Question

What is the average molar mass of a gas that is 67.0% H and 33.0% He?

Please answer ASAP!

Answer 1

`=12.08" g/mol"`

Explanation:

1. Assuming that the mass of the compound is 100g; therefore, mass of its constituent elements are:
   `H=100gxx67.0%=67.0g`
   `He=100gxx33.0%=33.0g`
2. Find the relative atomic masses of these elements which are obtainable from the periodic table; i.e.,
   `H=1.01" g/mol"`
   `He=4.00" g/mol"`
3. Now, find the mole value of each element.
   `etaH=(67.0cancel(g))/((1.01cancel(g))/(mol))=66.3mol`
   `etaHe=(33.0cancel(g))/((4.00cancel(g))/(mol))=8.25mol`
4. Then, determine the ratio of moles using the smallest mole value as the denominator.
   `H=66.3/8.25=8`
   `He=8.25/8.25=1`
5. Therefore, the compound is `H_8He` and its molar mass;
   `H=8xx 1.01" g/mol"=8.08" g/mol"`
   `He=1xx4.00" g/mol"ul(=4.00" g/mol"`
   `"Molar mass of " H_8He = 12.08" g/mol"`