Question

$2.0g$ of a metallic carbonate on decomposition gave $1.5g.$ of metallic oxide. The equivalent mass of metal is:

• A. $58$
• B. $29$
• C. $5.8$
• D. $2.9$

Answer 1

The correct option is A $58$

Weight of metallic carbonate $=2.0g$

Weight of metallic oxide $=1.5g$

Equivalent weight $=\frac{\text{Weight}}{\text{Valence factor}}$

As the valence factor of both, carbonate and oxide, is 2.

$\therefore$ Equivalent weight of carbonate $=\frac{60}{2}=30$

Equivalent weight of oxide $=\frac{16}{2}=8$

Gram equivalent of metallic carbonate $=\frac{\text{Given weight of carbonate}}{E_{metal}+E_{{C{O}_3}^{-2}}}$

Gram equivalent of metallic oxide $=\frac{\text{Given weight of oxide}}{E_{metal}+E_{O^{-2}}}$

Let the equivalent weight of metal be x.

Gram equivalent of metallic carbonate = Gram equivalent of metallic oxide

$\frac{\text{Given weight of carbonate}}{E_{metal}+E_{{C{O}_3}^{-2}}}=\frac{\text{Given weight of oxide}}{E_{metal}+E_{O^{-2}}}$

$\Rightarrow \frac{2}{x+30}=\frac{1.5}{x+8}$

$\Rightarrow 2(x+8)=1.5(x+30)$

$\Rightarrow 2x+16=1.5x+45$

$\Rightarrow 0.5x=45-16$

$\Rightarrow x=58$

Hence, the equivalent mass of metal is 58.