10th LBA | Acids Bases And Salts

MG SCHOOL SCIENCE

Unit Test Examination

Class 10 – Science

Chapter 2: Acids, Bases and Salts

Question Paper with Key Answers

Student Name:

Register Number:

Class / Section:

Date:

Time: 1 Hour Maximum Marks: 25

General Instructions:

1. All questions are compulsory.
2. Write answers neatly and clearly.
3. Draw neat, labelled diagrams wherever necessary.
4. Write balanced chemical equations wherever required.
5. Marks are indicated against each question.

SECTION – A: MULTIPLE CHOICE QUESTIONS (5 × 1 = 5 Marks)

1 Mark 1. Which of the following represents a neutralisation reaction?

(A) BaCl₂ + H₂SO₄ → BaSO₄ + 2HCl (B) MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂ (C) 2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O (D) AgNO₃ + HCl → AgCl + HNO₃

1 Mark 2. A compound that reacts with both acids and bases to produce salt and water is:

(A) Aluminium oxide (B) Copper oxide (C) Iron oxide (D) Sodium oxide

1 Mark 3. The gas liberated when sodium carbonate reacts with dilute hydrochloric acid is:

(A) Carbon dioxide (B) Nitrogen dioxide (C) Hydrogen (D) Chlorine

1 Mark 4. The compound used to remove permanent hardness of water is:

(A) Sodium carbonate (B) Sodium hydroxide (C) Sodium hydrogen carbonate (D) Sodium chloride

1 Mark 5. The molecular formula of lime water is:

(A) CaO (B) Ca(OH)₂ (C) CaCO₃ (D) CO₂

SECTION – B: ONE-MARK QUESTIONS (4 × 1 = 4 Marks)

1 Mark 6. What is a neutralisation reaction?

1 Mark 7. What are alkalis?

1 Mark 8. Which ion is responsible for the acidic nature of an aqueous solution?

1 Mark 9. What is the chemical name of bleaching powder?

SECTION – C: TWO-MARK QUESTIONS (3 × 2 = 6 Marks)

2 Marks 10. Give scientific reason: While diluting an acid, the acid should be added to water and not water to acid.

2 Marks 11. The pH values of three solutions A, B and C are 5, 6 and 7 respectively.
(a) Which solution is the most acidic?
(b) Which solution is neutral?

2 Marks 12. Write any two chemical properties of acids.

SECTION – D: THREE-MARK QUESTIONS (2 × 3 = 6 Marks)

3 Marks 13. Draw the diagram of arrangement of the apparatus to show the reaction of zinc granules with dilute sulphuric acid and testing hydrogen gas by burning. Label the parts given below:

(i) Zinc granules
(ii) Soap solution

Reference: Arrangement of apparatus

Schematic reference diagram – redraw neatly in the answer sheet.

3 Marks 14. What is a strong acid? Explain how tooth decay is caused. How can it be prevented?

SECTION – E: FOUR-MARK QUESTION (1 × 4 = 4 Marks)

4 Marks 15. What is the chlor-alkali process? Name the three products obtained during this process and write one use of each product.

***** END OF QUESTION PAPER *****

ANSWER KEY AND MARKING SCHEME

Class 10 Science – Acids, Bases and Salts

SECTION A – MCQ ANSWERS (5 Marks)

1. (C) 2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O

2. (A) Aluminium oxide.

3. (A) Carbon dioxide.

4. (A) Sodium carbonate.

5. (B) Ca(OH)₂.

SECTION B – ONE-MARK ANSWERS (4 Marks)

6. Neutralisation reaction:
The reaction between an acid and a base produces salt and water.

7. Alkalis:
Bases that dissolve in water are called alkalis.

8. Acidic ion:
Hydrogen ion (H⁺) or hydronium ion (H₃O⁺).

9. Chemical name of bleaching powder:
Calcium oxychloride (CaOCl₂).

SECTION C – TWO-MARK ANSWERS (6 Marks)

10. Why should acid be added to water?
Dilution of concentrated acids is highly exothermic. If water is added to concentrated acid, the heat produced may cause the mixture to splash out and cause burns. Therefore, acid should be added slowly to water with continuous stirring.

11. pH values:
(a) Solution A (pH 5) is the most acidic because it has the lowest pH value.
(b) Solution C (pH 7) is neutral.

12. Any two chemical properties of acids:

1. Acids react with metals to produce salt and hydrogen gas.
2. Acids react with bases to produce salt and water.

Equations:

Zn + H₂SO₄ → ZnSO₄ + H₂

HCl + NaOH → NaCl + H₂O

SECTION D – THREE-MARK ANSWERS (6 Marks)

13. Zinc granules and dilute sulphuric acid experiment:

Labels:

1. Zinc granules
2. Soap solution

Reaction:

Zn + H₂SO₄ → ZnSO₄ + H₂ ↑

Explanation:

1. Zinc granules react with dilute sulphuric acid and produce zinc sulphate and hydrogen gas.
2. The hydrogen gas is passed through soap solution, forming bubbles.
3. When the hydrogen-filled bubbles are ignited, they burn with a characteristic pop sound.

Note: The pop sound confirms the presence of hydrogen gas. The experiment should be performed under teacher supervision, away from the acid apparatus, using small quantities of gas.

14.
Acids that produce more H⁺ ions are called strong acids. After eating food, bacteria in the mouth decompose the remaining sugar and food particles, producing acids The best way to prevent this is to clean the mouth after eating

SECTION E – FOUR-MARK ANSWER (4 Marks)

15. Chlor-alkali process and its products:
The electrolysis of an aqueous solution of sodium chloride (brine) is called the chlor-alkali process.

Balanced chemical equation:

2NaCl + 2H₂O → 2NaOH + H₂ + Cl₂

Three products and their uses:

1. Sodium hydroxide (NaOH): Used in making soaps and detergents.
2. Hydrogen (H₂): Used as a fuel and in the manufacture of ammonia.
3. Chlorine (Cl₂): Used for disinfecting drinking water.

TOTAL: 25 / 25 MARKS

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