A sample of helium (He) effuses 2.0 times faster than another gas. What is the molar mass of the other gas?

Question

the correct answer is 16g/mol. I just need an explanation. Thank you!

Answer 1

The answer is from using Grahm's Law:

rate of effusion A/rate of effusion B = √(M_B/M_A)

We will let gas A be Helium, and the unknown gas be B. Because we know that the effusion rate of Helium is 2,0 times faster than gas B and the molar mass of Helium can be round to 4 g/mol for this problem , we can write the equation as follows:

2.0 = √(M_B/4.0) Square both side

4.0 = (M_B/4.0) Multiple both sides by 4.0

16.0 g/mol = M_B

Good luck studying chemistry!!