Question

hydrogen diffuse seven times faster than gas x under the same pressure calculate the relative molecular mass of gas x if that of hydrogen is 2

Answer 1

Molecular mass of gas x=7×2=14

Answer 2

Nope.

Let rate of X gas diffusion = 1 L/hr, then
rate H2 = 7 L/hr
(rate H2/rate x) = sqrt(molar mass x/molar mass H2)
(7/1) = sqrt (mm x/2)
49 = mm x/2
49 x 2 = molar mass x = 98