Class 8 General Science Notes - Unit-6- Chemical Reaction and Bonding ( Solved Exercise MCQs)

Unit-6- Chemical Reaction and Bonding ( Solved Exercise MCQs)

(National Book Foundation - New Book/New Syllabus Based on National Curriculum Pakistan 2023-2024 and Onwards)

(Class 8 General Science Notes for 8th Centralized Exam 2023-2024 and onward, FDE, Islamabad)

A. MCQs (Choose the Correct Answers).

1. Which of the following groups contains alkali metals?

a. Il A
b. VII A
c. III A
d. I A

... Answer is a. I A
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2. The reaction between sodium and water produces

a. H₂
b. 0₂
c. NaCl
d. Na₂Co₃

... Answer is d. H₂
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3. Photosynthesis in green plants is

a. synthesis.
b. decomposition
c. combustion.
d. endothermic.

... Answer is d.  endothermic
-----------------

4. Which substance indicates the reaction has taken place?

a. Mg
b. HCI
c. H₂
d. MgCI₂

... Answer is c.  H₂
---------------

5. Which of the following reactions is unbalanced?

a. C(g) + O₂(g) → CO₂(8)
b. H₂(g) + Cl₂(g) →2HCl(g)
c. KCIO₃(s) → KCl(g) + O₂(g)
d. Ca(s) + S(s) → CaS (s)

... Answer is c.  KCIO₃(s) → KCl(g) + O₂(g)
-----------------

6. An endothermic reaction occurs when

a. carbon burns in air.
b. electrical discharges in the atmosphere nitrogen combines with oxygen.
c. natural gas burns in air.
d. hydrogen combines with oxygen to form water.

... Answer is b.  electrical discharges in the atmosphere nitrogen combines with oxygen.
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7. Which of the following is not a chemical reaction?

a. Rusting
b. Frying an egg
c. Photosynthesis
d. Melting of ice

... Answer is d.  Melting of ice
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8. When copper sulphate solution is mixed with sodium hydroxide solution, the chemical reaction is indicated by:

a. Emission of a gas
b. Odour change
c. Temperature change
d. Formation of precipitate

... Answer is d.  Formation of precipitate
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9. What happens when few drops of iodine solution is added in starch solution?

a. Gas is emitted
b. Precipitates are formed
c. Colour change occurs
d. Bad odour is emitted

... Answer is c.  Colour change occurs
---------------

10. Which of the following is not a balanced chemical reaction?

a. H₂(g) + Cl₂(g) →2HCl(g)
b. H₂(g) + O₂(9) →2H₂O(l)
c. C(s) + O₂(s) → CO₂(g)
d. 2NH₃(g) N₂(g) +3H₂(g)

... Answer is b.  H₂(g) + O₂(9) →2H₂O(l)
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