Problem 164 - A Complete Resource Book in Chemistry for JEE Main

Question

Match the following \begin{tabular}{ll} \hline Column-I & Column-II \\ \hline (a) \(\mathrm{KHF}_{2}\) & (p) Compound can exist \\ (b) \(\mathrm{KHCl}_{2}\) & (q) Compound is electrolyte in nature \\ (c) \(\mathrm{NF}_{3}\) & (r) Compound shows hydrogen \\ (d) \(\mathrm{PH}_{5}\) & (s) Compound is non electrolyte \\ & (t) Compound can not exist. \\ \hline \end{tabular}

Step-by-Step Solution

Answer

(a)-(p,q); (b)-(t); (c)-(s); (d)-(t).

Step 1: Analyze Compound KHF2

The compound KHF2 is potassium hydrogen fluoride. It is known for forming hydrogen bonds due to the presence of hydrogen. It is a stable compound that can indeed exist and is also an electrolyte as it can disassociate in water. - Thus, KHF2 matches both (p) Compound can exist and (q) Compound is an electrolyte in nature.

Step 2: Analyze Compound KHCl2

The compound KHCl2 suggests the potential existence of di-chloro hydrogen attached to a metal like Potassium. However, this compound is not stable and doesn't exist as a stable entity in real chemical conditions. - Thus, KHCl2 matches (t) Compound can not exist.

Step 3: Analyze Compound NF3

NF3 is nitrogen trifluoride, a molecular compound, and it is non-ionic in nature. Therefore, NF3 does not behave as an electrolyte, meaning it does not disassociate into ions in solution. - Thus, NF3 matches (s) Compound is non-electrolyte.

Step 4: Analyze Compound PH5

PH5 describes a phosphorus atom with five hydrogens, which is not a common or stable compound because phosphorus typically forms three or five bonds with elements like oxygen or halogens, not hydrogen. - Thus, PH5 matches (t) Compound can not exist.

Key Concepts

Potassium Hydrogen Fluoride

Potassium hydrogen fluoride, with the chemical formula \(\mathrm{KHF}_{2}\), is a fascinating compound. It primarily consists of potassium (K), hydrogen (H), and fluoride (F) atoms. One unique feature is its ability to form hydrogen bonds. These hydrogen bonds arise because of the presence of hydrogen atoms which can interact strongly with other electronegative elements like fluorine. This makes \(\mathrm{KHF}_{2}\) stable under normal conditions.
Not only can potassium hydrogen fluoride exist, but it also functions as an electrolyte. An electrolyte is a substance that, when dissolved in water, disassociates into ions, allowing the solution to conduct electricity. So, when \(\mathrm{KHF}_{2}\) dissolves in water, it breaks down into potassium ions \((\mathrm{K}^+)\) and hydrogen fluoride ions \((\mathrm{HF}_{2}^-)\), which can carry an electric current.

Nitrogen Trifluoride

Nitrogen trifluoride, or \(\mathrm{NF}_{3}\), is a compound composed of one nitrogen atom and three fluorine atoms. It is a stable gas at room temperature and is primarily used in the electronics industry for etching silicon wafers and cleaning processes.
\(\mathrm{NF}_{3}\) is known as a non-electrolyte. This is because when it dissolves in a solvent, it does not split into ions. Instead, \(\mathrm{NF}_{3}\) remains intact molecularly. This characteristic means it won’t conduct electricity in its dissolved state.
Non-electrolytes are generally covalent compounds with no free ions available, making \(\mathrm{NF}_{3}\) a typical example of such compounds.

Phosphorus Hydride

Phosphorus hydride, referenced here as \(\mathrm{PH}_{5}\), is an interesting theoretical compound. It suggests a molecule where phosphorus bonds to five hydrogen atoms. However, in reality, \(\mathrm{PH}_{5}\) is not a stable compound under normal chemical conditions. Phosphorus typically prefers to bond with a limited number of hydrogens, as seen in \(\mathrm{PH}_{3}\), known as phosphine, which is a stable molecule.
The instability of \(\mathrm{PH}_{5}\) results from phosphorus's chemistry. Phosphorus forms stable compounds usually in oxidation states of +3 and +5, typically with oxygen or halogens, where its bonding capabilities are maximized. Attempting to form a compound like \(\mathrm{PH}_{5}\) fails in practice due to electron pair repulsion and lack of conducive molecular orbitals needed for stability.

Electrolytes

Electrolytes are crucial to many chemical processes and occur widely in both laboratory and natural settings. These are substances that, when dissolved in water, separate into ions. This separation allows the resulting solution to conduct electricity.
Examples of electrolytes include salts, acids, and bases. Substances like \(\mathrm{KHF}_{2}\) serve as electrolytes because they break down into ions when in aqueous solution. The movement of these ions under an electric field is what enables the solution to act as a conductor.
Understanding electrolytes is key in fields ranging from industrial chemistry to biology, where electrolytes help maintain voltage across cell membranes and relay nerve impulses. Without them, the flow of electricity in aqueous solutions would be impossible.