Problem 129 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following types of bonds are present in \(\mathrm{CuSO}_{4} \cdot 5 \mathrm{H}_{2} \mathrm{O} ?\) (1) electrovalent (2) covalent (3) coordinate Select the correct answer using the code given below. (a) 1 and 2 only (b) 1 and 3 only (c) 1,2 and 3 (d) 2 and 3 only

Step-by-Step Solution

Answer

Option (c) 1, 2, and 3.

Step 1: Understanding the Compound

The compound given is copper(II) sulfate pentahydrate, \(\mathrm{CuSO}_{4} \cdot 5 \mathrm{H}_{2} \mathrm{O}\). In this compound, copper sulfate \(\mathrm{CuSO}_4\) is combined with five molecules of water and forms a crystalline structure through hydration.

Step 2: Identifying Electrovalent (Ionic) Bonds

Electrovalent, or ionic bonds, occur when there is a transfer of electrons from one atom to another, typically between a metal and a non-metal. In \(\mathrm{CuSO}_4\), copper \((\mathrm{Cu}^{2+})\) forms ionic bonds with the sulfate ion \((\mathrm{SO}_4^{2-})\), as there is a transfer of electrons.

Step 3: Identifying Covalent Bonds

Covalent bonds involve the sharing of electrons between atoms. In \(\mathrm{SO}_4^{2-}\), the sulfur atom forms covalent bonds with the four oxygen atoms, sharing electrons to satisfy the octet rule. Additionally, each water molecule \(\mathrm{H}_{2}\mathrm{O}\) also features covalent bonds between hydrogen and oxygen.

Step 4: Identifying Coordinate Bonds

Coordinate bonds occur when one atom donates both electrons required for the bond. In \( \mathrm{CuSO}_{4} \cdot 5 \mathrm{H}_{2} \mathrm{O} \), the water molecules can form coordinate bonds with the copper ion. The lone pairs from the oxygen atoms in water coordinate with the vacant orbitals of \(\mathrm{Cu}^{2+}\) ions.

Step 5: Selecting the Correct Option

We have identified ionic bonds in \(\mathrm{CuSO}_4\), covalent bonds in both \(\mathrm{SO}_4\) and water molecules, and coordinate bonds due to the interaction between copper ions and water molecules. All three types of bonds are present in \( \mathrm{CuSO}_{4} \cdot 5 \mathrm{H}_{2} \mathrm{O} \). Therefore, the correct option is (c) 1, 2, and 3.

Key Concepts

Ionic Bonds

Ionic bonds, often referred to as electrovalent bonds, form when one atom donates an electron to another. This usually happens between metals and non-metals.
In an ionic bond, the

• metal atom loses electrons, becoming a positively charged ion ( \[ \text{cation} \]
• non-metal atom gains those electrons, becoming a negatively charged ion (\[ \text{anion} \])

These opposite charges attract, creating the ionic bond. For instance, in \(\mathrm{CuSO}_4\), copper (Cu) loses electrons to form \(\mathrm{Cu}^{2+}\), and sulfate \((\mathrm{SO}_4^{2-})\) accepts these electrons, resulting in a stable ionic bond. This fundamental bond is what helps hold many compounds together.

Covalent Bonds

Covalent bonds are all about sharing electrons between atoms. Unlike ionic bonds, no electrons are transferred. Instead, the atoms come together to share electrons, achieving stable configurations. This could involve:

• two non-metals sharing electrons equally
• forms molecules like water \((\mathrm{H}_2\mathrm{O})\)
• creating complex structures like sulfate \((\mathrm{SO}_4^{2-})\)

For example, in a sulfate ion, sulfur shares electrons with four oxygen atoms, while in water, hydrogen and oxygen share electrons to form the \(\mathrm{H}_2\mathrm{O}\) molecule. This sharing of electrons is what constitutes covalent bonds. These bonds are fundamental in the formation of molecules crucial for life and industry.

Coordinate Bonds

Coordinate bonds occur when one atom provides both electrons needed to form a bond. This sometimes happens when a molecule or ion can donate a lone pair of electrons.
It's a special type of covalent bond and involves:

• one atom acting as the donor
• another as the acceptor—often a metal

In the compound \(\mathrm{CuSO}_4 \cdot 5\mathrm{H}_2\mathrm{O}\), each water molecule can use one of its oxygen's lone pairs to form a coordinate bond with the copper ion. The copper ion \(\mathrm{Cu}^{2+}\) has vacant orbitals, making it capable of accepting the lone pairs. This results in a strong and unique bond, illustrating how coordinate bonds can add stability and structural complexity, especially in coordination compounds.