A Vessel contains 14g of hydrogen and 96g if oxygen at STP. (a) Find the colume of the vessel. (b) Chemical reaction is induced bu passing electric spark in the vessel till one of the gases is consumed, The temperature is brought back to its starting value 273K. Find the pressure in the vessel.

Explanation

(a) The number of moles of hydrogen `=(14g)/(2g)=7` and the number of moles of oxygen `=(96g)/(32g)=3`. The total number of moles in the vessel `=7+3=10`. The pressure is `1 atm =1.0xx10^(5)N m^(-2)`and the temperature=273K.
Now pV=nRT …(i)
or,`
=0.23m^(3).`
(b)when electric spark is passed, hydrogen reacts with oxygen to from water `(H_(2)O)`. Each gram of hydrogen reacts with eight grams of oxygen. Thus, 96g of oxygen will be totally consuned together with 12g of hydrogen, The gas left in the vessel will be 2kg of hydrogen which is n'=1 mole.
Neglecting the volume of the water formed,
`p'V=n'RT`. ...(ii)
Fron (i)and (ii),
`(p')/(p)=(n')/(n)=(1)/(10)`
or,`p'=pxx0.10
`=0.10atm`.