Calculate the total pressure in a 10 litre cylinder which contains `0.4g` of helium, `1.6g` of oxygen and `1.4g` of nitrogen at `27^(@)C`. Also calculate the partial pressure of helium gas in the cylinder. Assume ideal behaviour of gases. Given `R = 0.082` litre atm `K^(-1) mol^(-1)`.

Explanation

`"Moles of helium"=(0.4)/(4)=0.1`
`"Moles of oxygen"=(1.6)/(32)=0.05`
`"Moles of nitrogen"=(1.4)/(28)=0.05`
`"Total moles"=0.1+0.5+0.5="0.2 moles"`
`"Volume of gaseous mixture = 10 L"`
`"Temperature"=27+273=300K`
`R="0.082 L atm mol"^(-1)K^(-1)`
`"Now, "pV=nRT`
`"or "p=(nRT)/(V)`
`=(0.2xx0.082xx300)/(10)`
`="0.492 atm."`
Partial pressure of helium = Mole fractiono of `Hexxp`
`=(0.1)/(0.2)xx0.492`
`="0.246 atm."`