Question

To prevent the presence of air, noble gases are placed over highly reactive chemicals to act as inert "blanketing" gases. A chemical engineer places a mixture of noble gases consisting of 5.78 g of He, 15.1 g of Ne, and 34.5 g of Kr in a piston-cylinder assembly at STP. Calculate the partial pressure of each gas

PHe =   atm PNe =   atm PKr =   atm

Answer 1

no of mole of a gas = w/Mwt

He = 5.78/4 , Ne = 15.1/20 , Kr = 34.5/83.8

total no of mole of mixer (ntotal) = (5.78/4)+(15.1/20)+(34.5/83.8) = 3.158 mole

molefraction of He = nHe/nTotal = (5.78/4)/3.158 = 0.46

molefraction of Ne = nNe/nTotal = (15.1/20)/3.158 = 0.24

molefraction of Kr = 1-(0.46+0.24) = 0.3

partial pressure of He(pHe) = xHe*Ptotal

Ptotal = 1 atm (at STP)

  pHe = 0.46*1 = 0.46 atm

pNe = 0.24*1 = 0.24 atm

pKr = 0.3*1 = 0.3 atm