Cement is mixed with water, it sets into a hard mass due to: MCQ with Answer and Explanation

Explanation:
In chlor-alkali process (electrolysis of concentrated NaCl solution), Cl⁻ ions are oxidized at the anode: 2Cl⁻ → Cl₂(g) + 2e⁻ (chlorine gas). At the cathode, H₂O is reduced: 2H₂O + 2e⁻ → H₂(g) + 2OH⁻, producing hydrogen gas and leaving NaOH in solution. The process uses a diaphragm or membrane cell to keep products separate. Chlorine is used for water treatment and PVC.

Explanation:
Organic fertilizers (compost, manure, bone meal) add humus, improving soil structure, water retention, and aeration. They support beneficial microorganisms that slowly decompose organic matter, releasing nutrients gradually. Unlike synthetic fertilizers, they do not cause sudden nutrient spikes or soil acidification. Biofertilizers like Rhizobium fix nitrogen. Organic farming emphasizes sustainability and reduced chemical inputs.

Explanation:
Ethane: H₃C-CH₃. There is one C-C single bond and six C-H single bonds, total 7 covalent bonds. Each bond is a sigma bond. The structural formula shows 7 bonds. Methane has 4, propane 10. Counting bonds is simple: each line represents a covalent bond.