Chapter 2 - Acid, Bases and Salts
CBSE CLASS X – BOARD
MODEL EXAMINATION (2026-27)
SCIENCE
(CHEMISTRY) — CHAPTER 2: ACIDS, BASES AND SALTS
(Strictly Based on CBSE Board Pattern & NCERT
Textbook)
|
Time Allowed: 1 Hour 30 Minutes |
Maximum Marks: 40 |
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General Instructions:
1. This question paper
consists of 18 questions in 5 Sections (A, B, C, D, and E).
2. Section A comprises 8
Multiple Choice Questions (Q1 to Q8) of 1 mark each, including 2
Assertion-Reason questions.
3. Section B comprises 4
Very Short Answer (VSA) type questions (Q9 to Q12) of 2 marks each.
4. Section C comprises 3
Short Answer (SA) type questions (Q13 to Q15) of 3 marks each.
5. Section D comprises 2
Long Answer (LA) type questions (Q16 & Q17) of 5 marks each with internal
choice.
6. Section E comprises 1
Case-Based Question (Q18) of 4 marks with internal choice in sub-question
(iii).
7. All questions are
compulsory. Internal choices are provided in Sections D and E.
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SECTION A (8 Marks) — Multiple Choice
Questions [1 Mark Each] |
1. Which of the following statements is correct regarding the reaction
of granulated zinc with sodium hydroxide?
|
(a) Hydrogen gas is
evolved and sodium zincate (Na₂ZnO₂) is formed. |
(b) Oxygen gas is
evolved and zinc hydroxide is formed. |
|
(c) No reaction
takes place as zinc does not react with bases. |
(d) Sodium hydride
and zinc oxide are formed. |
2. A solution reacts with crushed eggshells to give a gas that turns
lime water milky. The solution contains:
|
(a) NaCl |
(b) HCl |
|
(c) LiCl |
(d) KCl |
3. Which of the following substances can be used as an olfactory
indicator in a science laboratory?
|
(a) Phenolphthalein |
(b) Methyl orange |
|
(c) Clove oil |
(d) Litmus extract |
4. During the preparation of hydrogen chloride gas on a humid day, the
gas is passed through a guard tube containing calcium chloride. The role of
calcium chloride is to:
|
(a) Absorb the
evolved HCl gas |
(b) Moist the gas |
|
(c) Absorb moisture
from the gas |
(d) Neutralise
basic impurities |
5. Tooth enamel is made up of a crystalline form of calcium phosphate
called calcium hydroxyapatite. Tooth decay begins when the pH of the mouth
falls below:
|
(a) 7.0 |
(b) 6.5 |
|
(c) 5.5 |
(d) 8.0 |
6. In the chlor-alkali process, the gases liberated at the anode and the
cathode respectively are:
|
(a) H₂ and Cl₂ |
(b) Cl₂ and H₂ |
|
(c) Cl₂ and O₂ |
(d) O₂ and H₂ |
7. Assertion (A): Aqueous solutions of glucose and alcohol do not
conduct electricity, while dilute HCl conducts electricity.
Reason (R): Glucose and alcohol do not ionise in water to produce free H⁺
(hydronium) ions.
Choose the correct option:
(a) Both (A) and (R) are
true and (R) is the correct explanation of (A).
(b) Both (A) and (R) are
true but (R) is NOT the correct explanation of (A).
(c) (A) is true but (R) is
false.
(d) (A) is false but (R) is
true.
8. Assertion (A): While diluting concentrated sulphuric acid, water
should never be added directly to the acid.
Reason (R): The dilution process is highly endothermic and absorbs a huge
amount of heat from surroundings.
Choose the correct option:
(a) Both (A) and (R) are
true and (R) is the correct explanation of (A).
(b) Both (A) and (R) are
true but (R) is NOT the correct explanation of (A).
(c) (A) is true but (R) is
false.
(d) (A) is false but (R) is
true.
