Question

An open flask contains air at $27^?C$, calculate the temperature to which it should be heated such that one third of air measured at final temperature escapes out.

• A. $81^?C$
• B. $127^?C$
• C. $177^?C$
• D. $227^?C$

Answer 1

Answer: (C)

$177^?C$

Answer 2

Let initial number of moles of air at $27^{\circ} C (300 K )= n$ At temperature $T K$, the no. of moles left $= n -\frac{ n }{3}=\frac{2 n }{3}$ At constant pressure and volume, $n _{1} T _{2}= n _{2} T _{2}$ $n \times 300=\frac{2 n }{3} \times T \Rightarrow T =450 K$ or $177^{\circ} C .$