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

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.