Explanation

Molar mass of CH₄ = 12 (C) + 4×1 (H) = 16 g/mol, so 16 g = 1 mole of CH₄.

At standard temperature and pressure (STP), 1 mole of any gas occupies 22.4 dm³, so CH₄ also occupies 22.4 dm³.

Explanation

Hemoglobin is a large protein (macromolecule) made up of four polypeptide chains, each with a heme group.

It contains approximately 68,000 atoms, including carbon, hydrogen, oxygen, nitrogen, iron, and sulfur.

Explanation

The Pfund series of hydrogen spectral lines occurs when electrons fall to the n = 5 energy level from higher levels.

These transitions emit radiation in the infrared (IR) region of the electromagnetic spectrum.

Explanation

Aluminum sulphate (also called alum) is a common coagulant used to purify potable water by causing suspended impurities to clump together and settle.

It helps remove particles, bacteria, and organic matter by forming flocs during the coagulation-flocculation process.

Explanation

Proteases are enzymes that break down proteins by hydrolyzing peptide bonds.

Enzymes that catalyze hydrolysis reactions belong to the class of Hydrolases.

Explanation

PVC (Polyvinyl chloride) is formed by addition polymerization of vinyl chloride.

Polystyrene is also formed by addition polymerization of styrene (C₆H₅CH=CH₂).

Explanation

Acetyl chloride (CH₃COCl) cannot be prepared directly from acetic acid due to the poor leaving ability of the –OH group.

It requires a chlorinating agent like PCl₅, PCl₃, or SOCl₂ for conversion.

Therefore, it cannot be prepared directly from acetic acid.

Explanation

The reaction NaOH + HCl → NaCl + H₂O is a neutralization reaction between a strong base and a strong acid.

The enthalpy change in such reactions is called the heat of neutralization.

Explanation

NaCl (sodium chloride) is formed by the electrostatic attraction between Na⁺ and Cl⁻ ions.

Such solids are classified as ionic solids due to the presence of ions arranged in a lattice.

Explanation

A solution that distills without change in composition is called an azeotropic mixture.

It behaves like a single substance during boiling, with constant boiling point and composition.