Question

The compound which does not exist as hydrate form:
A) Ferrous sulphate
B) Copper sulphate
C) Magnesium sulphate
D) Sodium chloride

Answer 1

Hint: Sulphate is a salt that forms when sulfuric acid reacts with other chemicals giving hydrates as one of the products. Sulphate ion is a polyatomic ion with the empirical formula of $S{O_4}^{2 - }$.

Complete answer:
The sulfate anion consists of a central sulfur atom surrounded by four equivalent oxygen atoms in a tetrahedral arrangement. The sulfur atom is in the + 6 oxidation state while the four oxygen atoms are each in the - 2 state. The sulfate ion carries an overall charge of - 2 and it is the conjugate base of the bisulfate (or hydrogen sulfate) ion, $HS{O_4}^ - $. It forms two pi bonds with d orbitals. It reacts with metal to form an ionic complex which is highly soluble in nature. When sulphuric acid reacts with any metal hydrate is released. Such reactions are exothermic reactions giving different types of hydrates as tetrahydrate, hexahydrate or octahydrate.
In the above question to form a hydrate in presence of sulphuric acid
Ferrous sulphate is a complex with chemical formula $FeS{O_4}.7{H_2}O$. Copper sulphate is the one with formula $CuS{O_4}.5{H_2}O$ magnesium sulphate with $MgS{O_4}.7{H_2}O$ whereas Sodium chloride is the salt formed when sodium reacts with chloride ion giving rise to NaCl. There is no hydrate formation in sodium chloride.

Therefore the correct option is option (D).

Note: A reaction with sulphuric acid produces hydrate to balance off the oxidation state of sulphur and oxygen. Sodium chloride and water is formed when sodium hydroxide and Hydrogen chloride reacts with each other.