Question

$500 \, g$ impure sample of $\text{CaCO}_{\text{3}}$ on heating gives $\text{70} \, \text{g}$ of $\text{CaO} \text{.}$ Percentage impurities in sample is

• A. 25%
• B. 50%
• C. 75%
• D. 80%

Answer 1

Answer: (C)

$CaCO_{3} \rightarrow CaO+CO_{2}$

Let the % purity is $\text{x}$
Mol: $\frac{500 \times X}{100 \times 100}$ mol

$\frac{500 \times X}{100 \times 100}\times 56=70$

$X=25$

% Impurities $=100-25=75\%$