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Are you a Class 10 ICSE student preparing for your Chemistry board exams? Hydrogen Chloride and Hydrochloric Acid is one of the most important chapters in the ICSE Class 10 Chemistry syllabus. At Dhingra Classes, Nashik, we have designed this comprehensive guide to help you master every concept with 50 solved MCQs, 15 solved short answer questions, and 15 solved long answer questions.

This article covers preparation of hydrogen chloride gas, physical and chemical properties, hydrochloric acid, tests for HCl gas, uses, and numerical problems — all explained step-by-step for easy understanding.

📚 Introduction to Hydrogen Chloride

Hydrogen Chloride (HCl) is a colourless, pungent-smelling gas that is highly soluble in water. When dissolved in water, it forms Hydrochloric Acid, a strong monobasic acid.

🔑 Key Facts:

• Molecular Formula: HCl

• Molecular Mass: 36.5 g/mol

• Nature: Acidic gas

• Solubility: Highly soluble in water (forms hydrochloric acid)

• Nature of Solution: Conducts electricity (strong electrolyte)

🧪 Preparation of Hydrogen Chloride Gas

Laboratory Preparation:

Method: Heating sodium chloride with concentrated sulphuric acid.

Equation:
NaCl + H₂SO₄ → NaHSO₄ + HCl↑

(At higher temperature: 2NaCl + H₂SO₄ → Na₂SO₄ + 2HCl↑)

Apparatus:

• Round-bottom flask

• Thistle funnel

• Delivery tube

• Gas jar

Collection: By upward displacement of air (since HCl is heavier than air and highly soluble in water).

Drying Agent: Concentrated sulphuric acid (H₂SO₄) — not quicklime or caustic soda as they react with HCl.

Industrial Preparation:

Method: Direct combination of hydrogen and chlorine in presence of sunlight.

Equation:
H₂ + Cl₂ → 2HCl (in presence of sunlight)

🧪 Physical Properties of Hydrogen Chloride

🧪 Chemical Properties of Hydrogen Chloride

1. Acidic Nature:

HCl gas is acidic in nature. It turns blue litmus red.

2. Reaction with Ammonia:

NH₃ + HCl → NH₄Cl (White fumes of ammonium chloride)

3. Reaction with Metals:

Zn + 2HCl → ZnCl₂ + H₂↑

4. Reaction with Metal Carbonates:

Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂↑

5. Reaction with Metal Oxides:

CuO + 2HCl → CuCl₂ + H₂O

6. Reaction with Metal Hydroxides:

NaOH + HCl → NaCl + H₂O

🧪 Hydrochloric Acid (Aqueous HCl)

When HCl gas is dissolved in water, it forms Hydrochloric Acid.

Properties:

• Strong monobasic acid

• Colourless liquid

• Corrosive

• Conducts electricity

• pH < 7

Uses of Hydrochloric Acid:

1. In the preparation of chlorine gas

2. In the manufacture of PVC

3. In the pickling of steel

4. In the production of dyes and drugs

5. In the laboratory as a reagent

6. In the digestion of food (stomach acid)

🧪 Tests for Hydrogen Chloride Gas

📝 SECTION 1: 50 SOLVED MCQs on Hydrogen Chloride and Hydrochloric Acid

Q1. The molecular formula of hydrogen chloride is:

(a) H₂O (b) HCl (c) H₂SO₄ (d) HNO₃
Ans: (b) HCl

Q2. Hydrogen chloride gas is:

(a) Basic (b) Acidic (c) Neutral (d) Amphoteric
Ans: (b) Acidic

Q3. The molecular mass of HCl is:

(a) 36.5 (b) 35.5 (c) 37.5 (d) 38.5
Ans: (a) 36.5

Q4. HCl gas is collected by:

(a) Downward displacement of air (b) Upward displacement of air (c) Downward displacement of water (d) Upward displacement of water
Ans: (b) Upward displacement of air

Q5. Which acid is used in the laboratory preparation of HCl?

