Question

A person adds $1.71$ grams of sugar $\left(C_{12}{H}_{22}{O}_{11}\right)$ in order to sweeten his tea. The number of carbon atoms added is (Mol. mass of sugar = $342$) :

• A. $3.6\times {10}^{22}$
• B. $7.2\times {10}^{21}$
• C. $0.05$
• D. $6.6\times {10}^{22}$

Answer 1

The correct option is A $3.6\times {10}^{22}$

The number of moles is the ratio of mass to molar mass.
Moles of Sugar = $\frac{1.71}{342}=\frac{1}{200}mol$

The number of molecules is the product of the number of moles and Avogadro's number $N_A=6.023\times {10}^{23}$.

Number of molecules = $\frac{1}{200}\times N_A$
Number of C atoms = $12\times \frac{1}{200}\times N_A=3.6\times {10}^{22}$