Question

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

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

Answer 1

Answer: (D)

$0.502\times {10}^{20}$

$1\text{mg}=1\times {10}^{-3}\text{g}$

The number of carbon atoms present in the signature $=\frac{1\times {10}^{-3}\text{g}}{12\text{g/mol}}\times 6.023\times {10}^{23}\text{atoms/mol}=0.502\times {10}^{20}\text{atoms}$

Hence the correct option is D.