Chemical Reactions Quiz - ICSE Class 8 Science

Free practice quiz: Chemical Reactions (ICSE Class 8 Science). 50 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

This ICSE Class 8 Science practice quiz has 50 multiple-choice questions on Chemical Reactions, and 50 of them come with an explanation. Try the 5 sample questions below (tap an option to check yourself), then play the full quiz online. No sign-up needed.

Sample questions

1. Which of the following describes an exothermic reaction?

   1. A reaction that absorbs heat from the surroundings.
   2. A reaction that releases heat into the surroundings.
   3. A reaction that involves the transfer of electrons.
   4. A reaction that forms a precipitate.
   Show answer

   Answer: B. A reaction that releases heat into the surroundings.

   Exothermic reactions are chemical reactions that emit energy, usually in the form of heat, light, or sound. Endothermic reactions, on the other hand, absorb heat from the surroundings.

2. Which of the following is a characteristic of a reversible reaction?

   1. It proceeds to completion, forming only products.
   2. It can proceed in both forward and backward directions.
   3. It always releases energy.
   4. It requires a catalyst to occur.
   Show answer

   Answer: B. It can proceed in both forward and backward directions.

   Reversible reactions are reactions that can occur in both the forward (reactants to products) and backward (products to reactants) directions. They reach a state of equilibrium where the rates of the forward and reverse reactions are equal.

3. What is the primary role of enzymes in biological chemical reactions?

   1. To increase the activation energy.
   2. To provide energy for the reaction.
   3. To act as catalysts, speeding up reactions.
   4. To bind to reactants permanently.
   Show answer

   Answer: C. To act as catalysts, speeding up reactions.

   Enzymes are biological catalysts, which are proteins that speed up specific chemical reactions in living organisms by lowering the activation energy required for the reaction to occur.

4. When zinc reacts with dilute sulfuric acid, the products are zinc sulfate and hydrogen gas. This is an example of a:

   1. Combination reaction
   2. Decomposition reaction
   3. Single displacement reaction
   4. Neutralization reaction
   Show answer

   Answer: C. Single displacement reaction

   The reaction Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g) shows that zinc (a metal) displaces hydrogen (from the acid) to form zinc sulfate and hydrogen gas. This is characteristic of a single displacement reaction.

5. What is the primary product when copper reacts with excess oxygen at high temperatures?

   1. Copper (I) oxide (Cu₂O)
   2. Copper (II) oxide (CuO)
   3. Copper sulfate (CuSO₄)
   4. Copper chloride (CuCl₂)
   Show answer

   Answer: B. Copper (II) oxide (CuO)

   Copper reacts with oxygen at high temperatures to form copper(II) oxide. The reaction is $2Cu(s) + O_2(g) ightarrow 2CuO(s)$. Copper(I) oxide is formed under different conditions.

More questions in this quiz

Answers and explanations are in the full quiz.

1. In a balanced chemical equation, the law of conservation of mass states that:
2. Combustion is a chemical reaction that:
3. When iron filings are heated strongly in the presence of oxygen, what is the primary product formed?
4. Which of the following is an example of a decomposition reaction?
5. What is the primary function of a catalyst in a chemical reaction?
6. The reaction between an acid and a base is known as neutralization. What are the typical products of a neutralization reaction?
7. Which of the following chemical reactions represents a displacement reaction?
8. When carbon burns in limited supply of oxygen, it forms:
9. Photosynthesis is a process that converts light energy into chemical energy. Which type of chemical reaction best describes it?
10. The reaction between sodium chloride (NaCl) and silver nitrate (AgNO₃) produces a white precipitate. What is this precipitate?
11. What is the term used for a reaction that absorbs energy from its surroundings?
12. In the reaction Zn + 2HCl → ZnCl₂ + H₂, what is being oxidized?
13. Which of the following is a sign that a chemical reaction has occurred?
14. Decomposition of calcium carbonate (CaCO₃) upon heating produces:
15. What is the process called when a gas turns into a liquid?
16. Which of the following pairs of reactants will undergo a double displacement reaction?
17. When electricity is passed through molten aluminum oxide (Al₂O₃) in the Hall-Héroult process, what is produced at the cathode?
18. A reaction that is spontaneous under given conditions is typically:
19. If a reaction produces more heat than it absorbs, it is:
20. The formation of rust on iron is a chemical reaction known as:
21. In a single displacement reaction, a more reactive metal will displace a less reactive metal from its:
22. Which of the following is an example of an acid-base reaction that does NOT produce water?
23. The process of breaking down a compound using electricity is called:
24. What is the term for a reaction where two or more reactants combine to form a single product?
25. When a substance reacts with oxygen and releases heat and light, it is undergoing:
26. The balanced chemical equation for the reaction between magnesium and oxygen is $2Mg + O₂ → 2MgO$. What type of reaction is this?
27. What does the law of definite proportions state about a chemical compound?
28. The reaction $H_2O_2 ightarrow H_2O + O_2$ is balanced. If you start with 2 moles of $H_2O_2$, how many moles of $O_2$ are produced?
29. What is the term for a reaction that occurs at a very slow rate, such as the rusting of iron?
30. Which gas is produced during the electrolysis of acidified water?
31. The reaction $SO_2 + O_2 ightarrow SO_3$ is an example of:
32. In the reaction $AgNO_3 + NaCl ightarrow AgCl \downarrow + NaNO_3$, the arrow pointing down ($\downarrow$) indicates:
33. The chemical process by which plants convert light energy into chemical energy is called:
34. Which of the following is NOT a factor that affects the rate of a chemical reaction?
35. What is the term for a reaction where heat is absorbed from the surroundings?
36. The balanced equation for the reaction of hydrogen gas and chlorine gas to form hydrogen chloride is $H_2 + Cl_2 ightarrow 2HCl$. If 1 mole of $H_2$ reacts completely, how many moles of $HCl$ are produced?
37. Which law states that for a given chemical reaction, the heat evolved or absorbed is the same whether the reaction takes place in one step or in several steps?
38. The reaction between a metal and an acid typically produces:
39. What is the term for a chemical reaction that proceeds in the reverse direction as well?
40. When sodium bicarbonate (NaHCO₃) is heated, it decomposes to produce sodium carbonate (Na₂CO₃), water (H₂O), and carbon dioxide (CO₂). This is an example of:
41. What is the role of a catalyst in a reversible reaction at equilibrium?
42. The process where a solid changes directly into a gas is called:
43. When copper sulfate solution is electrolyzed using inert electrodes, what happens at the anode?
44. What is the term for a reaction that releases energy into its surroundings?
45. The reaction $CO_2 + Ca(OH)_2 ightarrow CaCO_3 + H_2O$ is an example of:

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