Question

The stopcock containing two bulbs of volume $5litre$ and $10litre$ containing an ideal gas at $9atm$ and $60$ atm respectively is opened. What is the final pressure in atm if the temperature remains the same?

Answer 1

Total volume $=5L+10L=15L$
Number of moles in 5 L bulb $n=\frac{PV}{RT}=\frac{9atm\times 5L}{RT}=\frac{45}{RT}moles$
Number of moles in 10 L bulb $n^{\prime }=\frac{PV}{RT}=\frac{60atm\times 10L}{RT}=\frac{600}{RT}moles$
Total number of moles $n"=n+n^{\prime }=\frac{45}{RT}+\frac{600}{RT}=\frac{645}{RT}$
The final pressure $P=\frac{n"RT}{V}=\frac{645RTRT}{15}=43atm$