if it takes 1.25 min for 0.01 mol of he to effuse , how long will it take for the same amount of ethane ( c2H6) to effuse?

Answer 1

r1/r2 = √m2/m1

1.25 min/.01mol = 125 min/ 1 mol = r1

m1 = 4.00g/1mol

m2 = 30.07g/1mol

125/r2 = √30.07/4.00

125/r2 = √7.52

125/r2 = 2.74

r2 = 125/2.74 = 45.6 min/ 1 mol

For .01 mol to effuse, .456 min/.01 mol

Answer 2

Look at Graham's Law of Effusion

rate gas1/rate gas2 = √MW gas2/√MW gas1

gas 1 = He and MW = 4

gas 2 = ethane and MW = 30

Since the rate of effusion is inversely proportional to the square root of the molecule weight, simply take square root of 30/4 = 2.74.

For 0.01 moles of ethane to effuse, it will take 1.25 min x 2.74 = 3.42 minutes