Redox ReactionsNEET MCQs with solutions
Redox Reactions covers oxidation-reduction concepts, oxidation numbers, balancing redox equations (half-reaction and oxidation number methods), and electrochemical cells. NEET tests oxidation state assignment, identifying oxidising/reducing agents, and balancing redox reactions — mostly conceptual, fast-scoring questions.
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- 11 Chemistry
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Tap an option to check it. Questions from every NCERT topic in this chapter, from easy to hard.
Q1Important PYQ Mixed Concepts
For the equilibrium 2A(g) ⇌ B(g) + C(g), Kc = 4 × 10⁻³. At a particular instant [A] = [B] = [C] = 2 × 10⁻³ M. What is the direction of spontaneous shift?
Not quite — the answer is B.
Qc = [B][C]/[A]² = (2×10⁻³)²/(2×10⁻³)² = 1. Since Qc (1) > Kc (4×10⁻³), the reaction shifts in the backward direction. Forward shift occurs only when Qc < Kc. No shift applies only when Qc = Kc. Complete conversion is not possible for a reversible equilibrium.
Q2Important PYQ Mixed Concepts
In the reaction xCl2 + 6OH− → ClO3− + yCl− + 3H2O, the values of x and y are:
Not quite — the answer is B.
Balance chlorine atoms: 2x = 1 + y. Balancing charge: −6 = −1 − y, so y = 5 and x = 3. The correct pair is x = 3, y = 5.
Q3Mixed Revision
Consider the compounds KO2, H2O2 and H2SO4. The oxidation states of oxygen, oxygen and sulfur respectively are:
Not quite — the answer is A.
In KO2, oxygen has an average oxidation state of −1/2 because it is a superoxide. In H2O2, oxygen is −1 because of the peroxide linkage. In H2SO4, sulfur is +6. Option C is wrong because H2SO4 sulfur is +6 not +4, and H2O2 oxygen is −1 not −2. Option B wrongly assigns −2 to H2O2. Option D reverses the KO2 and H2O2 values.
Q4Mixed Revision
Which reaction is NOT a redox reaction?
Not quite — the answer is A.
In BaCl2 + Na2SO4 → BaSO4 + 2NaCl, no element changes its oxidation state. It is a double-displacement precipitation reaction, not a redox reaction. In Options B, C and D, elements clearly change oxidation states, making them redox reactions.
Q5Grand Test
When a zinc rod is placed directly into CuSO4 solution, which observation is correct?
Not quite — the answer is D.
Zinc is oxidised to Zn2+, while Cu2+ is reduced to Cu. Therefore Cu2+ concentration decreases and the blue colour of the solution becomes less intense. Copper deposits on the zinc rod while zinc dissolves; hence the rod does not simply increase in weight. Option C is incorrect because a temperature fall is not a necessary consequence.
Q6Grand Test
Why can HNO2 act as both an oxidising and a reducing agent?
Not quite — the answer is B.
Nitrogen in HNO2 is at +3, which is an intermediate oxidation state for nitrogen. It can be oxidised to higher states such as +5 or reduced to lower oxidation states such as 0 or −3. Therefore HNO2 can show both reducing and oxidising behaviour depending on the reaction. A maximum or minimum oxidation state would restrict movement to only one direction.
Q7Types of Redox Reactions
Which of the following represents a combination redox reaction?
Not quite — the answer is A.
In 2Mg+O₂→2MgO, two substances combine into one product while Mg is oxidised (0 to +2) and O is reduced (0 to −2). Option D is disproportionation, not combination. Options B and C are decomposition and displacement respectively.
Q8Types of Redox Reactions
Decomposition of KClO₃ to KCl and O₂ is a redox reaction because:
Not quite — the answer is B.
Cl is reduced from +5 to −1 (in KCl) while O is oxidised from −2 to 0 (in O₂), making this a redox decomposition. Both half-processes occur simultaneously.
Q9Balancing of Redox Reactions
Which method uses change in oxidation number to balance redox reactions?
Not quite — the answer is A.
The oxidation number method equates total increase in oxidation number with total decrease, then uses this ratio as coefficients. The ion-electron (half-reaction) method instead splits the equation and balances electrons in each half separately.
Q10Balancing of Redox Reactions
In the ion-electron method for acidic medium, which species is added to balance oxygen atoms?
Not quite — the answer is B.
Oxygen atoms are balanced by adding H₂O to the side deficient in oxygen. H⁺ is then added to the other side to balance the hydrogen introduced. OH⁻ is used only in basic medium.
Q11Oxidation Number
What is the oxidation number of oxygen in most of its compounds?
Not quite — the answer is A.
Oxygen is assigned −2 in most compounds. The key exceptions are peroxides (−1), superoxides (−½), and OF₂ (+2). Option B (−1) is the trap — it applies only to peroxides, not the general rule.
Q12Oxidation Number
What is the oxidation number of hydrogen in H₂O?
Not quite — the answer is A.
In covalent compounds with non-metals, hydrogen is +1. The −1 value applies only to metal hydrides (NaH, CaH₂) where the metal is less electronegative than hydrogen — a frequent NEET trap.
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Get RankUp on Google PlayQ13Concept of Oxidation and Reduction
Which statement correctly defines oxidation in terms of electron transfer?
Not quite — the answer is A.
Oxidation is defined as loss of electrons (modern electronic concept). Gain of electrons is reduction. Proton transfer defines acid-base reactions, not redox.
Q14Concept of Oxidation and Reduction
Reduction in the modern electronic concept involves:
Not quite — the answer is C.
