Questions on Reactants and Products
Multiple-Choice Questions – Reactants and Products
1. In a chemical reaction, the substances that start the reaction are called:
A) Products
B) Catalysts
C) Reactants
D) Enzymes
E) Compounds
2. What are products in a chemical reaction?
A) Substances that are added to make the reaction faster
B) Substances formed as a result of the reaction
C) Substances that absorb heat
D) Substances broken into atoms
E) Substances that dissolve in water
3. In the reaction: 2H₂ + O₂ → 2H₂O, what are the reactants?
A) H₂ and H₂O
B) O₂ and H₂O
C) H₂ and O₂
D) H₂O and O
E) O₂ and HO
4. In the same reaction (2H₂ + O₂ → 2H₂O), what is the product?
A) H₂
B) O₂
C) H₂O
D) H
E) OH
5. In a chemical equation, reactants are always written:
A) On the right side of the arrow
B) Below the arrow
C) After the products
D) On the left side of the arrow
E) In parentheses
6. The arrow (→) in a chemical equation means:
A) Equal to
B) Reversed
C) Yields or produces
D) Added to
E) Mixed with
7. In the reaction: CH₄ + 2O₂ → CO₂ + 2H₂O, which are the products?
A) CH₄ and O₂
B) CO₂ and H₂O
C) O₂ and H₂
D) CH₄ and H₂O
E) CO₂ and CH₄
8. Which of the following best describes the difference between reactants and products?
A) Products are consumed; reactants are formed
B) Reactants are always solids; products are gases
C) Reactants start the reaction; products are formed by the reaction
D) Products are always liquids; reactants are solids
E) Reactants are produced after the reaction
9. In a balanced chemical reaction, what is true about the number of atoms on both sides?
A) There are fewer atoms among the products
B) There are more atoms among the reactants
C) The number of atoms is equal on both sides
D) Atoms are only counted on the reactant side
E) Atoms disappear on the product side
10. In the reaction: Zn + 2HCl → ZnCl₂ + H₂, the products are:
A) Zn and HCl
B) Zn and H₂
C) ZnCl₂ and H₂
D) ZnCl₂ and HCl
E) Zn and Cl₂
11. Which of these indicates a chemical reaction has occurred?
A) Formation of new products
B) Change in shape
C) Melting
D) Freezing
E) Evaporation
12. In the reaction: CaCO₃ → CaO + CO₂, what is the reactant?
A) CaCO₃
B) CaO
C) CO₂
D) Ca
E) O₂
13. What type of change results in the formation of products from reactants?
A) Physical change
B) Mechanical change
C) Electrical change
D) Chemical change
E) Nuclear change
14. In chemical reactions, what happens to reactants?
A) They dissolve
B) They are converted into products
C) They disappear
D) They expand
E) They change shape only
15. In photosynthesis, the reactants are:
A) Glucose and oxygen
B) Carbon dioxide and water
C) Water and glucose
D) Sunlight and sugar
E) Oxygen and nitrogen
16. In a chemical equation, what symbol separates the reactants from the products?
A) +
B) =
C) →
D) ⇌
E) :
17. Which of the following correctly represents a chemical equation with reactants and products?
A) H₂O → H₂ + O
B) H₂O + H → H₂
C) H₂ + O₂ = H₂O
D) H₂ + O₂ → H₂O
E) H + H + O → O₂H
18. In a combustion reaction, common reactants include:
A) Water and carbon dioxide
B) Oxygen and a hydrocarbon
C) Hydrogen and helium
D) Carbon and nitrogen
E) Sulfur and sodium
19. What is the role of reactants in a chemical reaction?
A) They are unchanged
B) They speed up the reaction
C) They are consumed to form products
D) They change the temperature
E) They are catalysts
20. Which of the following is NOT a typical product of combustion?
A) CO₂
B) H₂O
C) CH₄
D) Heat
E) Light
21. Which process involves reactants forming completely new substances?
A) Freezing
B) Melting
C) Evaporation
D) Chemical reaction
E) Condensation
22. What is required for a chemical reaction to occur?
A) Presence of water
B) Only high pressure
C) Rearrangement of atoms in reactants
D) Change in temperature only
E) Reaction with light only
23. The law of conservation of mass states:
A) Products always weigh more than reactants
B) Reactants are heavier than products
C) Mass is lost during a reaction
D) Mass is neither created nor destroyed in a reaction
E) Mass doubles after a reaction
24. In the reaction: 2K + Cl₂ → 2KCl, the products are:
A) K and Cl
B) KCl and Cl
C) K and KCl
D) KCl
E) Cl₂
25. What are the physical states of reactants and products usually indicated by in equations?
A) Numbers
B) Symbols like (s), (l), (g), (aq)
C) Arrows
D) Parentheses
E) Chemical names
26. Which of the following is true about products?
A) They are used up in the reaction
B) They are unchanged
C) They are always gases
D) They are formed as a result of a reaction
E) They are the same as reactants
27. A chemical reaction has taken place when:
A) A new substance with different properties is formed
B) Ice melts
C) Water evaporates
D) A solid is broken into smaller pieces
E) Steam condenses
28. What determines the identity of products in a reaction?
A) The number of electrons
B) The color of reactants
C) The properties of reactants
D) The amount of heat
E) The phase of matter
29. In the reaction: N₂ + 3H₂ → 2NH₃, what is the product?
A) N₂
B) H₂
C) NH₃
D) NH₄
E) N₂H₄
30. Which of the following reactions has carbon dioxide as a product?
A) H₂ + O₂ → H₂O
B) CH₄ + 2O₂ → CO₂ + 2H₂O
C) Na + Cl₂ → NaCl
D) HCl + NaOH → NaCl + H₂O
E) NH₃ + HCl → NH₄Cl
- Questions on Chemical Change
- Questions on Chemical Symbols and Formulas
- Questions on Chemical Properties
Answer Key with Explanations
1. C) Reactants are substances that begin a chemical reaction.
2. B) Products are the new substances formed.
3. C) Hydrogen (H₂) and oxygen (O₂) are the reactants.
4. C) Water (H₂O) is the product.
5. D) Reactants appear on the left.
6. C) The arrow means "yields" or "produces."
7. B) CO₂ and H₂O are the products.
8. C) Reactants initiate the reaction; products are formed.
9. C) Atom count is balanced on both sides.
10. C) Zinc chloride and hydrogen gas are the products.
11. A) A new product shows a chemical reaction occurred.
12. A) CaCO₃ is the starting substance—reactant.
13. D) Chemical change forms new substances.
14. B) Reactants become products.
15. B) Photosynthesis uses carbon dioxide and water.
16. C) → separates reactants from products.
17. D) H₂ + O₂ → H₂O is correct.
18. B) Combustion uses hydrocarbons and oxygen.
19. C) Reactants are used to make products.
20. C) Methane (CH₄) is a reactant, not a product.
21. D) Chemical reactions make new substances.
22. C) Atoms in reactants must rearrange.
23. D) Mass is conserved during reactions.
24. D) Potassium chloride is the product.
25. B) States are labeled as (s), (l), (g), or (aq).
26. D) Products are formed after the reaction.
27. A) Chemical change produces a new substance.
28. C) Product identity depends on reactants’ properties.
29. C) Ammonia (NH₃) is the product.
30. B) Methane combustion produces CO₂.
Share Online!
