Question

A sample of calamine ore $\left(ZnC{O}_3\right)$ contains clay as an impurity which is $37.5$%. Clay impurity loses some amount of its weight as moisture on prolonged heating. If the total loss in weight of ore on heating (due to $C{O}_2$ and $H_{2}O$) is $28$%, then find the percentage loss in the weight of the clay.

[Given: Atomic mass of $Zn=65,C=12,O=16$]

• A. $16$
• B. $18$
• C. $20$
• D. $25$

Answer 1

Answer: (A)

$16$

A sample of calamine ore $\left(ZnC{O}_3\right)$ contains clay as an impurity which is $37.5$%.

Let the total mass of the sample be $100$ g.

$\therefore m_{ZnC{O}_3}=62.5$ g and $m_{clay}=37.5$ g

$ZnC{O}_3\to ZnO+C{O}_2$

$125$ g of $ZnC{O}_3$ corresponds to $44$ g of $C{O}_2$.

$\therefore 62.5$ g corresponds to $22$ g of $C{O}_2$.

$m_{H_{2}O}+m_{C{O}_2}=28$ g

$\therefore m_{H_{2}O}=28-22=6$ g

$\therefore$ % loss in the weight of clay $=\frac{6}{37.5}\times 100=16$ %