Question

The number of water molecule(s) not coordinated to copper ion directly in  $ CuS{{O}_{4}}\cdot 5{{H}_{2}}O $  is:

A) 4

B) 3

C) 1

D) 2

Answer 1

Hint: The hydrated complex given to us is known as copper sulphate pentahydrate. To find the correct answer here, draw the structure of the complex. Here, three types of bonds are involved between the metal,, non-metals and the ligand namely ionic, covalent and coordinate bond.

Complete step by step answer:

Here, the crystal given to us is of copper sulphate. Let us discuss it briefly in order to answer this question. Copper sulphate crystals are formed by the process of crystallization. We can easily prepare these crystals with dilute sulphuric acid and Copper(II) oxide. The copper sulphate crystals are bright blue in colour. It is formed readily by reacting acid with copper oxide. The blue coloured crystals are generally formed by copper sulphate pentahydrate. It is the common form in which it generally exists but the number of water molecules can range anywhere from 0 to 5. So, there are other variants too like, dihydrate or tetrahydrate. Now let us draw the structure and discuss its bonding in order to answer the given question.

Here, the sulphur and oxygen are bonded through a covalent bond (as both of them are non-metals). Between copper and sulphate ions, the bond is ionic (as sulphur is non-metal and the other is metal). And lastly, the copper sulphate hydrated complex is bonded to the ligands i.e. the water molecule through a coordinate bond. We can see clearly from the above diagram that only one water molecule is not directly coordinated to the copper ion.

Therefore, the correct answer is option (C), 1.

Note: As we know, a covalent bond is a chemical bond which involves sharing of electrons between two atoms which gives rise to a stable balance between the attractive and repulsive forces hence, forms a stable bond which we know as covalent bonding. However, in a coordinate covalent bond the sharing is only by one atom i.e. one of the atoms will donate its electron density and the other will accept it. There will be no mutual sharing. We generally find this type of bonding in complex compounds where there is a metal-ligand interaction. We even call this a dipolar bond because the involved atoms are of opposite polarity.