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SECTION B (8 Marks) — Very Short Answer
Type Questions [2 Marks Each] |
|
9. A milkman adds a very small amount of baking soda to
fresh milk. |
[2] |
|
10. Why does dry HCl gas not change the colour of dry blue
litmus paper, whereas moist blue litmus paper turns red when exposed to it?
Write the relevant chemical equation. |
[2] |
|
11. Five solutions A, B, C, D, and E when tested with
universal indicator show pH values of 4, 1, 11, 7, and 9 respectively. |
[2] |
|
12. Write the chemical name and formula of Plaster of
Paris. Why should it always be stored in a moisture-proof container? |
[2] |
|
SECTION C (9 Marks) — Short Answer Type
Questions [3 Marks Each] |
|
13. Equal lengths of magnesium ribbons are taken in test
tubes A and B. Hydrochloric acid (HCl) is added to test tube A, while acetic
acid (CH₃COOH) of the same concentration is added to test tube B. |
[3] |
|
14. (a) What is meant by 'water of crystallisation'? |
[3] |
|
15. A metal carbonate 'X' on reacting with an acid produces
a gas 'Y' which turns lime water milky. If excess of gas 'Y' is passed
through lime water, the milkiness disappears due to formation of 'Z'. |
[3] |
|
SECTION D (10 Marks) — Long Answer Type
Questions [5 Marks Each] |
16. (a) What is the
chlor-alkali process? Why is it named so? Write the balanced chemical equation
for the reaction involved.
(b) Name the gases liberated at the anode and the cathode during this process,
and write one important industrial use of each.
(c) Write one important use of the chemical solution formed near the cathode.
[2 + 2 + 1 = 5 Marks]
― OR ―
16. [OR] (a) A compound 'P'
of sodium is used in the kitchen for making crispy pakoras and is also an
ingredient in antacids.
(i) Identify 'P' and write its
chemical formula and chemical name.
(ii) How is 'P' prepared from sodium
chloride? Write the balanced chemical equation.
(iii) What happens when 'P' is heated
during cooking? Write the equation.
(b) How is washing soda obtained from compound 'P'? Write its chemical formula
and one industrial use.
[3 + 2 = 5 Marks]
17. Explain the importance
of pH in everyday life with respect to each of the following:
(a) Human digestive system during indigestion and how antacids work.
(b) Cause and prevention of tooth decay in human mouth.
(c) Self-defence mechanisms in honeybees, ants, and nettle plants, along with
their remedies.
(d) Survival of aquatic life during acid rain events.
[1.5 + 1 + 1.5 + 1 = 5 Marks]
― OR ―
17. [OR] (a) What is
bleaching powder? How is it manufactured? Write the balanced chemical equation.
(b) Write two important uses of bleaching powder.
(c) A baker found that the cake baked by him was hard and small in size. Which
ingredient did he forget to add? Explain the role of this ingredient with
chemical equations.
[2 + 1 + 2 = 5 Marks]
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SECTION E (4 Marks) — Case-Based /
Passage-Based Question [4 Marks] |
18. Case Study: Investigation of Salt Hydrolysis
and pH Nature
A science teacher provided four
unlabeled test tubes containing 0.1 M aqueous solutions of four different
salts: Sodium Chloride (NaCl), Ammonium Chloride (NH₄Cl), Sodium Acetate
(CH₃COONa), and Sodium Carbonate (Na₂CO₃) to students for laboratory analysis.
The students tested each solution with blue litmus paper, red litmus paper, and
universal indicator paper to measure their approximate pH values and deduce the
nature of the parent acid and parent base for each salt.
Based on your understanding of salts and pH, answer the following questions:
|
(i) Which of the
given salt solutions will turn red litmus paper blue? State its pH range (pH
> 7 or pH < 7). |
[1] |
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(ii) Identify the
acidic salt among the four and name the parent acid and base from which it is
formed. |
[1] |
|
(iii) Explain why
an aqueous solution of sodium chloride (NaCl) is neutral to litmus paper,
while an aqueous solution of sodium carbonate (Na₂CO₃) is basic in nature. |
[2] |
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