Class 11 – Redox Reactions (40 MCQs)
Basic Concepts (1–6)
- Oxidation is defined as:
a) Loss of electrons
b) Gain of electrons
c) Loss of protons
d) Gain of protons - Reduction is:
a) Loss of electrons
b) Gain of electrons
c) Loss of oxygen
d) Gain of hydrogen - In the reaction Zn + Cu²⁺ → Zn²⁺ + Cu, the oxidizing agent is:
a) Zn
b) Cu²⁺
c) Zn²⁺
d) Cu - In the same reaction, the reducing agent is:
a) Zn
b) Cu²⁺
c) Zn²⁺
d) Cu - Redox reactions involve:
a) Only oxidation
b) Only reduction
c) Both oxidation and reduction
d) Only acid-base reactions - In H₂O₂ → H₂O + O₂, H₂O₂ acts as:
a) Oxidizing agent only
b) Reducing agent only
c) Both oxidizing and reducing agent
d) Neither
Oxidation Numbers & Rules (7–13)
- Oxidation number of O in H₂O₂ is:
a) –2
b) –1
c) 0
d) +1 - Oxidation number of Cl in Cl₂ is:
a) 0
b) –1
c) +1
d) +2 - Oxidation number of N in NH₄⁺ is:
a) –3
b) +1
c) +3
d) 0 - Oxidation number of S in SO₄²⁻ is:
a) +4
b) +6
c) –2
d) 0 - Oxidation number of Mn in KMnO₄ is:
a) +6
b) +7
c) +2
d) +4 - Oxidation number of Fe in Fe₂O₃ is:
a) +2
b) +3
c) +6
d) +0 - Oxidation number of C in CO₂ is:
a) +2
b) +4
c) –2
d) 0
Balancing Redox Reactions (14–22)
- In acidic medium, H⁺ ions are used to:
a) Balance oxygen
b) Balance hydrogen
c) Balance electrons
d) Balance charge - In basic medium, OH⁻ ions are used to:
a) Balance oxygen
b) Balance hydrogen
c) Balance electrons
d) Balance charge - Half-reaction method involves:
a) Dividing reaction into oxidation and reduction halves
b) Using only H⁺ ions
c) Ignoring electrons
d) None - The reaction Fe²⁺ → Fe³⁺ involves:
a) Oxidation
b) Reduction
c) Both
d) Neither - In Cr₂O₇²⁻ + Fe²⁺ → Cr³⁺ + Fe³⁺ in acidic medium, the oxidizing agent is:
a) Fe²⁺
b) Cr₂O₇²⁻
c) Fe³⁺
d) Cr³⁺ - In the above reaction, the reducing agent is:
a) Fe²⁺
b) Cr₂O₇²⁻
c) Fe³⁺
d) Cr³⁺ - In redox reactions, total electrons lost =
a) Total electrons gained
b) Always greater
c) Always smaller
d) Not related - In basic medium, after balancing half-reactions using H⁺, what is the next step?
a) Add OH⁻ equal to H⁺
b) Ignore H⁺
c) Add electrons
d) Add water only - For MnO₄⁻ → Mn²⁺ in acidic medium, number of electrons transferred =
a) 3
b) 5
c) 1
d) 2
Redox Reactions in Acidic & Basic Medium (23–27)
- HNO₃ acts as an oxidizing agent in:
a) Acidic medium
b) Basic medium
c) Both
d) Neither - H₂O₂ acts as a reducing agent in:
a) Acidic medium
b) Basic medium
c) Both
d) Neither - Cl₂ in water can act as:
a) Oxidizing agent
b) Reducing agent
c) Both
d) Neither - In basic medium, Fe³⁺ → Fe²⁺ requires:
a) H⁺ ions
b) OH⁻ ions
c) Electrons
d) Water - In acidic solution, Cr₂O₇²⁻ → Cr³⁺ requires:
a) H⁺ and electrons
b) OH⁻ only
c) Electrons only
d) No ions
Electrochemical Aspects (28–31)
- Oxidation occurs at:
a) Cathode
b) Anode
c) Electrolyte
d) Both electrodes - Reduction occurs at:
a) Cathode
b) Anode
c) Electrolyte
d) None - In Zn/Cu electrochemical cell, electrons flow from:
a) Cu to Zn
b) Zn to Cu
c) Cu to electrolyte
d) Zn to electrolyte - Standard electrode potential indicates:
a) Tendency to oxidize or reduce
b) Solubility
c) Temperature
d) Pressure
Applications & Conceptual Questions (32–40)
- Bleaching powder is used as:
a) Oxidizing agent
b) Reducing agent
c) Both
d) Neither - Rusting of iron is:
a) Oxidation only
b) Reduction only
c) Redox reaction
d) Acid-base reaction - Oxidation number of S in H₂SO₃ is:
a) +4
b) +6
c) –2
d) 0 - Oxidation number of Cl in ClO⁻ is:
a) +1
b) +3
c) –1
d) 0 - In redox titrations, KMnO₄ acts as:
a) Oxidizing agent
b) Reducing agent
c) Both
d) None - In redox titration, Na₂S₂O₃ is used as:
a) Oxidizing agent
b) Reducing agent
c) Both
d) None - Disproportionation reaction is:
a) One species oxidized
b) One species reduced
c) Same species both oxidized and reduced
d) Two different species react - HClO₄ acts as:
a) Oxidizing agent
b) Reducing agent
c) Both
d) Neither - Oxidation number of Mn in MnO₂ is:
a) +2
b) +4
c) +6
d) +7
Answer Key – Class 11 Chemistry: Redox Reactions (40 MCQs)
Basic Concepts (1–6)
- a) Loss of electrons – Oxidation is the loss of electrons.
