Question

If 'CHEMISTRY' is written by a graphite pencil, it weighs $3.0\times {10}^{-10}g.$ How many carbon atoms are present in it? $N_A=6\times {10}^{23}$

• A. $1.5\times {10}^{13}$
• B. $2.2\times {10}^{15}$
• C. $4.2\times {10}^{-35}$
• D. $2.4\times {10}^{34}$

Answer 1

The correct option is A $1.5\times {10}^{13}$

Molar mass of carbon = $12g/mol$
So number of carbon atoms $=\frac{3.0\times {10}^{-10}}{12}\times 6\times {10}^{23}$
$=1.5\times {10}^{13}$