It takes 26 s for 10 mL of H2 to effuse through a porous membrane. It takes 130 s for 10 mL of an unknown gas to effuse. Hence, molecular weight of the unknown gas is (in gmol−1 )
50
rH2=1026 mLs−1
rx=10130 mLs−1
rH2rx=102610130=√mxmH2=√mx2
5=√mx2
∴mx=50 gmol−1