Respuesta :
Answer:
Molecular mass of unknown gas is 87.58 grams per mol.
Explanation:
Let x be the molecular mass of the unknown gas.
Rate of effusion of a gas and its molecular mass is related as:
r ∝ [tex]\frac{1}{\sqrt{M} }[/tex]
where r is rate and M is molecular mass.
Molecular mass of He gas = 4 g/mol
Given: Same amount of gas is effused and at same conditions.
Let us say V mL of gas effused.
Then rate = V/t where t is time taken for effusion.
[tex]t_{He}=53\ s\\t_{unknown\ gas}=248\ s[/tex]
[tex]r=\frac{V}{t}=\frac{k}{\sqrt{M} }[/tex]
Since same amount of gases are effused V doesn't matter.
We can say:
t ∝ √M ⇒
then
[tex]\frac{53}{248}=\frac{\sqrt{4} }{\sqrt{x} }\\x=87.58\ g\ per\ mol[/tex]
Hence molecular mass of unknown gas is 87.58 grams per mol.
