Co(g) effuses at a rate that is times that of cl2(g) under the same conditions.

Answer is: the ratio of the effusion rate is 1.59 : 1.

1) rate of effusion of carbon monoxide gas = 1/√M(CO).  

rate of effusion of carbon monoxide gas = 1/√28.

rate of effusion of carbon monoxide gas = 0.189.  

2) rate of effusion of chlorine = 1/√M(Cl₂).  

rate of effusion of chlorine = 1/√70.9.  

rate of effusion of chlorine = 0.119.  

rate of effusion of carbon monoxide : rate of effusion of chlorine =

= 0.189 : 0.119 / ÷0.119.

rate of effusion of carbon monoxide : rate of effusion of chlorine = 1.59 : 1.

a is the correct answer