(a) HNO₃ (b) H₂SO₄ (c) HCl (d) CH₃COOH
Ans: (b) H₂SO₄

Q6. The gas evolved when NaCl reacts with H₂SO₄ is:

(a) Cl₂ (b) HCl (c) SO₂ (d) H₂
Ans: (b) HCl

Q7. HCl gas turns blue litmus:

(a) Blue (b) Red (c) Green (d) Yellow
Ans: (b) Red

Q8. The white fumes produced when HCl reacts with NH₃ is:

(a) NH₄Cl (b) NaCl (c) NH₄OH (d) Cl₂
Ans: (a) NH₄Cl

Q9. Hydrochloric acid is a:

(a) Weak acid (b) Strong acid (c) Neutral compound (d) Base
Ans: (b) Strong acid

Q10. The pH of hydrochloric acid is:

(a) 7 (b) More than 7 (c) Less than 7 (d) 14
Ans: (c) Less than 7

Q11. HCl gas is dried using:

(a) Quicklime (b) Caustic soda (c) Conc. H₂SO₄ (d) P₂O₅
Ans: (c) Conc. H₂SO₄

Q12. The reaction of HCl with Zn produces:

(a) ZnCl₂ + H₂ (b) ZnCl₂ + H₂O (c) ZnCl₂ + CO₂ (d) ZnCl₂ + O₂
Ans: (a) ZnCl₂ + H₂

Q13. HCl reacts with Na₂CO₃ to produce:

(a) CO₂ (b) H₂ (c) O₂ (d) N₂
Ans: (a) CO₂

Q14. The acid present in the stomach is:

(a) H₂SO₄ (b) HCl (c) HNO₃ (d) CH₃COOH
Ans: (b) HCl

Q15. HCl gas is:

(a) Lighter than air (b) Heavier than air (c) Same as air (d) None of these
Ans: (b) Heavier than air

Q16. The nature of HCl gas is:

(a) Acidic (b) Basic (c) Neutral (d) Amphoteric
Ans: (a) Acidic

Q17. HCl gas is highly soluble in:

(a) Oil (b) Water (c) Alcohol (d) Benzene
Ans: (b) Water

Q18. The reaction of HCl with CuO produces:

(a) CuCl₂ + H₂O (b) CuCl₂ + H₂ (c) CuCl₂ + CO₂ (d) CuCl₂ + O₂
Ans: (a) CuCl₂ + H₂O

Q19. The gas produced when HCl reacts with metal carbonates is:

(a) H₂ (b) CO₂ (c) O₂ (d) N₂
Ans: (b) CO₂

Q20. HCl gas is used in the preparation of:

(a) Cl₂ (b) O₂ (c) N₂ (d) H₂
Ans: (a) Cl₂

Q21. The compound formed when HCl reacts with NaOH is:

(a) NaCl + H₂O (b) NaCl + H₂ (c) NaCl + CO₂ (d) NaCl + O₂
Ans: (a) NaCl + H₂O

Q22. HCl gas is liquefied under:

(a) Low pressure (b) High pressure (c) Low temperature (d) Both (b) and (c)
Ans: (d) Both (b) and (c)

Q23. The test for HCl gas using silver nitrate gives:

(a) White precipitate (b) Yellow precipitate (c) Black precipitate (d) No precipitate
Ans: (a) White precipitate

Q24. The white precipitate formed in the test for HCl gas is:

(a) AgCl (b) AgNO₃ (c) Ag₂O (d) Ag₂S
Ans: (a) AgCl

Q25. HCl gas is:

(a) Colourless (b) Green (c) Yellow (d) Brown
Ans: (a) Colourless

Q26. The odour of HCl gas is:

(a) Pleasant (b) Pungent (c) Odourless (d) Sweet
Ans: (b) Pungent

Q27. HCl gas is:

(a) Non-corrosive (b) Corrosive (c) Neutral (d) Basic
Ans: (b) Corrosive

Q28. The reaction of HCl with NH₃ is a:

(a) Combination reaction (b) Decomposition reaction (c) Displacement reaction (d) Double displacement reaction
Ans: (a) Combination reaction

Q29. HCl gas is used in the manufacture of:

