Question

Blue vitriol has:
(A) Ionic bond
(B) Coordinate bond
(C) Hydrogen bond
(D) All of the above

Answer 1

Blue vitriol is the common name for copper sulphate pentahydrate because of its characteristic blue colour. The formula for blue vitriol or copper sulphate pentahydrate is written as ${\text{CuS}}{{\text{O}}_{\text{4}}}.5{{\text{H}}_2}{\text{O}}$ . It is formed by two different compounds, i.e. copper sulphate and water. To answer this question, you must recall the bonding and structures of the atoms in sulphate ion, then the bonding between copper and sulphate ion and finally the bond formed by the water molecule and copper sulphate molecules.

Complete step by step solution:
First we consider sulphate ions. Sulphate ion is made up of one sulphur atom bonded to four oxygen atoms. The sulphur atom is the central atom and is surrounded by four oxygen atoms. Sulphur has 6 valence electrons and thus forms $\pi$ bonds only with two oxygen atoms. All the bonds are covalent. The two singly bonded oxygen atoms have unsatisfied valency and thus they accept the electrons released by copper forming an ionic bond resulting into the formation of copper sulphate.
We know that copper has vacant $d -$ orbitals and the oxygen atom in water carries a lone pair of electrons. So the lone pairs of water are coordinated into the empty orbitals forming a coordinate covalent bond.
Thus, blue vitriol has all ionic, covalent and coordinate bonds.
Thus, the correct answer is D.

Note:
Care should be taken so as to avoid getting confused between covalent bonds and coordinate covalent bonds. Although both the bonds are those formed by non- metals and both involve equal sharing of the electron pair by both the atoms, but the electrons in the shared pair come from both the atoms in a covalent bond and in a coordinate covalent bond, the entire shared pair of electrons is donated by a single electron rich species.