Question

100 g impure CaCO3 on heating gives 5.6 lt. CO2 gas at STP. Find the percentage of calcium in the lime stone sample. [At. wt. : Ca = 40 ; C = 12 ; O = 16]

• A. 10
• B. 20
• C. 1
• D. 30

Answer 1

Answer: (B)

20

Answer 2

(2)

CaCO3 $\longrightarrow$ CaO + CO2

$\frac{5.6}{22.4} = \frac{1}{4}mole$

mole of CaO = mole of Ca =$\frac{1}{4}$

mass of Ca $\frac{1}{4}$= × 40 = 10

% of Ca in sample = $\frac{10}{100}$ × 100 = 10%