(a) PVC (b) Glass (c) Cement (d) Steel
Ans: (a) PVC

Q30. The acid used in the pickling of steel is:

(a) H₂SO₄ (b) HCl (c) HNO₃ (d) CH₃COOH
Ans: (b) HCl

Q31. HCl gas is:

(a) Monobasic (b) Dibasic (c) Tribasic (d) Tetrabasic
Ans: (a) Monobasic

Q32. The reaction of HCl with metals produces:

(a) H₂ (b) O₂ (c) CO₂ (d) N₂
Ans: (a) H₂

Q33. HCl gas is:

(a) Reducing agent (b) Oxidising agent (c) Both (d) None
Ans: (a) Reducing agent

Q34. The gas produced when HCl reacts with Zn is:

(a) H₂ (b) O₂ (c) CO₂ (d) N₂
Ans: (a) H₂

Q35. HCl gas is:

(a) Soluble in water (b) Insoluble in water (c) Sparingly soluble (d) None
Ans: (a) Soluble in water

Q36. The reaction of HCl with CaCO₃ produces:

(a) CaCl₂ + H₂O + CO₂ (b) CaCl₂ + H₂ (c) CaCl₂ + O₂ (d) CaCl₂ + N₂
Ans: (a) CaCl₂ + H₂O + CO₂

Q37. HCl gas is used in the laboratory as:

(a) Oxidising agent (b) Reducing agent (c) Reagent (d) Catalyst
Ans: (c) Reagent

Q38. The reaction of HCl with Mg produces:

(a) MgCl₂ + H₂ (b) MgCl₂ + O₂ (c) MgCl₂ + CO₂ (d) MgCl₂ + N₂
Ans: (a) MgCl₂ + H₂

Q39. HCl gas is:

(a) Polar (b) Non-polar (c) Ionic (d) Metallic
Ans: (a) Polar

Q40. The reaction of HCl with Fe produces:

(a) FeCl₂ + H₂ (b) FeCl₃ + H₂ (c) FeCl₂ + O₂ (d) FeCl₃ + O₂
Ans: (a) FeCl₂ + H₂

Q41. HCl gas is:

(a) Acidic (b) Basic (c) Neutral (d) Amphoteric
Ans: (a) Acidic

Q42. The reaction of HCl with NaHCO₃ produces:

(a) NaCl + H₂O + CO₂ (b) NaCl + H₂ (c) NaCl + O₂ (d) NaCl + N₂
Ans: (a) NaCl + H₂O + CO₂

Q43. HCl gas is:

(a) Toxic (b) Non-toxic (c) Harmless (d) None
Ans: (a) Toxic

Q44. The reaction of HCl with Al produces:

(a) AlCl₃ + H₂ (b) AlCl₃ + O₂ (c) AlCl₃ + CO₂ (d) AlCl₃ + N₂
Ans: (a) AlCl₃ + H₂

Q45. HCl gas is:

(a) Inflammable (b) Non-inflammable (c) Explosive (d) None
Ans: (b) Non-inflammable

Q46. The reaction of HCl with CaO produces:

(a) CaCl₂ + H₂O (b) CaCl₂ + H₂ (c) CaCl₂ + CO₂ (d) CaCl₂ + O₂
Ans: (a) CaCl₂ + H₂O

Q47. HCl gas is:

(a) Heavier than air (b) Lighter than air (c) Same as air (d) None
Ans: (a) Heavier than air

Q48. The reaction of HCl with Pb(NO₃)₂ produces:

(a) PbCl₂ + HNO₃ (b) PbCl₂ + H₂ (c) PbCl₂ + O₂ (d) PbCl₂ + N₂
Ans: (a) PbCl₂ + HNO₃

Q49. HCl gas is:

(a) Colourless (b) Coloured (c) Black (d) White
Ans: (a) Colourless

Q50. The reaction of HCl with AgNO₃ produces:

(a) AgCl + HNO₃ (b) AgCl + H₂ (c) AgCl + O₂ (d) AgCl + N₂
Ans: (a) AgCl + HNO₃

📝 SECTION 2: 15 SOLVED SHORT ANSWER QUESTIONS on Hydrogen Chloride and Hydrochloric Acid

Q1. How is hydrogen chloride gas prepared in the laboratory?

