📚🌟 Model Test – Acids, Bases & Salts
⚗️🧮 XI Chemistry
✍️🧮 Short Answer Questions 🎯📘
✍️🧮 Descriptive Questions 🎯📘
🔢 📖 Numerical Problems 🧮✨
📘✨ Textbook MCQs on Acids, Bases and Salts
Q1. H₂SO₄ is stronger acid than CH₃COOH because:
✅ Answer: (c)
Explanation: Acid strength depends on degree of ionization and Ka. H₂SO₄ has ~60% ionization and Ka ≈ 10³, making it very strong. CH₃COOH has only ~1.4% ionization and Ka ≈ 1.7×10⁻⁵, so it is weaker.
Q2. Which statement is not correct about bases?
✅ Answer: (d)
Explanation: Bases turn red litmus paper blue, not blue litmus red.
Q3. Al₂O₃ is amphoteric oxide because it reacts with:
✅ Answer: (c)
Explanation: Amphoteric oxides react with both acids and bases to form salt and water. Examples: Al₂O₃, ZnO, BeO, SnO₂, PbO₂, Cr₂O₃.
Q4. Which of the following is NOT a buffer solution?
✅ Answer: (d)
Explanation: Buffer = weak acid + salt of strong base OR weak base + salt of strong acid. NaOH/HCl are both strong, so not a buffer.
Q5. Which oxide is amphoteric in nature?
✅ Answer: (d)
Explanation: Al₂O₃ reacts with both acids and bases. Basic oxides: K₂O, Na₂O, CaO. Acidic oxides: CO₂, SO₂, P₂O₅. Neutral oxides: CO, NO.
Q6. Which of the following does not alter the pH of a solution?
✅ Answer: (c)
Explanation: Neutral salts formed from strong acids and strong bases like NaCl, KBr, KNO₃ etc. do not change the pH of solution.
Q7. Conjugate acid of NH₃ is:
✅ Answer: (a)
Explanation: Adding H⁺ to NH₃ gives NH₄⁺ (conjugate acid). Removing H gives NH₂⁻ (conjugate base).
Q8. Salt formed by neutralization of weak acid and strong base is:
✅ Answer: (c)
Explanation: Na₂CO₃ is formed from weak acid H₂CO₃ and strong base NaOH.
Q9. A conjugate acid-base pair differs by only:
✅ Answer: (b)
Explanation: Conjugate acid-base pairs differ by a single proton (H⁺). Example: NH₃/NH₄⁺, HCl/Cl⁻.
Q10. Salt formed by neutralization of weak acid and weak base is:
✅ Answer: (c)
Explanation: NH₄CN is formed from weak acid HCN and weak base NH₄OH.
📘✨ Newly Compiled Textbook MCQs on Acids, Bases and Salts
Q1. The aqueous solution of KCl is:
✅ Answer: (a)
Explanation: KCl is a neutral salt formed from strong acid (HCl) and strong base (KOH).
Q2. Which one of the following yields a basic solution?
✅ Answer: (c)
Explanation: Sodium acetate is a salt of weak acid (CH₃COOH) and strong base (NaOH), giving basic solution.
Q3. Universal indicator turns red in:
✅ Answer: (c)
Explanation: Universal indicator shows red in strongly acidic solutions (pH < 4).
Q4. Which one of the following is NOT a strong acid?
✅ Answer: (a)
Explanation: HF is a weak acid compared to strong acids like HCl, HNO₃, and H₂SO₄.
Q5. Which one of the following substances has pH value more than 7?
✅ Answer: (b)
Explanation: Sodium carbonate is a basic salt, so its aqueous solution has pH > 7.
Q6. Which one of the following is NOT a salt of weak acids and strong bases?
✅ Answer: (c)
Explanation: Ammonium chloride is a salt of weak base (NH₄OH) and strong acid (HCl).
Q7. Which one of the following is NOT a salt of strong acids and weak bases?
