Important Salts — Set 3

Correct Answer: C. Sodium Chloride

• **Sodium Chloride (NaCl)** = compound formed between sodium metal and chlorine gas in ionic bonding. • **Kitchen salt** — essential mineral for taste enhancement and human physiology, regulating water balance. • 💡 Wrong-option analysis: Calcium Chloride: hygroscopic, used as desiccant; Sodium Carbonate: alkaline washing agent; Potassium Chloride: salt substitute, different properties from NaCl.

Correct Answer: B. Sodium Hydrogen Carbonate

• **Sodium Hydrogen Carbonate (NaHCO₃)** = common baking soda in kitchens worldwide for leavening. • **Mild alkaline** — pH-neutral salt that releases CO₂ when heated, non-toxic and food-safe. • 💡 Wrong-option analysis: Sodium Carbonate: too strong an alkali, leaves bitter taste; Calcium Carbonate: chalk-like powder used in supplements; Sodium Hydroxide: caustic substance, dangerous for food use.

Correct Answer: D. Bleaching Powder

• **Bleaching Powder** = contains available chlorine that kills bacteria, viruses, and pathogenic microorganisms. • **Chlorine disinfection** — kills germs by oxidizing cellular components and disrupting microbial growth. • 💡 Wrong-option analysis: Baking Soda: leavening agent, no disinfectant properties; Plaster of Paris: setting agent for medical casts; Washing Soda: softens water, lacks antimicrobial action.

Correct Answer: B. $Na_2CO_3 \cdot 10H_2O$

• **$Na_2CO_3 \cdot 10H_2O$** = decahydrate form contains 10 molecules of water of crystallization. • **Alkaline salt** — dissociates in water to release carbonate ions that soften hard water. • 💡 Wrong-option analysis: $NaHCO_3$: baking soda, monobasic carbonate; $CaOCl_2$: bleaching powder, no water of crystallization; $CaSO_4 \cdot 2H_2O$: gypsum, used in plaster production.

Correct Answer: C. Calcium

• **Calcium (Ca²⁺)** = gypsum is calcium sulfate dihydrate found as mineral deposits worldwide. • **Building material** — converts to Plaster of Paris when partially dehydrated, then rehydrates to form solid structures. • 💡 Wrong-option analysis: Magnesium: forms Epsom salt (MgSO₄), different properties; Sodium: forms soluble sulfates; Aluminum: forms insoluble hydroxides, not sulfates.

Correct Answer: D. Sodium Sulfate

• **Sodium Sulfate (Na₂SO₄)** = decahydrate form named after chemist Johann Glauber who discovered it. • **Historical significance** — first synthetic inorganic compound, key in textile and paper industries. • 💡 Wrong-option analysis: Magnesium Sulfate: Epsom salt used in baths; Potassium Nitrate: gunpowder ingredient; Sodium Chloride: table salt, common salt.

Correct Answer: D. Potassium Nitrate

• **Potassium Nitrate (KNO₃)** = oxidizing agent that provides oxygen for combustion of charcoal and sulfur. • **Gunpowder formula** — combination of KNO₃ (oxidizer), charcoal (fuel), and sulfur creates explosive mixture. • 💡 Wrong-option analysis: Sodium Chloride: inert salt, no oxidizing property; Calcium Chloride: hygroscopic, absorbs moisture; Sodium Carbonate: alkaline salt, incompatible with explosives.

Correct Answer: A. Sodium Nitrate

• **Sodium Nitrate (NaNO₃)** = abundant in Chile's Atacama Desert as natural mineral deposits. • **Fertilizer use** — primary nitrogen source for agriculture before synthetic processes were developed. • 💡 Wrong-option analysis: Calcium Nitrate: more soluble, different historical sources; Ammonium Nitrate: synthetic compound from Haber process; Potassium Nitrate: traditional saltpeter from different sources.

Correct Answer: C. Silver Nitrate

• **Silver Nitrate (AgNO₃)** = 'lunar' from old alchemy term for silver (moon metal), 'caustic' for its corrosive action. • **Cauterizing agent** — historically used in medicine to burn away diseased tissue and warts. • 💡 Wrong-option analysis: Potassium Permanganate: violet oxidizing agent; Sodium Hydroxide: strong alkali for saponification; Silver Bromide: light-sensitive photographic compound.

Correct Answer: D. Ammonium Carbonate

• **Ammonium Carbonate ((NH₄)₂CO₃)** = sublimes at room temperature, releasing pungent ammonia gas. • **Reflex stimulation** — irritates nasal passages and triggers involuntary breathing response in unconscious patients. • 💡 Wrong-option analysis: Sodium Carbonate: inactive, no volatile components; Potassium Carbonate: also non-volatile; Calcium Carbonate: limestone, lacks ammonia-releasing property.