Calculate the total pressure in a 10 L cylinder which contains 0.4 g of helium1.6 g of oxygen and 1.4 g of nitrogen at 27°C.  Assume ideal behaviour for gases R = 0.082

no. of mol of He =wt.mol.wt=0.4g4gmol−=0.1molno. of mol of O2=wt.mol.wt.=1.6g32gmol−=0.05molno. of mol of N2=wt.mol.wt.=1.4g28gmol−=0.05molTotal no. of mol =0.1+0.05+0.05=0.2T=27+273=300KTotal pressureP=nRTV=0.2mol×0.0821LatmK−mol−×300K10L=0.492atm.