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Taking N_(2) and O_(2) as main compounts of air (79% N_(2),21%O_(2) by volume ) what is the molecular mass of air? How has it been arrived at ? |
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Answer» Solution :For a mixture of GASES, the average molecular mass is taken. `"Average molecular mass "=Sigmax_(i)M_(i)=x_(N_(2))M_(N_(2))+x_(O_(2))M_(O_(2))` where `x_(N_(2)) and x_(O_(2))` are mole fractions of `N_(2)` MOLES, therefore, their MOLAR ratio is same as ratio of their volumes. `therefore x_(N_(2))=0.79,x_(O_(2))=0.21.` Also `M_(N_(2))=28u, M_(O_(2))=32U` `therefore"Average molecular mass "=0.79xx28+0.21xx32u=22.12+6.72u=28.84u` |
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