Concepts of oxidation and reduction MCQs With Answer

Concepts of oxidation and reduction MCQs With Answer introduce essential redox principles crucial for B. Pharm students studying pharmaceutical chemistry, drug metabolism, and analytical methods. This concise guide covers electron transfer, oxidation states, oxidizing and reducing agents, half-reactions, redox titrations, electrode potentials, and biological redox systems like cytochrome P450 and NAD+/NADH. Emphasis is placed on practical examples relevant to drug synthesis, stability, and metabolism, plus techniques for balancing redox equations and interpreting electrochemical data. Clear explanations help build problem-solving skills needed in pharm courses and laboratory practice. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the formal definition of oxidation in redox chemistry?

• Loss of electrons
• Gain of electrons
• Gain of protons
• Increase in mass

Correct Answer: Loss of electrons

Q2. What is the oxidation state of sulfur in H2SO4?

• +2
• +4
• +6
• -2

Correct Answer: +6

Q3. Which description best defines a reducing agent?

• Species that accepts electrons and is reduced
• Species that donates electrons and is oxidized
• Species that increases pH
• Species that catalyzes a reaction without changing

Correct Answer: Species that donates electrons and is oxidized

Q4. In the half-reaction Fe2+ -> Fe3+ + e-, Fe2+ acts as:

• An oxidizing agent
• A reducing agent
• An inert spectator
• An acid

Correct Answer: A reducing agent

Q5. What is disproportionation (disproportionation reaction)?

• One element is both oxidized and reduced in the same reaction
• Two species exchange protons
• A reaction where only electrons are transferred without change in oxidation state
• Hydrolysis of an ester

Correct Answer: One element is both oxidized and reduced in the same reaction

Q6. In the reaction Zn + Cu2+ -> Zn2+ + Cu, which is the oxidizing agent?

• Zn
• Cu2+
• Zn2+
• Cu

Correct Answer: Cu2+

Q7. The biochemical reduction NAD+ + H+ + 2 e- -> NADH involves how many electrons?

• 1 electron
• 2 electrons
• 3 electrons
• 0 electrons

Correct Answer: 2 electrons

Q8. What is the oxidation state of carbon in methanol, CH3OH?

• 0
• -1
• -2
• +2

Correct Answer: -2

Q9. A more positive standard reduction potential (E°) indicates:

• Greater tendency to be oxidized
• Greater tendency to be reduced
• No tendency to undergo redox
• Only acid–base reactivity

Correct Answer: Greater tendency to be reduced

Q10. The Nernst equation is used to:

• Calculate equilibrium constant from ΔH only
• Calculate cell potential under non-standard conditions
• Determine molecular weight of a compound
• Convert mass to moles

Correct Answer: Calculate cell potential under non-standard conditions

Q11. In acidic solution, permanganate ion (MnO4-) is commonly reduced to which species?

• MnO2
• Mn2+
• Mn3+
• MnO4^2-

Correct Answer: Mn2+

Q12. Which oxidizing reagent also acts as its own indicator in titrations (self-indicator)?

• Potassium permanganate (KMnO4)
• Phenolphthalein
• Bromothymol blue
• Starch

Correct Answer: Potassium permanganate (KMnO4)

Q13. In drug metabolism, cytochrome P450 enzymes primarily catalyze which type of redox transformation?

• Reduction of carboxylic acids to alcohols
• Oxidation of drugs by insertion of oxygen (Phase I reactions)
• Formation of disulfide bonds
• Hydrolysis without redox change

Correct Answer: Oxidation of drugs by insertion of oxygen (Phase I reactions)

Q14. In the decomposition 2 H2O2 -> 2 H2O + O2, which change occurs to oxygen in H2O2?

• All oxygen atoms are reduced
• All oxygen atoms are oxidized
• Some oxygen is reduced and some is oxidized
• Oxygen remains at the same oxidation state

Correct Answer: Some oxygen is reduced and some is oxidized

Q15. For the reaction 2 Fe2+ + Cl2 -> 2 Fe3+ + 2 Cl-, the oxidizing agent is:

• Fe2+
• Fe3+
• Cl2
• Cl-

Correct Answer: Cl2

Q16. Which process corresponds to an increase in oxidation number of an atom?

• Reduction
• Oxidation
• Protonation
• Hydrolysis

Correct Answer: Oxidation

Q17. When balancing redox reactions in acidic solution by the half-reaction method, which species are added to balance oxygen and hydrogen?

• O2 and H2
• H2O and H+
• OH- and H2O
• Electrons only

Correct Answer: H2O and H+

Q18. In biological oxidation of ethanol to acetaldehyde, which coenzyme commonly acts as the oxidizing agent?

• FADH2
• NAD+
• ATP
• CoA-SH

Correct Answer: NAD+

Q19. Which of the following is the strongest reducing agent?

• LiAlH4
• H2O2
• KMnO4
• O2

Correct Answer: LiAlH4

Q20. In an electrochemical (galvanic) cell, the direction of electron flow is from:

• Cathode to anode
• Anode to cathode
• Salt bridge to anode
• Internal solution to external circuit

Correct Answer: Anode to cathode

Q21. What is the oxidation number of nitrogen in the ammonium ion NH4+?

• +1
• -1
• -3
• +3

Correct Answer: -3

Q22. Which reaction is an example of disproportionation?

• 2 H2 + O2 -> 2 H2O
• 2 H2O2 -> 2 H2O + O2
• CH4 + Cl2 -> CH3Cl + HCl
• Cu + 2 Ag+ -> Cu2+ + 2 Ag

Correct Answer: 2 H2O2 -> 2 H2O + O2

Q23. In the redox reaction Cu + 2 Ag+ -> Cu2+ + 2 Ag, which species is the oxidizing agent?

• Cu
• Ag+
• Cu2+
• Ag

Correct Answer: Ag+

Q24. The standard cell potential E°cell is calculated as:

• E°cell = E°anode – E°cathode
• E°cell = E°cathode – E°anode
• E°cell = E°cathode + E°anode
• E°cell = E°anode / E°cathode

Correct Answer: E°cell = E°cathode – E°anode

Q25. Which indicator is commonly used to detect the endpoint in iodometric titrations (forms a blue complex with iodine)?

• Phenolphthalein
• Starch
• Methyl orange
• Bromothymol blue

Correct Answer: Starch

Q26. Oxidation of a primary alcohol typically yields which product after complete oxidation?

• A primary amine
• An aldehyde followed by carboxylic acid on further oxidation
• A ketone directly
• An ether

Correct Answer: An aldehyde followed by carboxylic acid on further oxidation

Q27. What is the oxidation state of chromium in K2Cr2O7?

• +2
• +3
• +6
• +7

Correct Answer: +6

Q28. Which compound can act both as an oxidizing and reducing agent?

• O2
• H2O2
• Cl2
• NaCl

Correct Answer: H2O2

Q29. In a galvanic cell, which statement is true about the anode?

• Anode is positive and reduction occurs there
• Anode is negative and oxidation occurs there
• Anode is neutral and no reaction occurs
• Anode is where electrons are consumed

Correct Answer: Anode is negative and oxidation occurs there

Q30. Which is the correct form of the Nernst equation at 25°C for a redox reaction?

• E = E° + (0.0592/n) log Q
• E = E° – (0.0592/n) log Q
• E = E° – (0.0257/n) ln Q
• E = E° + (0.0257/n) ln Q

Correct Answer: E = E° – (0.0592/n) log Q

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com