Questions on Redox Reactions and Molecular Compounds
Multiple-Choice Questions – Redox Reactions and Molecular Compounds
1. What defines a molecular compound?
A) A compound made only of metals
B) A compound held together by ionic bonds
C) A compound formed by sharing electrons between nonmetals
D) A compound with high electrical conductivity
E) A compound that always forms ions in water
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2. Which of the following is a molecular compound?
A) NaCl
B) MgO
C) CO₂
D) KBr
E) CaCl₂
3. Which of the following is not true about molecular compounds?
A) They usually have low melting points
B) They consist of molecules
C) They conduct electricity in solution
D) They are formed by covalent bonding
E) They are generally gases or liquids at room temperature
4. In redox reactions, oxidation is defined as:
A) Gain of electrons
B) Loss of electrons
C) Gain of neutrons
D) Loss of protons
E) No change in oxidation state
5. In a redox reaction involving molecular compounds, which element is oxidized in the reaction: CH₄ + 2O₂ → CO₂ + 2H₂O?
A) Carbon
B) Hydrogen
C) Oxygen
D) Water
E) Methane
6. What happens to the oxidation number of oxygen in the reaction: H₂ + O₂ → H₂O?
A) It increases
B) It stays the same
C) It decreases
D) It becomes zero
E) It becomes positive
7. What kind of bond exists in molecular compounds?
A) Ionic bond
B) Metallic bond
C) Covalent bond
D) Hydrogen bond
E) Network bond
8. Which of the following is both a molecular compound and involved in redox chemistry?
A) H₂O
B) NaCl
C) FeCl₃
D) MgO
E) KBr
9. In the redox reaction: H₂ + Cl₂ → 2HCl, what is the reducing agent?
A) H₂
B) Cl₂
C) HCl
D) H⁺
E) Cl⁻
10. In molecular compounds, electrons are:
A) Transferred from metals to nonmetals
B) Transferred from nonmetals to metals
C) Shared between atoms
D) Lost by all atoms
E) Used to form ions
11. Which of these is not typically a property of molecular compounds?
A) Low melting point
B) Poor conductivity
C) Gas or liquid state
D) Composed of ions
E) Covalent bonding
12. In the combustion of glucose (C₆H₁₂O₆), oxygen is:
A) Oxidized
B) Reduced
C) Decomposed
D) Unchanged
E) Neutral
13. Which type of reaction is: 2H₂ + O₂ → 2H₂O?
A) Precipitation
B) Acid-base
C) Redox
D) Decomposition
E) Displacement
14. What is the oxidation state of hydrogen in H₂O?
A) 0
B) –1
C) +2
D) +1
E) –2
15. Why don't most molecular compounds conduct electricity?
A) They are always solids
B) They contain metal atoms
C) They do not contain free ions
D) They are too small
E) They form crystals
16. Which compound is a molecular compound involved in respiration?
A) NaCl
B) O₂
C) CaCO₃
D) MgO
E) KNO₃
17. Which of the following statements about redox and molecular compounds is correct?
A) Molecular compounds never participate in redox reactions
B) Only ionic compounds can be oxidized
C) Molecular compounds can undergo oxidation and reduction
D) Molecular compounds conduct electricity well
E) Redox only applies to metals
18. What happens to the carbon atom in CH₄ during combustion?
A) It is reduced
B) It forms ions
C) It is oxidized to CO₂
D) It remains unchanged
E) It becomes metallic
19. Which of the following is not a redox reaction?
A) Combustion of propane
B) Reaction of H₂ with O₂
C) Formation of water from H₂ and O₂
D) Dissolving sugar in water
E) Oxidation of glucose
20. In molecular compounds, the atoms are usually held together by:
A) Electrostatic attraction
B) Covalent bonds
C) Metallic bonds
D) Hydrogen ions
E) Van der Waals forces only
- Questions on Oxygen in Reactions — Oxidation and Reduction
- Questions on Redox Reactions and Ionic Compounds
Answers with Explanations
1. C – Molecular compounds form through electron sharing between nonmetals (covalent bonds).
2. C – CO₂ is made of two nonmetals → molecular.
3. C – Molecular compounds generally do not conduct electricity in solution.
4. B – Oxidation = loss of electrons.
5. A – Carbon in CH₄ is oxidized to CO₂.
6. C – Oxygen goes from 0 to –2 → reduction (oxidation number decreases).
7. C – Covalent bonds = shared electrons in molecular compounds.
8. A – Water is molecular and involved in many redox reactions.
9. A – H₂ donates electrons, so it is the reducing agent.
10. C – In molecular compounds, atoms share electrons.
11. D – Molecular compounds are not made of ions.
12. B – Oxygen is reduced in respiration (accepts electrons).
13. C – This is a classic redox reaction (oxidation of H₂, reduction of O₂).
14. D – Hydrogen is usually +1 in water.
15. C – No free ions, so molecular compounds usually do not conduct electricity.
16. B – O₂ is a key molecular reactant in respiration.
17. C – Molecular compounds can undergo oxidation/reduction.
18. C – Carbon is oxidized to CO₂ during combustion.
19. D – Dissolving sugar is physical, not a redox reaction.
20. B – Covalent bonds hold molecular compounds together.
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