Rate of effusion of LPG (a mixture of n-butane and propane) is 1.25 times that of SO3. Hence, mass fraction of n-butane in LPG is
0.75
0.25
0.50
0.67
rLPGrSO3=80M(LPG)=1.25 ∴ 80M=(1.25)2 ∴M(LPG)=51.2 M=M1 (butane) X1+M2 (propane) X2X1+X2 51.2=58X1+441−X11 X1≈0.50