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Vidaara.orgClass 10 · Chemistry
CodeVID-C10-01-T2-01
Assignment — Types of Chemical Reactions
Chapter: Chemical Reactions and Equations
Topic: Types of Chemical Reactions
Maximum Marks: 30
Time: 60 minutes
Name: ____________________ Roll No.: __________ Date: ____________

General Instructions

  • All questions are compulsory.
  • Section A carries 1 mark each, Section B 2 marks, Section C 3 marks and Section D 5 marks.
  • Show all working for Sections B, C and D. Only final answers are given at the end — for full solutions, raise your doubts with your teacher.
Section A — Multiple Choice Questions 5 × 1 = 5 marks
1.
A + B → AB represents a:
  • A.decomposition reaction
  • B.combination reaction
  • C.displacement reaction
  • D.double displacement reaction
2.
Thermal decomposition of CaCO3 gives CaO and:
  • A.O2
  • B.CO
  • C.CO2
  • D.C
3.
Which metal can displace copper from copper sulphate?
  • A.silver
  • B.gold
  • C.zinc
  • D.platinum
4.
The white precipitate formed when Na2SO4 and BaCl2 solutions mix is:
  • A.NaCl
  • B.BaSO4
  • C.BaCl2
  • D.Na2SO4
5.
Decomposition reactions are usually:
  • A.exothermic
  • B.endothermic
  • C.neither
  • D.always explosive
Section B — Short Answer (2 marks) 3 × 2 = 6 marks
6.
Distinguish between a combination and a decomposition reaction with one example each.
7.
Why is the slaking of lime (CaO + H2O) called an exothermic combination reaction?
8.
Give one example each of a thermal and an electrolytic decomposition.
Section C — Short Answer (3 marks) 2 × 3 = 6 marks
9.
Explain, with a balanced equation, what is observed when zinc is added to copper sulphate solution.
10.
Write balanced equations for any two precipitation reactions and underline the precipitate in each.
Section D — Long Answer (5 marks) 1 × 5 = 5 marks
11.
Name the four main types of chemical reactions. For each, give the general form, one balanced example, and state whether it is normally exothermic or endothermic where relevant.

Answer Key

Section A — Multiple Choice Questions
  1. (B) combination reaction
  2. (C) CO2
  3. (C) zinc
  4. (B) BaSO4
  5. (B) endothermic
Section B — Short Answer (2 marks)
  1. Combination: two or more reactants form one product, e.g. C + O₂ → CO₂. Decomposition: one compound splits into simpler ones, e.g. CaCO₃ → CaO + CO₂.
  2. Two substances combine to form a single product, Ca(OH)₂ (combination), and a large amount of heat is released during the reaction (exothermic).
  3. Thermal: CaCO₃ → CaO + CO₂ (heat). Electrolytic: 2H₂O → 2H₂ + O₂ (electricity).
Section C — Short Answer (3 marks)
  1. Zinc is more reactive than copper, so it displaces copper: Zn + CuSO₄ → ZnSO₄ + Cu. The blue colour fades as Cu²⁺ is replaced by colourless Zn²⁺, and a reddish-brown copper deposit appears.
  2. Pb(NO₃)₂ + 2KI → PbI₂ (precipitate) + 2KNO₃; Na₂SO₄ + BaCl₂ → BaSO₄ (precipitate) + 2NaCl.
Section D — Long Answer (5 marks)
  1. 1) Combination (A + B → AB), e.g. CaO + H₂O → Ca(OH)₂, usually exothermic. 2) Decomposition (AB → A + B), e.g. CaCO₃ → CaO + CO₂, usually endothermic. 3) Displacement (A + BC → AC + B), e.g. Fe + CuSO₄ → FeSO₄ + Cu, often exothermic. 4) Double displacement (AB + CD → AD + CB), e.g. Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl (precipitation); neutralisation HCl + NaOH → NaCl + H₂O is exothermic.
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