Important Salts — Set 4
Chemistry · महत्वपूर्ण लवण · Questions 31–40 of 40
Which salt is the main component of 'Rock Salt'?
Correct Answer: D. Sodium Chloride
• **Sodium Chloride (NaCl)** = mineral halite form extracted from underground rock formations and salt mines. • **Geological deposits** — formed from ancient evaporation of seawater, often containing brown iron oxide impurities. • 💡 Wrong-option analysis: Potassium Iodide: trace element in salt, requires fortification; Magnesium Chloride: minor salt component; Calcium Sulfate: gypsum, different mineral formation.
What is the number of water molecules of crystallization in one formula unit of Copper Sulfate?
Correct Answer: D. 5
• **5 molecules of H₂O** = pentahydrate form is CuSO₄·5H₂O, the stable crystalline structure. • **Blue color origin** — hydrated Cu²⁺ ions in crystal lattice cause the characteristic bright blue appearance. • 💡 Wrong-option analysis: 7 molecules: Magnesium sulfate (Epsom salt) contains 7; 2 molecules: rare form, unstable; 10 molecules: Washing soda, not copper sulfate.
Which salt is used as a raw material for making Sodium Hydroxide in the Chlor-alkali process?
Correct Answer: C. Sodium Chloride
• **Sodium Chloride (brine solution)** = electrolyzed to produce NaOH, Cl₂ gas, and H₂ gas via chlor-alkali process. • **Industrial importance** — produces both caustic soda and chlorine gas simultaneously for chemical industry. • 💡 Wrong-option analysis: Sodium Sulfate: source of sulfuric acid, not for chlor-alkali; Sodium Carbonate: produces different products via electrolysis; Sodium Bicarbonate: decomposes, unsuitable for electrolysis.
Which salt is formed when Sodium Hydroxide reacts with Sulfuric acid?
Correct Answer: C. Sodium Sulfate
• **Sodium Sulfate (Na₂SO₄)** = product of strong base-strong acid neutralization: 2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O. • **Neutral salt formation** — both reactants fully dissociate, forming a neutral aqueous solution. • 💡 Wrong-option analysis: Sodium Nitrate: forms with nitric acid, not sulfuric acid; Sodium Carbonate: forms with carbonic acid; Sodium Chloride: forms with hydrochloric acid.
Which of the following is a 'Basic Salt'?
Correct Answer: A. Sodium Acetate
• **Sodium Acetate (CH₃COONa)** = formed from strong base (NaOH) and weak acid (acetic acid). • **Hydrolysis reaction** — acetate ions hydrolyze in water to produce OH⁻ ions, making solution basic (pH > 7). • 💡 Wrong-option analysis: Potassium Nitrate: strong acid-strong base, neutral salt; Ammonium Chloride: weak base-strong acid, acidic salt; Sodium Chloride: strong base-strong acid, neutral salt.
What is the chemical name of the salt used to make 'Saltpeter'?
Correct Answer: D. Potassium Nitrate
• **Potassium Nitrate (KNO₃)** = the primary oxidizing agent in traditional gunpowder formulations. • **Historical importance** — extracted from 'niter caves' and used in military explosives for centuries. • 💡 Wrong-option analysis: Sodium Nitrate: Chile saltpeter, different mineral source; Ammonium Nitrate: synthetic compound used in fertilizers; Calcium Nitrate: alternative nitrate source.
Which salt is used in the 'Fehling's solution' to test for reducing sugars?
Correct Answer: C. Copper Sulfate
• **Copper Sulfate (CuSO₄)** = provides Cu²⁺ ions that oxidize aldehyde groups in reducing sugars. • **Color change** — blue solution turns brick-red precipitate (Cu₂O) when heated with reducing sugars. • 💡 Wrong-option analysis: Ferrous Sulfate: used in different analytical tests; Magnesium Sulfate: non-reactive with sugars; Sodium Chloride: inert in organic reactions.
Which salt is used as a 'Fire Retardant' in many building materials?
Correct Answer: A. Ammonium Phosphate
• **Ammonium Phosphate ((NH₄)₃PO₄)** = thermal decomposition produces phosphoric acid that forms protective char. • **Fire protection mechanism** — char layer insulates underlying material and lowers flammability temperature. • 💡 Wrong-option analysis: Potassium Chloride: hygroscopic but non-reactive in fires; Calcium Chloride: absorbs moisture, promotes burning; Sodium Carbonate: inert, no fire-suppressing property.
Which salt is commonly known as 'Baking Powder' when mixed with a mild edible acid?
Correct Answer: D. Sodium Bicarbonate
• **Sodium Bicarbonate + acid** = tartaric acid or cream of tartar added to create baking powder mixture. • **Dual-action leavening** — acid reacts with base to produce CO₂ before baking, creating better rise. • 💡 Wrong-option analysis: Sodium Carbonate: too alkaline, leaves bitter aftertaste; Potassium Hydroxide: caustic, dangerous for food; Calcium Oxychloride: bleaching powder, unsuitable for cooking.
What is the color of the anhydrous form of Copper Sulfate salt?
Correct Answer: B. White
• **White color** = anhydrous CuSO₄ lacks hydrated Cu²⁺ ions responsible for blue appearance. • **Reversible transformation** — white powder turns blue upon adding water due to rehydration process. • 💡 Wrong-option analysis: Blue: characteristic of pentahydrate form with water molecules; Green: color of CuO (copper oxide); Yellow: color of some other copper compounds like CuCl.