Question

Chlorophyll contains 2.68% of $Mg$ by weight. Then the number of $Mg$ atom in 2.00 g of chlorophyll is:

(Atomic mass of $Mg=24$)

Answer 1

Total mass of chlorophyll $=2g$

$\%$ of $Mg$ in chlorophyll $=2.68\%$

$\Rightarrow$ mass of $Mg$ in 2g of chlorophyll $=2\times \frac{2.68}{100}$

Nuumber of magnesium atom $\left(\frac{0.00536}{24}\right)\times (6.023\times {10}^{23})$

$=1.345\times {10}^{20}$ atoms.