Ans:
Hydrogen chloride gas is prepared by heating sodium chloride with concentrated sulphuric acid.
NaCl + H₂SO₄ → NaHSO₄ + HCl↑
The gas is collected by upward displacement of air.

Q2. Why is HCl gas collected by upward displacement of air?

Ans:
HCl gas is collected by upward displacement of air because it is heavier than air and highly soluble in water.

Q3. What is the nature of HCl gas? How is it tested?

Ans:
HCl gas is acidic in nature. It turns blue litmus red. When a glass rod dipped in ammonium hydroxide is brought near HCl gas, white fumes of ammonium chloride are formed.

Q4. Write the reaction of HCl with ammonia.

Ans:
NH₃ + HCl → NH₄Cl
White fumes of ammonium chloride are formed.

Q5. What happens when HCl gas is dissolved in water?

Ans:
When HCl gas is dissolved in water, it forms hydrochloric acid, a strong monobasic acid. The solution conducts electricity.

Q6. Write the reaction of HCl with zinc.

Ans:
Zn + 2HCl → ZnCl₂ + H₂↑
Hydrogen gas is evolved.

Q7. Write the reaction of HCl with sodium carbonate.

Ans:
Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂↑
Carbon dioxide gas is evolved.

Q8. What is the action of HCl on blue litmus paper?

Ans:
HCl turns blue litmus paper red, indicating its acidic nature.

Q9. Why is HCl gas not dried using quicklime?

Ans:
HCl gas is not dried using quicklime because quicklime (CaO) is a base and reacts with HCl to form calcium chloride and water.

Q10. What is the test for hydrochloric acid using silver nitrate?

Ans:
When silver nitrate solution is added to hydrochloric acid, a white precipitate of silver chloride (AgCl) is formed.
AgNO₃ + HCl → AgCl↓ + HNO₃

Q11. Write the reaction of HCl with copper oxide.

Ans:
CuO + 2HCl → CuCl₂ + H₂O
Copper chloride and water are formed.

Q12. What is the action of HCl on sodium hydroxide?

Ans:
NaOH + HCl → NaCl + H₂O
Neutralisation reaction occurs, forming sodium chloride and water.

Q13. Why is hydrochloric acid used in the stomach?

Ans:
Hydrochloric acid is present in the stomach to digest food and kill bacteria. It provides an acidic medium for the action of enzymes like pepsin.

Q14. What is the industrial method for the preparation of HCl?

Ans:
Industrially, HCl is prepared by the direct combination of hydrogen and chlorine in the presence of sunlight.
H₂ + Cl₂ → 2HCl

Q15. Write two uses of hydrochloric acid.

Ans:

1. In the preparation of chlorine gas.

2. In the manufacture of PVC and dyes.

📝 SECTION 3: 15 SOLVED LONG ANSWER QUESTIONS on Hydrogen Chloride and Hydrochloric Acid

Q1. Describe the laboratory preparation of hydrogen chloride gas with a labelled diagram.

Ans:
Laboratory Preparation:

• Apparatus: Round-bottom flask, thistle funnel, delivery tube, gas jar.

• Chemicals: Sodium chloride (NaCl) and concentrated sulphuric acid (H₂SO₄).

• Method: NaCl is taken in the flask. Conc. H₂SO₄ is added through the thistle funnel. The flask is heated. HCl gas is evolved.

• Equation: NaCl + H₂SO₄ → NaHSO₄ + HCl↑

• Collection: By upward displacement of air.

• Drying: By passing through conc. H₂SO₄.

Q2. Explain the physical properties of hydrogen chloride gas.

Ans:

• Colour: Colourless

• Odour: Pungent, irritating

• Taste: Sour

• Solubility: Highly soluble in water

• Density: Heavier than air

• Nature: Acidic

• Liquefaction: Easily liquefied under pressure

• Toxicity: Toxic in high concentrations

Q3. Explain the chemical properties of hydrogen chloride gas.

