Question

Chlorophyll is responsible for photosynthesis, that contains $2.68\%$ of magnesium. Calculate the number of magnesium atoms present in $2.00g$ of chlorophyll.

• A. $1.345\times 10^{23} \, atoms \, of \, Mg$
• B. $1.345\times 10^{28} \, atoms \, of \, Mg$
• C. $1.345\times 10^{22} \, atoms \, of \, Mg$
• D. $1.345\times 10^{21} \, atoms \, of \, Mg$

Answer 1

Answer: (D)

$100 \, g$ of chlorophyll contains $2.68 \, g \, Mg=\frac{2 .68}{24}moleMg$ .
$2 \, g$ of chlorophyll contains $\frac{2 .68 \times 2}{24 \times 100}moleMg=2.2\times 10^{- 3} \, mole \, Mg. \, $ $No.ofMg \, atoms \, = \, 2.2 \, \times 10^{- 3} \, \times \, 6.023 \, \times 10^{23} \, \, $
$=1.345\times 10^{21} \, atoms \, of \, Mg$