A `10.0 L` cylinder of oxygen at `4.0 atm` pressure and `17^(@)C` developed a leak. When the leak was repaired, `2.50 atm` of oxygen remained in the cylinder, still at `17^(@)C`. How many moles of gas escaped?

Explanation

In original gas pressure, the number of moles is
`n_(1)=(P_(1)V)/(RT_(1))=(4.00xx10.0)/(0.082xx290)=1.683 mol`
Final moles
`n_(2)=(P_(2)V)/(RT_(2))=(2.50xx10.0 L)/(0.082xx290)=10.0 mol`
Moles escaped `=n_(2)-n_(1)=1.683-1.05=0.63 mol`