Question

A man writes his biodata with carbon pencil on the plane paper having mass 150 mg. After writing his biodata, he weighs the written paper and find its mass 152 mg. What is the number of carbon atoms present in the paper?

• A. $1.0036\times {10}^{20}$
• B. $5.02\times {10}^{20}$
• C. $1.0036\times {10}^{23}$
• D. $0.502\times {10}^{20}$

Answer 1

Answer: (A)

$1.0036\times {10}^{20}$

Mass of C-atoms $=152-150=2$ mg

Molar mass of C-atoms $=12g=12000$ mg

12000 mg of carbon contains $6.022\times {10}^{23}$ atoms carbon

$\therefore$ 2 mg of carbon contains $=\frac{6.022\times {10}^{23}}{12000}\times 2$

$=0.0010036\times {10}^{23}$

$=1.0036\times {10}^{20}$ atoms

Therefore, option A is correct.