Question

Two flasks of equal volume are connected by a narrow tube (of negligible volume) all at ${27}^{\circ }\text{C}$ and contains 0.70 mole of $H_2$ at 0.5 atm. One of the flask is then immersed into a bath kept at ${127}^{\circ }\text{C}$, while the other remains at ${27}^{\circ }\text{C}$. 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

The correct option is A Final pressure = 0.5714 atm

Two flasks initially at ${27}^{\circ }\text{C}$ and 0.5 atm, have the same volume and 0.7 mole thus each flask has 0.35 mole.

Let $n$ moles of gas be diffused from II to I on heating the flask at ${127}^{\circ }\text{C}$.

Moles in flask $=0.35+n$, Mole II flask $=0.35-n$
If the new pressure of flask is$P$ then,

From the ideal gas equation,
$PV=nRT$
For I flask $P\times V=(0.35+n)\times R\times 300$;
for II flask $P\times V=(0.35-n)\times R\times 400$
$n=0.5$
mole in flask $=0.40$
mole in II flask $=0.30$
$0.5\times 2V=0.7\times 0.0821\times 300\text{(initially)}V=17.24\text{L}$
$P\times 17.24=0.30\times 0.0821\times \text{(finally)}P=0.57\text{atm}$