Which of the following reactions is a combination reaction? MCQ with Answer and Explanation

Explanation:
N₂ has a triple bond (N≡N), consisting of one sigma and two pi bonds. This is the strongest type of covalent bond, giving N₂ high stability and low reactivity. Bond order is 3. The molecule is diatomic and nonpolar.

Explanation:
Bakelite is a thermosetting plastic (phenol-formaldehyde resin). Once set, it cannot be remolded by heating because its polymer chains are cross-linked. Polyethylene, PVC, and nylon are thermoplastics—they can be repeatedly softened by heat and hardened on cooling. Thermosetting plastics are used for electrical switches, handles, and adhesives. Vulcanized rubber is also thermoset.

Explanation:
Synthetic detergents (like alkyl sulfates or sulfonates) form soluble calcium and magnesium salts, so they lather well even in hard water. Soaps form scum. Detergents are usually derived from petrochemicals, can be non-biodegradable if branched, and may cause pollution.