Question

An unknown gas effuses 0.5 times faster than hydrogen gas (H2). What is the molecular mass of the gas?

1.008 g/mol
4.064 g/mol
2.0 g.mol
8 g/mol

Answer 1

I had done the quiz twice and got this question incorrect twice. While they wouldn't show me the real answer I do know that 1.008 and 2.0 aren't the answer and based on the rating for the answer below it's probably not D. 8 g/mol. So your answer must be B. 4.064.

If my answer helped and was correct please rate it so other people know. If it wasn't or was leave a comment so other people know.

Thanks

Answer 2

Rate of Effusion of Unknown gas = rX = 0.5

Rate of Effusion of Hydrogen = rH = 1

M.mass of Hydrogen = mH = 2 g/mol

M.mass of Unknown gas = mX = ?

Formula used:

rH / rX = √mX / mH

taking square on both sides,

r²H / r²X = mX / mH
Solving for mX,
mX = (r²H ÷ r²X) × mH
Putting values,
mX = [1² ÷ (0.5)²] × 2 g/mol

mX = (1 ÷ 0.25) × 2 g/mol

mX = 4 × 2 g/mol

mX = 8 g/mol

Result:
Molecular Mass of Unknown gas is 8 g/mol.