- b) Gain of electrons – Reduction is the gain of electrons.
- b) Cu²⁺ – Cu²⁺ gains electrons → oxidizing agent.
- a) Zn – Zn loses electrons → reducing agent.
- c) Both oxidation and reduction – Redox reactions involve simultaneous oxidation and reduction.
- c) Both oxidizing and reducing agent – H₂O₂ can gain or lose electrons.
Oxidation Numbers & Rules (7–13)
- b) –1 – Oxygen in H₂O₂ has –1.
- a) 0 – Cl in elemental Cl₂ is 0.
- a) –3 – NH₄⁺: N = –3, H = +1 each.
- b) +6 – SO₄²⁻: S = +6.
- b) +7 – KMnO₄: Mn = +7.
- b) +3 – Fe₂O₃: Fe = +3.
- b) +4 – CO₂: C = +4.
Balancing Redox Reactions (14–22)
- b) Balance hydrogen – H⁺ used to balance H in acidic medium.
- b) Balance hydrogen – OH⁻ used to balance H in basic medium.
- a) Dividing reaction into oxidation and reduction halves – Half-reaction method.
- a) Oxidation – Fe²⁺ → Fe³⁺ loses 1 electron.
- b) Cr₂O₇²⁻ – Cr₂O₇²⁻ gets reduced → oxidizing agent.
- a) Fe²⁺ – Fe²⁺ gets oxidized → reducing agent.
- a) Total electrons lost = Total electrons gained – Electron conservation in redox.
- a) Add OH⁻ equal to H⁺ – Convert acidic half-reaction to basic medium.
- b) 5 – MnO₄⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H₂O
Redox Reactions in Acidic & Basic Medium (23–27)
- a) Acidic medium – HNO₃ is strong oxidizing agent in acid.
- c) Both – H₂O₂ can act as oxidizing or reducing agent depending on medium.
- c) Both – Cl₂ can oxidize or reduce.
- c) Electrons – Fe³⁺ → Fe²⁺ requires electron transfer.
- a) H⁺ and electrons – Acidic medium requires H⁺ and electron balance.
Electrochemical Aspects (28–31)
- b) Anode – Oxidation occurs at anode.
- a) Cathode – Reduction occurs at cathode.
- b) Zn to Cu – Electrons flow from Zn (anode) to Cu (cathode).
- a) Tendency to oxidize or reduce – Standard electrode potential indicates reactivity.
Applications & Conceptual Questions (32–40)
- a) Oxidizing agent – Bleaching powder oxidizes stains.
- c) Redox reaction – Rusting involves Fe oxidation and O₂ reduction.
- a) +4 – H₂SO₃: S = +4.
- a) +1 – ClO⁻: Cl = +1.
- a) Oxidizing agent – KMnO₄ oxidizes Fe²⁺, oxalate, etc.
- b) Reducing agent – Na₂S₂O₃ reduces iodine in titrations.
- c) Same species both oxidized and reduced – Definition of disproportionation.
- a) Oxidizing agent – HClO₄ is strong acid + oxidizer.
- b) +4 – Mn in MnO₂ = +4.
Disclaimer:
All MCQs on this page are created for educational purposes only. They are intended for practice and NEET/Class 11 Chemistry preparation and do not guarantee any specific exam results.