If a gas A is 9 times as heavy as hydrogen which will diffuse faster, and by what factor ?

Answer 1

Let's take some volume like 100 cc so rate H2 = 100 cc/100 sec. Then rate gas A = 100 cc/x sec. Mass H2 = 2; mass gas A = 9*2 = 18. The lighter gas, H2, will diffuse faster.
(rate H2/rate A) = sqrt(mm A/mm H2)
(100/100)/(100/x) = sqrt(18/2)
Solve for x = time in seconds for A then determine the ratio.
Post your work if you get stuck.