✅ Answer: (c)
Explanation: Sodium acetate is a salt of weak acid (CH₃COOH) and strong base (NaOH).
Q8. Which one of the following salts dissolves in water to produce a solution with pH less than 7?
✅ Answer: (d)
Explanation: None of these salts produce an acidic solution (pH < 7) when dissolved in water.
Q9. Which one of the following salts dissolves in water to produce a solution with pH more than 7?
✅ Answer: (d)
Explanation: None of these salts produce a basic solution (pH > 7) when dissolved in water.
Q10. Which of the following salts has no water of crystallization?
✅ Answer: (c)
Explanation: Baking soda (NaHCO₃) does not contain water of crystallization, unlike gypsum or washing soda.
Q11. Which ion is not present in dilute sulfuric acid?
✅ Answer: (c)
Explanation: Dilute H₂SO₄ contains H⁺ and SO₄²⁻ ions, not SO₃²⁻.
Q12. Which salt is NOT derived from a strong acid and a strong soluble base?
✅ Answer: (a)
Explanation: MgCl₂ comes from strong acid HCl but weakly soluble base Mg(OH)₂.
Q13. The aqueous solution of NaCl is:
✅ Answer: (a)
Explanation: NaCl is a neutral salt formed from strong acid (HCl) and strong base (NaOH).
Q14. Which one of the following yields a basic solution?
✅ Answer: (c)
Explanation: KCN is a salt of weak acid (HCN) and strong base (KOH), giving basic solution.
Q15. Universal indicator turns green in:
✅ Answer: (a)
Explanation: Universal indicator shows green in neutral solutions (pH ≈ 7).
Q16. NH₃ can be a base according to:
✅ Answer: (d)
Explanation: NH₃ acts as a base in Bronsted-Lowry (proton acceptor) and Lewis (electron donor) theories.
Q17. Which of the following is a Lewis base?
✅ Answer: (b)
Explanation: CN⁻ can donate an electron pair, so it is a Lewis base.
Q18. A substance that can donate a pair of electrons to form coordinate covalent bond:
✅ Answer: (d)
Explanation: Lewis bases donate electron pairs to form coordinate covalent bonds.
Q19. If pH value is greater than 7, then solution is:
✅ Answer: (b)
Explanation: Solutions with pH > 7 are basic (alkaline).
Q20. Which of the following is an acid-base conjugate pair?
✅ Answer: (c)
Explanation: H₂CO₃ and CO₃²⁻ differ by one proton, making them a conjugate acid-base pair.
Q21. What will be the pH of aqueous solution of NH₄Cl?
✅ Answer: (d)
Explanation: NH₄Cl is a salt of weak base (NH₄OH) and strong acid (HCl), so its solution is acidic (pH < 7).
Q22. Which one of the following is non-hydrolyzable salt?
✅ Answer: (b)
Explanation: NaCl is a neutral salt of strong acid (HCl) and strong base (NaOH), hence non-hydrolyzable.
Q23. Aqueous solution of NaCl has a pH:
✅ Answer: (a)
Explanation: NaCl solution is neutral with pH = 7.
Q24. Hydrolysis of potassium acetate gives:
✅ Answer: (a)
Explanation: Potassium acetate is a salt of weak acid (CH₃COOH) and strong base (KOH), giving basic solution.
Q25. Aqueous solution of CuSO₄ has a pH:
✅ Answer: (b)
Explanation: CuSO₄ solution is acidic due to hydrolysis of Cu²⁺ ions, so pH < 7.
Q26. Which of the following phenomena will occur when a small amount of acid is added to water?
✅ Answer: (d)
Explanation: Adding acid to water causes dilution and ionization of the acid molecules.
Q27. Strong bases are:
✅ Answer: (b)
Explanation: Strong bases like NaOH and KOH ionize completely in water, acting as strong electrolytes.
