The rate of effusion of oxygen to an unknown gas is 1.49. what is the other gas?

Answer is: the other gas is chlorine (Cl ₂).

rate of effusion of oxygen : rate of effusion of gas = 1.49 : 1.

rate of effusion of oxygen = 1/√M (O ₂).

rate of effusion of oxygen = 1/√32.

rate of effusion of oxygen = 0.176.

rate of effusion of gas = 1/√M (gas).

rate of effusion of oxygen = rate of effusion of gas · 1.49.

1/√M (gas) = 0.176 1.49

1 / √M (gas) = 0.118.

√M (gas) = 1 : 0.118 = 8.46.

M (gas) = 8.46² = 71.5.