Problem 89 - A Complete Resource Book in Chemistry for JEE Main

Question

Among the following compounds which contain all 3 type of bonds (i) \(\mathrm{NH}_{4} \mathrm{Cl}\) (ii) \(\mathrm{K}_{3} \mathrm{Fe}(\mathrm{CN})_{6}\) (iii) \(\mathrm{H}_{2} \mathrm{O}_{2}\) (iv) \(\mathrm{H}_{2} \mathrm{SO}_{4}\) (v) \(\mathrm{CaCO}_{3}\) (a) I, II (b) I, II, V (c) I, II, IV (d) I, II, III

Step-by-Step Solution

Answer

The correct answer is (a) I, II.

Step 1: Identify the types of bonds

We need to determine which of these compounds contain all 3 types of bonds: ionic bonds, covalent bonds, and coordinate (also known as dative covalent) bonds.

Step 2: Analyze NH4Cl

For \( \mathrm{NH}_{4} \mathrm{Cl} \): The molecule contains ionic bonds between \( \mathrm{NH}_{4}^{+} \) and \( \mathrm{Cl}^{-} \). Covalent bonds are present within the ammonium ion. Thus, the molecule shows both ionic and covalent bonding. Coordinate bonds also exist because the nitrogen atom donates a pair of electrons to form the bond with the hydrogen atom (in \( \mathrm{NH}_{4}^{+} \)).

Step 3: Analyze K3Fe(CN)6

For \( \mathrm{K}_{3} \mathrm{Fe}(\mathrm{CN})_{6} \): This compound has ionic bonds between \( \mathrm{K}^{+} \) ions and the \( [\mathrm{Fe}(\mathrm{CN})_{6}]^{3-} \) complex ion. It has covalent bonds between carbon and nitrogen within the \( \mathrm{CN}^{-} \) groups. Coordinate bonds exist in the interaction between \( \mathrm{Fe}^{3+} \) and \( \mathrm{CN}^{-} \) ions as the electron pairs are donated by cyanide ions.

Step 4: Analyze H2O2

For \( \mathrm{H}_{2} \mathrm{O}_{2} \): The compound only has covalent bonds between hydrogen and oxygen and between two oxygen atoms. There are no ionic or coordinate bonds in \( \mathrm{H}_{2} \mathrm{O}_{2} \), so it does not qualify.

Step 5: Determine if H2SO4 has all bond types

For \( \mathrm{H}_{2} \mathrm{SO}_{4} \): The compound contains covalent bonds between sulfur and oxygen. It can form ions in solution, but as pure \( \mathrm{H}_{2} \mathrm{SO}_{4} \), it does not inherently contain ionic or coordinate bonds in its structure.

Step 6: Analyze CaCO3

For \( \mathrm{CaCO}_{3} \): This compound has ionic bonds between \( \mathrm{Ca}^{2+} \) and \( \mathrm{CO}_{3}^{2-} \) ions. Within the \( \mathrm{CO}_{3}^{2-} \) ion, there are covalent bonds between carbon and oxygen. It does not have coordinate bonds.

Step 7: Conclusion

Based on the analysis, \( \mathrm{NH}_{4} \mathrm{Cl} \) and \( \mathrm{K}_{3} \mathrm{Fe}(\mathrm{CN})_{6} \) are the compounds that contain all three types of bonds: ionic, covalent, and coordinate.

Key Concepts

Ionic Bonds

In an ionic bond, atoms transfer electrons to achieve a full outer electron shell, leading to the formation of charged ions.
These ions with opposite charges attract each other, creating a strong bond.Ionic bonds typically occur between metals and non-metals. Metals, like sodium or potassium, lose electrons to form positively charged ions, while non-metals, like chlorine, gain electrons to form negatively charged ions. This attraction results in compounds like sodium chloride (NaCl).Key features of ionic bonds include:

• High melting and boiling points due to strong attractions.
• Electrical conductivity when dissolved in water or melted.

In \( ext{NH}_4 ext{Cl}\), the ionic bond is between \( ext{NH}_4^+\) and \( ext{Cl}^-\), while in \( ext{K}_3 ext{Fe}( ext{CN})_6\), it is between \( ext{K}^+\) and the \([ ext{Fe}( ext{CN})_6]^{3-}\) complex.
Similarly, in \( ext{CaCO}_3\), it's between \( ext{Ca}^{2+}\) and \( ext{CO}_3^{2-}\).

Covalent Bonds

Covalent bonds form when atoms share electrons to fulfill their outer electron shells.
This type of bond usually occurs between non-metal atoms with similar electronegativities.The shared electrons allow each atom to achieve the electron configuration of a noble gas, resulting in a stable bond.
Molecules like water (H₂O) and carbon dioxide (CO₂) are formed by covalent bonds.Key characteristics of covalent bonds include:

• Typically lower melting and boiling points than ionic compounds.
• Generally poor conductors of electricity.

In \( ext{NH}_4 ext{Cl}\), covalent bonds are present within the \( ext{NH}_4^+\) ion, holding hydrogen atoms around nitrogen.
In \( ext{K}_3 ext{Fe}( ext{CN})_6\), they appear between carbon and nitrogen in \( ext{CN}^-\), while in \( ext{CaCO}_3\), they occur between carbon and oxygen within \( ext{CO}_3^{2-}\).

Coordinate Bonds

Coordinate bonds, or dative covalent bonds, arise when one atom provides both electrons needed to form a covalent bond.
This bond resembles a regular covalent bond in strength and characteristics.Coordinate bonds are common in complex ions and molecules where one atom has a lone pair of electrons.
These lone pairs are used to form bonds with electron-deficient atoms or ions.Unique points about coordinate bonds include:

• They often involve transition metals and ligands in complex ion formation.
• The resulting bonds contribute to the overall stability and characteristics of the compound.

In \( ext{NH}_4 ext{Cl}\), the nitrogen atom shares a lone pair with a hydrogen ion to form \( ext{NH}_4^+\).
In \( ext{K}_3 ext{Fe}( ext{CN})_6\), each \( ext{CN}^-\) donates electron pairs to \( ext{Fe}^{3+}\), establishing strong coordinate bonds that stabilize the complex.