Question

Chlorophyll contains 2.68% of magnesium by mass. Calculate the number of magnesium atoms in 3.00 gms of chlorophyll.

• A. $\text{2}\text{.01}\times {\text{10}}^{\text{21}}\text{atom}$
• B. $6.023\times {10}^{23}\text{atoms}$
• C. $1.7\times {10}^{20}\text{atoms}$
• D. $2.8\times {10}^{22}\text{atoms}$

Answer 1

The correct option is A $\text{2}\text{.01}\times {\text{10}}^{\text{21}}\text{atom}$

Mass of $Mg$ in $3$ $gm$ chlorophyll $=3\times \frac{2.68}{100}=0.0804$ $gm$

Moles of $Mg=\frac{0.0804}{24}=3.35\times {10}^{-3}$ $moles$

Number of Magnesium atoms $=3.35\times {10}^{-3}\times 6.023\times {10}^{23}=2.01\times {10}^{21}$ $atoms$