Reduction is gain of electrons (OIL RIG: Reduction Is Gain). Loss of electrons is oxidation; proton transfer belongs to acid-base chemistry, not redox.
Q15Redox Reactions in Terms of Electrode Processes
Which of the following correctly pairs each electrode with the process occurring at it?
Not quite — the answer is A.
Oxidation (electron loss) always occurs at the anode and reduction (electron gain) always occurs at the cathode — this holds in both galvanic and electrolytic cells. The terms anode and cathode are defined by the process, not by the sign of the electrode.
Q16Redox Reactions in Terms of Electrode Processes
In the external circuit of a galvanic cell, electrons flow from:
Not quite — the answer is C.
Electrons are released at the anode (oxidation) and travel through the external circuit to the cathode (reduction). Conventional current flows opposite to electron flow — from cathode to anode externally — making option B a common trap.
Q17Applications of Redox Reactions
Which of the following correctly describes the chemical nature of corrosion?
Not quite — the answer is A.
Corrosion is an electrochemical process in which metals lose electrons (oxidation) in the presence of moisture and oxygen; the metal acts as anode and the oxide/hydroxide layer forms at the cathode site. It is not a physical process and does not involve reduction of the metal.
Q18Applications of Redox Reactions
Which of the following correctly identifies the oxidising and reducing agents in the rusting of iron?
Not quite — the answer is C.
Iron (Fe → Fe²⁺/Fe³⁺) loses electrons and is oxidised — it is the reducing agent. Oxygen (O₂ → O²⁻) gains electrons and is reduced — it is the oxidising agent. Option B is the trap: water acts as the electrolytic medium, not the oxidising agent.
Q19Concept of Oxidation and Reduction
In the reaction CuO + H₂ → Cu + H₂O, which species is oxidised and which is reduced?
Not quite — the answer is B.
H₂ loses hydrogen (classical) and electrons (modern) → oxidised; CuO loses oxygen and Cu²⁺ gains electrons → reduced. The tempting error is reversing the roles since H₂ appears to "combine" with oxygen.
Q20Concept of Oxidation and Reduction
Which species acts as the reducing agent in Zn + Cu²⁺ → Zn²⁺ + Cu?
Not quite — the answer is D.
Zn loses electrons (is oxidised) and thereby reduces Cu²⁺ → Zn is the reducing agent. Cu²⁺ gains electrons → it is the oxidising agent, a common confusion.
Q21Concept of Oxidation and Reduction
According to the classical concept, oxidation is defined as:
Not quite — the answer is A.
Classically, oxidation = addition of oxygen OR removal of hydrogen. Option B describes classical reduction. Options C and D belong to the modern electronic concept.
Q22Concept of Oxidation and Reduction
Which of the following correctly represents reduction according to the classical oxygen concept?
Not quite — the answer is B.
Classical reduction (oxygen concept) = removal of oxygen. Gain of hydrogen is reduction by the hydrogen concept. Gain/loss of electrons is the modern concept.
Q23Concept of Oxidation and Reduction
In Fe₂O₃ + 3CO → 2Fe + 3CO₂, the role of CO is:
Not quite — the answer is A.
CO loses oxygen from Fe₂O₃ and itself gains oxygen (CO→CO₂) → CO is oxidised and acts as reducing agent. The trap is thinking CO "removes" oxygen so it must be the oxidising agent.
Q24Concept of Oxidation and Reduction
Which of the following statements about oxidation is INCORRECT?
Not quite — the answer is D.
Oxidation never necessarily involves gain of protons — that is an acid-base process. Options A, B, C are all valid definitions/consequences of oxidation.
ELITE question · AIR under 50 level
This chapter has 184 ELITE questions for students aiming at the very top. They are only in the app.
Unlock ELITE questions in the appKey Redox Concepts
Quick revision: most questions in this chapter test these facts.
| Concept | Key Fact |
|---|---|
| Oxidation | Loss of electrons; increase in oxidation number |
| Reduction | Gain of electrons; decrease in oxidation number |
| Oxidising agent | Gets reduced itself; gains electrons (e.g. KMnO₄, K₂Cr₂O₇) |
| Reducing agent | Gets oxidised itself; loses electrons (e.g. Na, H₂, C) |
| Disproportionation | Same element is both oxidised and reduced (e.g. Cl₂ in NaOH → NaCl + NaClO) |
| Oxidation number rules | Free element = 0; H = +1 (except metal hydrides = −1); O = −2 (except peroxides = −1) |
What the app covers in this chapter
423 questions in total, each with a detailed explanation.
| Important PYQ Mixed Concepts | 101 |
| Mixed Revision | 61 |
| Grand Test | 60 |
| Types of Redox Reactions | 41 |
| Balancing of Redox Reactions | 41 |
| Oxidation Number | 40 |
| Concept of Oxidation and Reduction | 39 |
| Redox Reactions in Terms of Electrode Processes | 20 |
| Applications of Redox Reactions | 20 |
Questions students ask
Is Redox Reactions important for NEET?
Yes — oxidation number assignment and identifying oxidising/reducing agents are tested regularly. It is also essential for understanding electrochemistry in Class 12.
Which topics should I revise first?
Master oxidation number rules and exceptions, identifying oxidising and reducing agents, disproportionation reactions, and balancing redox equations by the half-reaction method.
How many questions from this chapter are on RankUp?
The RankUp app has 423 questions on Redox Reactions, including 184 ELITE questions. Every question has a detailed explanation.
