Question

The chemical formula of Gypsum is:

• A. ${CaCO}_3\cdot 5H_{2}O$
• B. ${CaSO}_4\cdot 2H_{2}O$
• C. ${CaSO}_4\cdot \frac{1}{2}{H}_{2}O$
• D. ${CaCO}_3\cdot \frac{1}{2}{H}_{2}O$

Answer 1

The correct option is B

${\mathrm{CaSO}}_4·2{\mathrm{H}}_2\mathrm{O}$

Explanation of the correct option:

The correct option is B:

1. The chemical formula of Gypsum is ${\mathrm{CaSO}}_4·2{\mathrm{H}}_2\mathrm{O}$ and it is also known as Calcium Sulphate Dihydrate.
2. It is primarily used in fertilizers, to make plasterboards, and also used in still water to remove impurities. The following equation represents its formation.
3. $\underset{\left(CalciumSulphate\right)}{CaS{O}_4}\left(s\right)+\underset{\left(Water\right)}{2H_{2}O\left(l\right)}\to \underset{\left(Gypsum\right)}{CaS{O}_4.2H_{2}O\left(s\right)}$

Explanation of incorrect options:

1. Option A: The chemical name of ${\mathrm{CaCO}}_3·5{\mathrm{H}}_2\mathrm{O}$ is Calcium Carbonate Pentahydrate whereas the chemical name of Gypsum is Calcium Sulphate Dihydrate.
2. Option C:${\mathrm{CaSO}}_4·\frac{1}{2}{\mathrm{H}}_2\mathrm{O}$ is the chemical formula of Plaster of Paris, not Gypsum.
3. Option D: The chemical name of ${\mathrm{CaCO}}_3·\frac{1}{2}{\mathrm{H}}_2\mathrm{O}$ is Calcium Carbonate Hemihydrate so it doesn't represent Gypsum.

Final Answer: The chemical formula of Gypsum is ${\mathrm{CaSO}}_4·2{\mathrm{H}}_2\mathrm{O}$.