Question

A sample of He gas requires 1.5 minutes to effuse from a container. How many minutes would it take a sample of CH4 gas to effuse from the same container?

A sample of H2 gas effuses from a container in 12 minutes. An unknown gas requires 48 minutes to effuse under the same conditions. Calculate the molar mass of the unknown gas. The unknown gas consists of only one type of atom and is a significant part of the atmosphere. Identify the gas and write a correct formula.

Answer 1

A)

Apply Effusion law:

Rate 1 / Rate 2 = sqrt(MW2/MW1)

for time, recall that

Rate 1 = 1/time 1

Rae 2= 1/time 2

then

Rate 1 / Rate 2 = sqrt(MW2/MW1)

forms

time 2 / time 1 = sqrt(MW2/MW1)

let "1" be He, MW = 4 g/mol and MW CH4 = 16 g/mol

time 2 / 1.5 min = sqrt(16/4)

time 2 = 1.5 * 2 = 3

CH4 will require 3 minutes approx

Q2.

similarly

time 2 / time 1 = sqrt(MW2/MW1)

48 / 12 = sqrt(MW2/2)

solve for MW2

4^2 = Mw2/2

16*2 = MW2

MW = 32 g/mol

if one ty´pe --> MW = X/2 = 32/2 = 16 g/mol

this must be O2(g) oxygen gas