Q28. Whose definition of acids and bases emphasizes the role of protons?
✅ Answer: (c)
Explanation: Brønsted-Lowry theory defines acids as proton donors and bases as proton acceptors.
Q29. An electron-pair acceptor is a:
✅ Answer: (c)
Explanation: Lewis acids accept electron pairs, while Lewis bases donate them.
Q30. Which one of the given is hydracid?
✅ Answer: (b)
Explanation: Hydracids are acids composed of hydrogen and a non-metal; HCN is a hydracid.
Q31. Which element is always present in Arrhenius acid?
✅ Answer: (b)
Explanation: Arrhenius acids always contain hydrogen, which they release as H⁺ ions in solution.
Q32. Ammonium sulphate salt is:
✅ Answer: (c)
Explanation: Ammonium sulphate is formed from weak base (NH₄OH) and strong acid (H₂SO₄), so it is acidic.
Q33. Which of the following does not form an acidic salt?
✅ Answer: (b)
Explanation: HCl is a monoprotic strong acid, so it cannot form acidic salts.
Q34. A Brønsted-Lowry base is defined as:
✅ Answer: (c)
Explanation: Brønsted-Lowry bases are defined as proton (H⁺) acceptors.
Q35. The number of water molecules attached to the ionic compounds depends upon………. of the ion.
✅ Answer: (c)
Explanation: The extent of hydration depends on the charge density of the ion; higher charge density attracts more water molecules.
Q36. Which one of the following ions is readily hydrated?
✅ Answer: (a)
Explanation: Al³⁺ has high charge density, so it is strongly hydrated compared to Mg²⁺ or Na⁺.
Q37. Which of the following is readily hydrated?
✅ Answer: (a)
Explanation: Cations attract water molecules more strongly due to their positive charge.
Q38. The number of water molecules attached to the ionic compounds depends upon………. of the ion.
✅ Answer: (c)
Explanation: Hydration depends on both charge and ionic size; higher charge density increases hydration.
Q39. A salt X is dissolved in water of pH 7, the resulting solution becomes alkaline in nature. Salt X is made up of:
✅ Answer: (a)
Explanation: Salts of weak acids and strong bases hydrolyze to give alkaline solutions.
Q40. A salt X is dissolved in water of pH 7, the resulting solution becomes acidic in nature. Salt X is made up of:
✅ Answer: (d)
Explanation: Salts of strong acids and weak bases hydrolyze to give acidic solutions.
Q41. Which of the given is a strong base?
✅ Answer: (d)
Explanation: Potassium hydroxide (KOH) is a strong base because it ionizes completely in aqueous solution.
Q42. An indicator is one kind of the following compound:
✅ Answer: (c)
Explanation: Indicators are weak acids or bases that change color depending on the pH of the solution.
Q1. Define pH and pOH of a solution. Also show that pH + pOH = 14.
💧 pH (Power of Hydrogen → power of H⁺ ion concentration)
Defined as: the negative logarithm of the molar hydrogen ions concentration [H⁺] (in mol/litre) of an aqueous solution at a given temperature.
Formula: pH = −log [H⁺] = log 1/[H⁺] AND [H⁺] = antilog (−pH)
Acidity Indicator: Measures acidity of solution.
Range: 0–14.
✨ Extra Note:
➡️Low pH (0–6) → acidic 🍋
➡️pH = 7 → neutral 💧
➡️High pH (8–14) → basic 🧼
🌊 pOH (Power of Hydroxide → power of OH⁻ ion concentration)
Defined as: the negative logarithm of molar concentration of OH− ion in aqueous solution at a given temperature.
pOH = −log [OH⁻] = log 1/[OH⁻] AND [OH⁻] = antilog (−pOH)
basicity Indicator: Measures basicity of solution.
Range: 0–14.
