Free Redox Reactions MCQs with Answers
102 Redox Reactions MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Redox reactions involve oxidation and reduction occurring together, with electrons transferred between species or oxidation numbers changing. The topic covers assigning oxidation states, identifying oxidizing and reducing agents, balancing redox equations by oxidation number or half-reaction methods, and connecting chemical changes with galvanic and electrolytic cells.
Last updated
102 questions · page 2 of 6
- A. 2
- B. 3
- C. 4
- D. 5
Explanation: Nitric acid is a strong acid, so a 0.001 mol L^-1 HNO3 solution dissociates almost completely and gives [H+] = 0.001 mol L^-1 = 10^-3 mol…
Correct answer: 3- A. It is a sterilising agent.
- B. It dissolves the impurities of water.
- C. It is a reducing agent.
- D. It is an oxidising agent.
Explanation: Potassium permanganate, KMnO4, oxidises many dissolved organic and microbial impurities, so it helps purify water by acting as an…
Correct answer: It is an oxidising agent.- A. Sulphur dioxide
- B. Sulphuryl chloride
- C. Suphanyl chloride
- D. All of the above
Explanation: The intended reactant is chlorine, Cl2, and SO2 reacts with it in sunlight to form sulfuryl chloride, SO2Cl2.
Correct answer: Sulphuryl chloride- A. H2S2O3
- B. H2SO8
- C. H2S4O6
- D. H2 S2 O6
Explanation: H2SO8 contains a peroxide O-O linkage, represented in its structure as a peroxodisulfuric acid unit.
Correct answer: H2SO8- A. N2O3
- B. NO2
- C. NO
- D. N2O
Explanation: The nitrate ion is reduced to NO, which combines with Fe2+ in acidic solution to form the brown nitrosyl complex, commonly represented as…
Correct answer: NO- A. FeSO4.No
- B. FeSO4.No2
- C. FeSO4.No3
- D. FeSO4.N2o
Explanation: In the brown-ring test, NO formed from nitrate coordinates with Fe2+ to produce a nitrosyl complex, conventionally written in simplified…
Correct answer: FeSO4.No- A. Oxidation
- B. Reduction
- C. Decomposition
- D. Both b & c
Explanation: H3PO3 undergoes disproportionation on heating: some phosphorus(III) is oxidised to phosphorus(V) in H3PO4, while some is reduced to…
Correct answer: Both b & c- A. activation
- B. enameling
- C. corrosion
- D. coating
Explanation: Corrosion is the gradual chemical or electrochemical deterioration of a metal through reaction with oxygen, moisture, acids or other…
Correct answer: corrosion- A. dry cell
- B. galvanic cell
- C. electrolytic cell
- D. A and B
Explanation: When aluminium and copper are connected in the presence of an electrolyte, aluminium is oxidised and copper acts as the site of reduction…
Correct answer: galvanic cell- A. corrode slowly
- B. corrode rapidly
- C. does not corrode easily
- D. none of these
Explanation: A pure metal generally resists corrosion more readily than an impure metal because local galvanic cells are less likely to form between…
Correct answer: does not corrode easily- A. MnO2
- B. Zn
- C. AgO2
- D. cadmium
Explanation: In an alkaline battery, zinc is oxidized at the anode: Zn -> Zn2+ + 2e-.
Correct answer: Zn- A. 1.25g/cm3
- B. 1.3g/cm3
- C. 1.20g/cm3
- D. 1.15g/cm3
Explanation: The sulfuric acid electrolyte of a lead-acid accumulator has a density of about 1.25 g/cm3 under the commonly quoted operating condition.
Correct answer: 1.25g/cm3- A. rechargeable
- B. non rechargeable
- C. electrolytic cell
- D. Daniel cell
Explanation: A secondary cell can be recharged because its electrode reactions are reversible, allowing electrical energy to restore the original…
Correct answer: rechargeable- A. electrons
- B. anion
- C. current
- D. ions
Explanation: A salt bridge contains an inert electrolyte whose cations and anions migrate to maintain electrical neutrality in the two half-cells, so…
Correct answer: ions- A. free electrons
- B. ions
- C. metals
- D. electrodes
Explanation: In an electrolytic solution, dissolved ions move toward oppositely charged electrodes and carry charge through the solution.
Correct answer: ions- A. Pressure increases
- B. Dilution decreases
- C. Dilution increases
- D. None
Explanation: Dilution increases the degree of dissociation of a weak electrolyte because the lower concentration reduces the tendency of oppositely…
Correct answer: Dilution increases- A. The flow of electrons takes place from copper to zinc
- B. E0red of copper electrode is less than that of zinc electrode
- C. Zinc acts as an anode and copper as cathode
- D. All are correct
Explanation: In a Zn-Cu galvanic cell, zinc is oxidised at the anode and copper ions are reduced at the cathode, so zinc is the anode and copper is the…
Correct answer: Zinc acts as an anode and copper as cathode- A. wire
- B. salt bridge
- C. electric circuit
- D. no connection exists
Explanation: The two half-cells are connected internally by a salt bridge, which permits ion migration and maintains electrical neutrality.
Correct answer: salt bridge- A. 40%
- B. 25%
- C. 30%
- D. 50%
Explanation: The electrolyte of a charged lead accumulator is aqueous sulfuric acid with a concentration commonly taken as about 30% by mass in basic…
Correct answer: 30%- A. 1.5 volts
- B. 2 volts
- C. 3 volts
- D. 1 volts
Explanation: A single lead-acumulator cell produces about 2 volts because the lead dioxide and lead electrode reactions have a potential difference of…
Correct answer: 2 volts