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

(c) I, II, IV contain all three types of bonds.

Step 1: Understanding Bond Types

There are three primary types of bonds: covalent, ionic, and coordinate covalent (also known as dative bonds). A covalent bond is formed when two atoms share electrons, an ionic bond is formed when electrons are transferred from one atom to another resulting in a positively charged cation and a negatively charged anion, and a coordinate bond involves one atom donating both electrons for the bonding.

Step 2: Analyzing Compound (i): NH4Cl

In \(\text{NH}_4\text{Cl} \), the ammonium ion (NH4+) is bonded to a chlorine ion (Cl-) via an ionic bond. Inside the ammonium ion, the nitrogen forms covalent bonds with four hydrogen atoms. Additionally, one of those bonds is a coordinate covalent bond (the nitrogen donates a lone pair to one hydrogen). Therefore, \(\text{NH}_4\text{Cl} \) contains all three bond types.

Step 3: Analyzing Compound (ii): K3Fe(CN)6

In \(\text{K}_3\text{Fe}(\text{CN})_6 \), potassium (K) forms ionic bonds with the complex ion \(\text{Fe}(\text{CN})_6^{3-}\). Inside the complex ion, cyanide (CN-) forms covalent bonds between carbon and nitrogen atoms and coordinate bonds with the central iron atom since the lone pair from nitrogen is donated to the iron atom. Thus, this compound contains all three bond types.

Step 4: Analyzing Compound (iii): H2O2

In \(\text{H}_2\text{O}_2 \), the bonds present are covalent O-H bonds and O-O bonds. This compound does not have ionic or coordinate bonds, so it does not fulfill the criteria of having all three bond types.

Step 5: Analyzing Compound (iv): H2SO4

In \(\text{H}_2\text{SO}_4 \), sulfur forms covalent bonds with oxygen. The hydrogen atoms are bonded ionically with sulfate (SO4) ions. The sulfate ion also includes coordinate covalent bonds with sulfur donating a lone pair to form double bonds with oxygen atoms. This indicates that all three bond types are present.

Step 6: Analyzing Compound (v): CaCO3

In \(\text{CaCO}_3 \), calcium (Ca) forms ionic bonds with the carbonate (CO3) ion. The carbonate ion itself consists of covalent bonds among carbon and oxygen atoms and has resonance structures indicating double bonding, although no coordinate bonds are typically named. Therefore, it does not have coordinate bonds, just the first two bond types.

Step 7: Concluding the Answer

Based on the analysis, \(\text{NH}_4\text{Cl} \), \(\text{K}_3\text{Fe}(\text{CN})_6 \), and \(\text{H}_2\text{SO}_4 \) contain all three types of bonds: ionic, covalent, and coordinate covalent. Thus, the correct option is (c) I, II, IV.

Key Concepts

Ionic Bonds

Ionic bonds are crucial to understanding how compounds interact at a molecular level. These bonds form when electrons are transferred from one atom to another, creating charged particles known as ions.
The atom losing an electron becomes a positively charged cation, while the atom gaining an electron becomes a negatively charged anion.

• This exchange of electrons leads to a strong electrostatic attraction between differing charges.
• Common in compounds such as sodium chloride (table salt), where sodium donates an electron to chlorine.
• Tend to form crystalline structures with high melting and boiling points.

Ionic bonds typically occur between metals, which prefer to lose electrons, and nonmetals, which seek to gain electrons. In the case of \( \text{NH}_4\text{Cl} \), the ammonium ion \( \text{NH}_4^+ \) is positively charged, and the chloride ion \( \text{Cl}^- \) is negatively charged, illustrating a typical ionic interaction.

Covalent Bonds

Covalent bonds form when two atoms share electrons to achieve a stable electron configuration, typically resembling the closest noble gas. This form of bonding usually occurs between nonmetals.
Atoms strive to fill their valence shells to reach this stability.

• Examples include the oxygen we breathe \( \text{O}_2 \) and water \( \text{H}_2\text{O} \).
• Covalent compounds often have low melting and boiling points compared to ionic compounds.
• Bonds can be single, double, or triple, indicating the number of shared electrons.

In \( \text{NH}_4\text{Cl} \), covalent bonds are present between nitrogen and hydrogen within the ammonium ion. Here, both share the necessary electrons, creating a strong bond that holds the molecule together.

Coordinate Covalent Bonds

Coordinate covalent bonds, also known as dative bonds, are unique in that both bonding electrons come from a single atom. This typically occurs when one atom with a lone pair of electrons interacts with a positive or electron-deficient species.
To form a coordinate covalent bond, one atom must have a lone pair of electrons, acting as a donor, while the other should have an empty orbital, acting as an acceptor.

• The resultant bond is often indistinguishable from a typical covalent bond in terms of properties.
• Seen in compounds like \( \text{NH}_4\text{Cl} \) where nitrogen donates a lone pair to a hydrogen ion, forming the ammonium structure.
• Essential in the structure of complex ions such as \( \text{Fe(CN)}_6^{3-} \), where nitrogen atoms coordinate with iron.

These bonds are integral in biology for the function of enzymes and coordination complexes in chemistry.

Compound Analysis

When conducting a compound analysis, the goal is to understand the types of chemical bonds present. A comprehensive examination reveals not only which bonds exist but also explains the interactions occurring within a compound.
For example, in \( \text{K}_3\text{Fe(CN)}_6 \), potassium forms ionic bonds with \( \text{Fe(CN)}_6^{3-} \). Within this complex ion, cyanide ions form covalent bonds between carbon and nitrogen.

• Also, coordinate covalent bonds form as nitrogen donates electrons to the iron atom.
• This multidimensional bonding enhances the compound's stability and reactivity.
• Different bonding types determine the properties and applications of a compound, including solubility, melting point, and conductivity.

Understanding these elements helps chemists manipulate substances for desired reactions, making compound analysis an essential part of chemistry.