Question

a closed vessel contains equal number of nitrogen and oxygen molecules at pressure of P mm of Hg. if nitrogen is removed from system , then pressure will be

Answer 1

Equal no. of molecules means that the no. of moles of both the compounds are equal.   Hence the mole fraction of each of the component of the mixture is 1/2.   Partial pressure = 1/2 Total pressure.   Now since N2 is removed the total pressure would be equal to the partial pressure exerted by the O2 gas and vice versa.   Therefore, the pressure after the N2 of any gas would be equal to P/2 mm of Hg.