \frac{3 + 4}{1200} = \frac{7}{1200}$

T = $\frac{2400}{7}$ = 342.85 K

P × 2 × 17.24 = n1 × 0.0821 × 400 $\Rightarrow$ n1

= 0.3

0.5714 × 17.24 = n2 × 0.0821 × 300 $\Rightarrow$ n2 = 0.4