Ans:

1. Acidic nature: Turns blue litmus red.

2. With ammonia: NH₃ + HCl → NH₄Cl (white fumes)

3. With metals: Zn + 2HCl → ZnCl₂ + H₂

4. With metal carbonates: Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂

5. With metal oxides: CuO + 2HCl → CuCl₂ + H₂O

6. With metal hydroxides: NaOH + HCl → NaCl + H₂O

Q4. What is hydrochloric acid? Write its properties and uses.

Ans:
Hydrochloric acid is an aqueous solution of HCl gas.

Properties:

• Strong monobasic acid

• Colourless, corrosive liquid

• Conducts electricity

• pH < 7

Uses:

1. Preparation of chlorine gas

2. Manufacture of PVC

3. Pickling of steel

4. Production of dyes and drugs

5. Laboratory reagent

6. Digestion of food in the stomach

Q5. Describe the tests for hydrogen chloride gas.

Ans:

1. Litmus test: Turns blue litmus red.

2. Ammonia test: White fumes with NH₄OH.

3. Silver nitrate test: White precipitate of AgCl.

4. Moist blue litmus: Turns red.

Q6. Write the reaction of HCl with:

(a) Zn (b) Na₂CO₃ (c) CuO (d) NaOH (e) NH₃
Ans:
(a) Zn + 2HCl → ZnCl₂ + H₂
(b) Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂
(c) CuO + 2HCl → CuCl₂ + H₂O
(d) NaOH + HCl → NaCl + H₂O
(e) NH₃ + HCl → NH₄Cl

Q7. Explain the industrial preparation of hydrochloric acid.

Ans:
Industrially, HCl is prepared by:

1. Direct combination: H₂ + Cl₂ → 2HCl (in sunlight)

2. By-product method: During chlorination of organic compounds.
   The gas is dissolved in water to form hydrochloric acid.

Q8. Why is HCl gas not collected over water?

Ans:
HCl gas is highly soluble in water, so it cannot be collected over water. It is collected by upward displacement of air because it is heavier than air.

Q9. What is the role of HCl in the human body?

Ans:

• Digestion: HCl provides an acidic medium for the action of enzymes like pepsin.

• Kills bacteria: It kills harmful bacteria present in food.

• Activates enzymes: It activates pepsinogen to pepsin.

Q10. Write the reaction of HCl with:

(a) CaCO₃ (b) Mg (c) Fe (d) Al
Ans:
(a) CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂
(b) Mg + 2HCl → MgCl₂ + H₂
(c) Fe + 2HCl → FeCl₂ + H₂
(d) 2Al + 6HCl → 2AlCl₃ + 3H₂

Q11. Explain the drying of HCl gas.

Ans:
HCl gas is dried by passing through concentrated sulphuric acid (H₂SO₄). It cannot be dried using quicklime (CaO) or caustic soda (NaOH) because they react with HCl.

Q12. What is the action of HCl on:

(a) Blue litmus (b) Sodium hydroxide (c) Silver nitrate
Ans:
(a) Turns red
(b) NaOH + HCl → NaCl + H₂O (Neutralisation)
(c) AgNO₃ + HCl → AgCl↓ + HNO₃ (White precipitate)

Q13. Write the difference between HCl gas and hydrochloric acid.

Ans:

Q14. Explain the preparation of hydrochloric acid from HCl gas.

Ans:
HCl gas is dissolved in water to form hydrochloric acid. The process is highly exothermic. The gas is passed through water, and the resulting solution is hydrochloric acid.

Q15. Write any five uses of hydrochloric acid.

Ans:

1. Preparation of chlorine gas

2. Manufacture of PVC

3. Pickling of steel

4. Production of dyes and drugs

5. Laboratory reagent

6. Digestion of food

🎯 Exam Tips for Class 10 ICSE Chemistry Students

🧪 Understand the preparation methods — laboratory and industrial

📝 Memorise all chemical equations — they are frequently asked

🔬 Practise diagram-based questions for full marks

📊 Learn the tests for HCl gas — litmus, ammonia, silver nitrate

✅ Revise uses of HCl in daily life and industry

🔗 Connect concepts to real-life applications like digestion and PVC manufacturing

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