🎯 Relation Between pH & pOH (pH + pOH = 14 (neutral water at 25°C)
From water dissociation constant:
Kꙍ = [H⁺][OH⁻] = 1×10⁻¹⁴
Taking negative log:
(−log Kꙍ = (−log [H⁺]) (−log [OH⁻])
−log (1 x 10⁻¹⁴) = (−log [H⁺]) (−log [OH⁻])
14 = pH + pOH or pH + pOH = 14 (at 25°C)
Q2. Why the aqueous solution of NH₄Cl is acidic and Na₂CO₃ is alkaline.
🔎 🟥 Hydrolysis of Salts of Strong Acid and Weak Base (Acidic Salts → Cationic Hydrolysis)
🧪 Formed by strong acid + weak base.
⚡ Anion (from strong acid) → no hydrolysis.
💧 Cation (from weak base) → reacts with water → releases H⁺ (Cationic Hydrolysis).
📉 pH < 7 → solution becomes acidic.
✨ Examples: NH₄Cl, (NH₄)₂SO₄, CuCl₂.
🎯 Quick Memory Cue: 👉 Strong acid + weak base → cation hydrolyzes → acidic solution (pH < 7).
🟥 NH₄Cl → Acidic Solution (Cationic Hydrolysis)
➡️Formed from strong acid (HCl) + weak base (NH₄OH).
➡️Cl⁻ (anion from strong acid) → no hydrolysis.
➡️NH₄⁺ (cation from weak base) → strong conjugate acid → hydrolyzes with water → releases H⁺ ions → pH < 7 → acidic
➡️NH₄Cl ⇌ NH₄⁺ + Cl⁻ (Ionization)
➡️NH₄⁺ + H–OH → NH₄OH + H⁺ (Cationic Hydrolysis)
🔎 🟦 Hydrolysis of Salts of Weak Acid and Strong Base (Basic Salts → Anionic Hydrolysis)
🧪 Formed by weak acid + strong base.
⚡ Anion (from weak acid) → reacts with water → releases OH⁻ (Anionic Hydrolysis).
💧 Cation (from strong base) → no hydrolysis.
📉 pH > 7 → solution becomes basic.
✨ Examples: Na₂CO₃, CH₃COONa, NaHCO₃ etc.
🎯 Quick Memory Cue: 👉 weak acid + Strong base → anion hydrolyzes → Basic solution (pH > 7).
🟦 Na₂CO₃ → Alkaline Solution (Anionic Hydrolysis)
➡️Formed from weak acid (H₂CO₃) + strong base (NaOH).
➡️Na⁺ (cation from strong base) → no hydrolysis.
➡️CO₃²⁻ (anion from weak acid) → strong conjugate base → hydrolyzes with water → releases OH⁻ ions → pH > 7 → basic solution
➡️Na₂CO₃ ⇌ 2Na⁺ + CO₃²⁻ (Ionization)
➡️CO₃²⁻ + 2H–OH → H₂CO₃ + 2OH⁻
🎯 Quick Memory Cue
🟥 NH₄Cl → cationic hydrolysis → acidic (pH < 7).
🟦 Na₂CO₃ → anionic hydrolysis → alkaline (pH > 7).
Q3. Write down conjugate base of each of the following acids: H₂SO₄, H₂S, NH₄⁺, HCOOH
🧪 Acid (Species) ➖ Remove H⁺ 🎯 Conjugate Base
H₂SO₄ − H⁺ → HSO₄⁻
H₂S − H⁺ → HS⁻
NH₄⁺ − H⁺ → NH₃
HCOOH − H⁺ → HCOO⁻
🎯 Quick Memory Cue
Conjugate base = acid minus one proton (H⁺).
Conjugate acid = base add one proton (H⁺).
Stronger acid → weaker conjugate base ⚖️.
Weaker acid → stronger conjugate base 💪.
