Question

If mass percentage of $M{g}^{2+}$ in a biomolecule is 0.2%, then the number of $M{g}^{2+}$ ions present in 10 g of biomolecule is (Atomic weight of Mg = 24)

• A. $\frac{1}{2}\times {10}^{-2}{N}_A$
• B. $\frac{1}{12}\times {10}^{-2}{N}_A$
• C. $\frac{1}{4}{N}_A$
• D. $\frac{1}{12}{N}_A$

Answer 1

The correct option is B $\frac{1}{12}\times {10}^{-2}{N}_A$

$100$% of biomolecule contains-$0.2$% of $M{g}^{2+}$

So, $10g$ of biomolecule contains-$\frac{2}{100\times 10}\times 10$

$\Rightarrow 2\times {10}^{-2}gM{g}^{2+}$

$10g$ of biomolecule contains-$2\times {10}^{-2}gM{g}^{2+}$

$\Rightarrow 24g⟶N_A$

$\Rightarrow 2\times {10}^{-2}g⟶x$

$\Rightarrow x⟶\frac{2\times {10}^{-2}g\times N_A}{24}$

$\Rightarrow x⟶\frac{1}{12}\times {10}^{-2}{N}_A$

The number of $M{g}^{2+}$ ions present in $10g$ of biomolecules is $\frac{1}{12}\times {10}^{-2}{N}_A$.