Hi Aspirant,

The certain gas which will take three times as long to effuse out as helium its molecular mass will be 36u since volume is same so 3/1 will be equal to root square of Mw2/4.On calculating the mass is 36u.This is based on calculations by basic formulas and it generally comes in 3-4 marks in exam.

Hope it helps!!

Dear Candidate,

You have not completed your question. The info provided in this question is not enough to answer your query. So, please post a new question with full info. Only then we can help you.

Hope you understand.