Alternate Smart Style
🔢 Conjugate Bases of Given Acids
➡️H₂SO₄ → remove one proton (H⁺) → HSO₄⁻
➡️H₂S → remove one proton (H⁺) → HS⁻
➡️NH₄⁺ → remove one proton (H⁺) → NH₃
➡️HCOOH → remove one proton (H⁺) → HCOO⁻
🎯 Quick Memory Cue
Conjugate base = acid minus one proton (H⁺).
Conjugate acid = base add one proton (H⁺).
Stronger acid → weaker conjugate base ⚖️.
Weaker acid → stronger conjugate base 💪.
Q4. What is meant by self-ionization of water? Write the expression of Kw. What is its value at 25°C?
💧Water Electrolytic Nature
Water is mostly non electrolyte but conducts slightly due to auto ionization.
One H₂O donates a proton to another → forms H₃O⁺ and OH⁻.
Self Ionization of Water Equation: H₂O + H₂O ⇌ H₃O⁺ + OH⁻
Basis of Expression
💧 Water ionizes slightly → H₃O⁺ + OH⁻
🔄 Equilibrium established characterized by an equilibrium constant (Kc) at a given temperature
📉 Unionized water in large excess ≈ constant
⚡ Kw = ionic product of water → equilibrium constant for water auto-ionization equilibrium → very small value
⚡ Expression of Kw (Ionic Product of Water/ Ionic-Product constant/ Dissociation or ionization constant)
Kc = [H₃O⁺][OH⁻]/[H₂O][H₂O]
Kc = [H₃O⁺][OH⁻]/[H₂O]² ([H₂O]² = constant)
Kc·[H₂O]² = [H₃O⁺][OH⁻]
Kꙍ = [H₃O⁺][OH⁻] (Kc·[H₂O]² = Kꙍ = constant)
Kw = product of molar concentrations of H₃O⁺ (hydrogen ion) and OH⁻ (hydroxide ion) at a particular temperature (at 25°C).
At 25°C, Kw = 1×10⁻¹⁴ mol²/dm⁶
🎯 Quick Memory Cue
💧 Self ionization → H₂O ⇌ H₃O⁺ + OH⁻
⚡ Kw = [H₃O⁺][OH⁻]
📉 Value at 25°C = 1×10⁻¹⁴
Q5. Write equation and indicated the conjugate acid-base pairs for the following:
(i) Acetic acid and ammonia (ii) Hydrochloric acid and water
CH₃COOH + NH₃(g) ⇌ NH₄⁺(aq) + CH₃COO⁻(aq)
(Acid) (Base) (Conjugate acid) (Conjugate base)
HCl(aq) + H₂O ⇌ H₃O⁺(aq) + Cl⁻(aq)
(Acid) (Base) (Conjugate acid) (Conjugate base)
Q6. Define and explain acidic, basic and amphoteric oxides with example.
Metal Oxides
Metal oxides are basic in nature and they are readily dissolves in water to produced respective soluble metal hydroxide producing alkaline solution.
e.g. Na₂O, K₂O, CaO etc.
Na₂O(s) + H₂O(l) → 2NaOH(aq)
K₂O(s) + H₂O(l) → 2KOH(aq)
CaO(s) + H₂O(l) → Ca(OH)₂(aq)
Non-metal Oxides
Non-metal oxides are acidic in nature and they are readily dissolves in water to produced respective oxyacid producing acidic solution.
e.g. CO₂, SO₂, P₂O₅ etc.
CO₂(g) + H₂O(l) → H₂CO₃(aq)
SO₂(g) + H₂O(l) → H₂SO₃(aq)
P₂O₅(g) + H₂O(l) → 2H₃PO₄(aq)
Amphoteric Oxides
Certain amphoteric metal oxides which are insoluble in water have ability to react with both acid and base and are borderline of both acid and base are called amphoteric oxides or amphoteric substances.
e.g. Al₂O₃, ZnO etc.
Al₂O₃(s) + 2NaOH(aq) → 2NaAlO₂ + H₂O(l)
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