Question

Chlorophyll, the green colouring matter of plants contains $2.68\%$ magnesium by weight. Calculate the number of magnesium atoms in $3.00g$ of chlorophyll. (atomic mass of $Mg=24$)

Answer 1

Weight of $Mg$ in 3.00 g of Chlorophyll is $\frac{3\times 2.68}{100}$ = 0.0804 g

No of moles of $Mg$ = $\frac{0.0804}{24}$

No. of atoms present in $Mg$ = $\frac{0.0804}{24}\times 6.023\times {10}^{23}$ = $2.01\times {10}^{21}$ atoms of $Mg$