Question

As both calcium and sulphate carry two positive charges the formula of calcium sulphate is ${\text{C}}{{\text{a}}_{\text{2}}}{\left( {{\text{S}}{{\text{O}}_{\text{4}}}} \right)_{\text{2}}}$
Reason: Calcium Sulphate is a compound formed by combination of calcium and sulphate ions
(A) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(B) Both Assertion and Reason are correct But Reason is not the correct explanation of Assertion.
(C) Assertion is correct but Reason is incorrect.
(D) Assertion is incorrect but Reason is correct.

Answer 1

Hint: Calcium sulphate is a salt of calcium. It is a white solid which is barely soluble in water. Its hydrates Gypsum and Plaster of Paris are important compounds as they are used in our daily life.

Step-by-Step Solution:
Calcium sulphate is a natural occurring salt with the chemical formula ${\text{CaS}}{{\text{O}}_{\text{4}}}$. It is formed by the combination of calcium ions and sulphate ions. It can be prepared in the laboratory by treating calcium hydroxide with sulphuric acid due to which neutralization occurs and calcium sulphate is formed.
Calcium ion carries two positive charges ${\text{C}}{{\text{a}}^{{\text{2 + }}}}$ as it donates its two electrons easily to form bond.
Sulphate ion carries two negative charges ${\text{SO}}_4^{2 - }$ as it easily accepts two electrons to complete its octet.
Hence when both ions combine a neutral compound calcium sulphate is formed.
Hence the assertion is incorrect but the reason is correct.

Answer-The correct answer is C.

Additional Information: Plaster of Paris is a semi-hydrate of calcium sulphate with formula ${\text{CaS}}{{\text{O}}_{\text{4}}}{\text{.}}\frac{{\text{1}}}{{\text{2}}}{{\text{H}}_{\text{2}}}{\text{O}}$ which is obtained by heating gypsum ${\text{CaS}}{{\text{O}}_{\text{4}}}.2{{\text{H}}_2}{\text{O}}$ at $393K$.
It is used in building industries and construction of false ceilings.
It is used in making statues and burial sites.
In the medical field it is used as dentures.

Note: The uses of calcium sulphate are-
- It is used in the manufacture of Plaster of Paris and Gypsum.
- It is used in tofu as a coagulant.
- It is used as a moisture indicator.