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Q.
In a mixture of $1\, g\, H _{2}$ and $8\, g\, O _{2}$ the mole fraction of hydrogen is
ManipalManipal 2019
Solution:
Number of moles of hydrogen
$\left(H_{2}\right)=\frac{\text { Weight in gram of } H_{2}}{\text { Molecular weight of } H_{2}}$
Weight of $H_{2}$ in gram $=1\, g$
molecular weight of $H _{2}=2$
Number of moles of $H_{2}=\frac{1}{2}=0.5$ moles
Number of moles of $\left(O_{2}\right)=\frac{\text { Weight in gram of } O_{2}}{\text { Molecular weight of } O_{2}}$
$=\frac{8}{32}=0.25$ moles
Mole fraction of $\left(H_{2}\right)=\frac{\text { Number of moles of } H_{2}}{\text { Total number of moles }}$
$=\frac{0.5}{0.25+0.5}=0.667$