A carbon compound contains $12.8 \%$ of carbon, $2.1 \%$ of hydrogen and $85.1 \%$ of bromine. The molecular…

A carbon compound contains $12.8 \%$ of carbon, $2.1 \%$ of hydrogen and $85.1 \%$ of bromine. The molecular weight of the compound is 187.9. Calculate the molecular formula of the compound. (Atomic weight: $\mathrm{H}=1.008, \mathrm{C}=12.0, \mathrm{Br}=79.9$ )
  1. $CH_3Br$
  2. $CH_2Br_2I$
  3. $C_2H_4Br_2$
  4. $C_2H_3Br_3$

Solution


Empirical formula $=\mathrm{CH}_2 \mathrm{Br}$ Empirical formula mass $=12+2+80=94$ Factor, $n=\frac{\text { Molecular mass }}{\text { Empirical formula mass }}$ $=\frac{187.9}{94}=2$ Molecular formula $=\left(\mathrm{CH}_2 \mathrm{Br}ight)_2=\mathrm{C}_2 \mathrm{H}_4 \mathrm{Br}_2$ ~

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