Question

Calculate the molar mass of a gas that diffuses three times faster than oxygen under similar conditions.

Answer 1

rate 3/1= square root of 32/x
square both sides
9/1=32x
x = 32/9
= 3.6
Must be He
molar mass =4

Answer 2

Answer:

Molar mass of unknown gas = 4.0 g/mol

Explanation:

Based on the Graham's law of diffusion, if R1 and R2 are the diffusion rates for gas 1 and gas 2 with respective molar masses M1 and M2, the rates are related as:

$\frac{R1}{R2} = \sqrt{\frac{M2}{M1} }$ -----(1)

If R1 is the rate of diffusion of O2 and R2 that of the unknown gas, then as per the given information

R2 = 3(R1)

Now, molar mass of O2 = M1 = 32 g/mol. Based on eq(1), substituting for R1, M1 we get:

$\frac{1}{3} = \sqrt{\frac{M2}{32} } \\\\M2 = \frac{32}{9} = 3.55 = 4 g/mol$