Explanation

• Nitrobenzene (C₆H₅NO₂) is reduced to aniline (C₆H₅NH₂).
• Reduction requires removal of oxygen and addition of hydrogen.
• Common lab method uses metals in acidic medium.
• Iron (Fe) with hydrochloric acid (HCl) is widely used (Béchamp reduction).
• It efficiently converts nitro group (–NO₂) to amino group (–NH₂).

Last verified on 20-05-2026

Explanation

• Spontaneity of any reaction depends on Gibbs free energy (ΔG).
• Endothermic reaction absorbs heat, but can still be spontaneous.
• The key condition for spontaneity is that free energy must decrease.
• This happens when system moves to a more stable state.
• So ΔG must be negative.

Last verified on 20-05-2026

Explanation

• Quantum numbers must follow fixed rules.
• For a given principal quantum number n, azimuthal quantum number l = 0 to (n−1).
• If n = 3, possible l values are 0, 1, 2 only.
• So l = 3 is not allowed for n = 3.
• Therefore that set is invalid.

Last verified on 20-05-2026

Explanation

For l=2, it represents the d-subshell.

A d-subshell has 5 orbitals, and each orbital can hold 2 electrons.

So total electrons = 5 × 2 = 10.

Last verified on 20-05-2026

Explanation

• Effusion is the escape of gas molecules through a tiny hole.
• According to Graham’s law, rate of effusion ∝ 1/√molar mass.
• Lighter gases effuse faster than heavier gases.
• Among given options, hydrogen has the lowest molar mass (H₂ = 2 g/mol).
• Therefore, it moves and escapes the fastest.

Last verified on 19-05-2026

Explanation

• Vapour pressure depends on the tendency of liquid molecules to escape into vapour.
• When temperature increases, molecules gain kinetic energy.
• More molecules escape from liquid phase into vapour phase.
• This increases the vapour pressure at equilibrium.
• Pressure applied from outside does not increase vapour pressure directly.

Last verified on 20-05-2026

Explanation

• Boiling point depends on intermolecular forces.
• Stronger forces require more energy to separate molecules.
• Water (H₂O) forms strong hydrogen bonding between molecules.
• H₂S has only weak van der Waals (no effective hydrogen bonding).
• Therefore, water has a much higher boiling point.

Last verified on 20-05-2026

Explanation

• A supercritical fluid forms above critical temperature and pressure.
• In this state, substance shows properties of both liquid and gas.
• It can diffuse like a gas and dissolve substances like a liquid.
• The liquid and gas phases become indistinguishable.
• Therefore, no clear boundary exists between them.

Last verified on 19-05-2026

Explanation

• A 3-center 2-electron (3c–2e) bond involves three atoms sharing two electrons.
• This type of bonding occurs in electron-deficient compounds.
• Diborane (B₂H₆) is a famous example of such bonding.
• It contains two bridging hydrogen atoms between boron atoms.
• These bridges form banana-shaped 3c–2e bonds.

Last verified on 19-05-2026

Explanation

• Ionization energy is energy required to remove an electron from an atom.
• Nitrogen has configuration: 1s² 2s² 2p³ (half-filled, stable).
• Oxygen has configuration: 1s² 2s² 2p⁴.
• In oxygen, one p orbital has paired electrons, causing repulsion.
• This repulsion makes electron removal easier in oxygen than nitrogen.

Last verified on 19-05-2026