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Question: Answered & Verified by Expert
Natural abundances of ${ }^{12} \mathrm{C}$ and ${ }^{13} \mathrm{C}$ isotopes of carbon are $99 \%$ and $1 \%$, respectively. Assuming they only contributes to the mol. wt. of $\mathrm{C}_{2} \mathrm{F}_{4}$, the percentage of $\mathrm{C}_{2} \mathrm{F}_{4}$ having a molecular mass of $101$ is
ChemistrySome Basic Concepts of ChemistryKVPYKVPY 2013 (SA)
Options:
  • A $1.98$
  • B $98$
  • C $0.198$
  • D $99$
Solution:
2654 Upvotes Verified Answer
The correct answer is: $1.98$
Percentage of $\mathrm{C}_{2} \mathrm{F}_{4}$ of Molar mass $100=\frac{1}{100} \times \frac{1}{100} \times 100=0.01 \%$
Percentage of $\mathrm{C}_{2} \mathrm{F}_{4}$ of Molar mass $102=\frac{99}{100} \times \frac{99}{100} \times 100=98.01 \%$
Percentage of $\mathrm{C}_{2} \mathrm{F}_{4}$ of Molar mass $101=100-(0.01+98.01)=1.98 \%$

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