Question

$1000g$ aqueous solution of $CaC{{O}_{3}}$ ​ contains $10g$ of calcium carbonate. A concentration of the solution is:
(A) $10ppm$
(B) $100ppm$
(C) $1000ppm$
(D) $10000ppm$

Answer 1

Hint : $CaC{{O}_{3}}$ is known as Calcium carbonate. Calcium carbonate decomposes to form Calcium oxide and emits Carbon dioxide. Calcium oxide has calcium and oxygen; Carbon dioxide has carbon and oxygen. Find the molecular weight of calcium carbonate, the corresponding weight of calcium, oxygen, and carbon of calcium carbonate.

Complete Step By Step Answer:
The molecular formula of Calcium Carbonate is . Calcium Carbonate contains calcium, carbon, and oxygen. Calcium Carbonate on heating decomposes into Calcium Oxide ( $CaO$ ) and emits Carbon dioxide ( $C{{O}_{2}}$ ).
$CaC{{O}_{3}}\text{ }\xrightarrow{\text{ }\Delta \text{ }}\text{ }CaO+C{{O}_{2}}$
This reaction is a decomposition reaction. The atomic weight of Calcium is $40g,$ the atomic weight of Carbon is 12g and the atomic weight of Oxygen is $16g.$ Therefore, the molecular weight of Calcium Carbonate is $\left( 1\times 40 \right)+\left( 1\times 12 \right)+\left( 3\times 16 \right)=40+12+48=100g$
$100$ grams of Calcium Carbonate contains 40 grams of Calcium, $12$ grams of Carbon and $~48$ grams of oxygen. In the same way, $10$ grams of Calcium Carbonate contain four grams of Calcium, $1.2$ grams of Carbon, and $4.8$ grams of Oxygen.
Here we have given $10g$ of $CaC{{O}_{3}}$ it clears that rest is water,
$Concentration(ppm)=\frac{10}{1000}\times {{10}^{6}}=10000ppm$
Therefore the correct answer is option D.

Note :
Do not confuse gram atoms with no. of moles. 1 gram atom is the no. of atoms present in one gram of the substance whereas one mole of a substance has particles and the particles can be atoms, ions or molecules.