Question

An open flask contains air at ${27}^{\circ }C$. Calculate the temperature at which it should be heated so that $1/3rd$ of air measured at ${27}^{\circ }C$ escapes out.

Answer 1

Let the initial number of moles of air at ${27}^{\circ }C\left(300K\right)$ be $=n$

Number of moles of air left when the air is heated to the temperature $T=n-\frac{n}{3}=\frac{2n}{3}$

At constant pressure and constant volume,

$n_1{T}_1=n_2{T}_2$

or $n\times 300=\frac{2n}{3}\times T$

or $T=450K=(450-273)={177}^{\circ }C$.