A 10 lit vessel contains He gas at 10 atm and TK. How many balloons of one litre capacity at 1 atm and 2TK can be filled by using the gas present in the cylinder.

Moles in balloons = $\frac{1\times 1}{\mathrm{R}\left(2\mathrm{T}\right)}$

Moles of gas in cylinder = $\frac{10\times 10}{\mathrm{R}\left(\mathrm{T}\right)}$

Moles of gas in cylinder = $\frac{10\times 1}{\mathrm{R}\left(\mathrm{T}\right)}$

$\therefore$Moles transfered = $\frac{100}{\mathrm{RT}}-\frac{10}{\mathrm{RT}}=\frac{90}{\mathrm{RT}}$

$1\stackrel{ }{\to }\frac{0.5}{\mathrm{RT}};?\stackrel{ }{\to }\frac{90}{\mathrm{RT}}$

$\Rightarrow \mathrm{no}.\mathrm{of}\mathrm{balloons}=\frac{90/\mathrm{RT}}{0.5/\mathrm{RT}}=180$