Q16 / 180 · COMEDK 2013 · Chemistry

A signature, written in carbon pencil weighs $1 \mathrm{mg}$. What is the number of carbon atoms present in the signature?

  • A
    $5.02 \times 10^{23}$
  • B
    $5.02 \times 10^{20}$
  • C
    $6.02 \times 10^{20}$
  • Correct answer
    D
    $0.502 \times 10^{20}$

Solution

Number of carbon atoms $$ \begin{aligned} &=\frac{\text { mass }}{\text { molar mass }} \times 6.023 \times 10^{23} \\ &=\frac{10^{-3}}{12} \times 6.023 \times 10^{23} \\ &=5.02 \times 10^{19}=0.502 \times 10^{20} \end{aligned} $$

Hence, the correct answer is option: 'D'.

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