Free Redox Reactions MCQs with Answers

• A. the sulphate ion
• B. copper ions
• C. zinc
• D. copper metal

Explanation: Zinc goes from an oxidation number of zero as the metal to plus 2 in the sulphate, so it has lost electrons and is oxidised, which also…

• A. a neutralisation reaction
• B. a displacement reaction
• C. a precipitation reaction
• D. a disproportionation reaction

Explanation: In disproportionation one species with an intermediate oxidation state changes into two products, one at a higher and one at a lower…

• A. cathode
• B. salt bridge
• C. anode
• D. voltmeter

Explanation: The anode is by definition the electrode at which oxidation occurs and reduction occurs at the cathode, and this holds for both galvanic…

• A. allow electrons to pass between the two solutions
• B. complete the circuit by allowing ions to migrate and keeping both solutions electrically neutral
• C. prevent the cell from producing any current
• D. act as a catalyst for the reaction

Explanation: As the cell runs, positive charge builds up in one half cell and negative charge in the other, which would stop the reaction almost…

• A. lose electrons there
• B. gain electrons and are reduced there
• C. are attracted to the anode
• D. react with chlorine there

Explanation: Positive sodium ions migrate to the negative cathode, each accepting one electron to become a sodium atom, which is reduction.

• A. Zn + 2HCl gives ZnCl2 + H2
• B. 2H2 + O2 gives 2H2O
• C. NaOH + HCl gives NaCl + H2O
• D. 2Mg + O2 gives 2MgO

Explanation: In neutralisation no element changes its oxidation number, since hydrogen stays at plus 1, oxygen at minus 2 and both sodium and chlorine…

• A. displace a metal lower in the series from its salt solution
• B. be displaced by a metal lower in the series
• C. never react with acids
• D. always be a poor conductor

Explanation: A more reactive metal gives up electrons more readily, so it reduces the ions of a less reactive metal and takes their place in solution…

• A. Water boiling to steam
• B. Hydrogen gas reacting with chlorine to form hydrogen chloride gas
• C. Sodium chloride dissolving in water
• D. Ethanol evaporating at room temperature

Explanation: Hydrogen goes from zero to plus 1 and chlorine from zero to minus 1, so electrons are transferred and oxidation numbers change, which is…

• A. CuSO4
• B. AgNO3
• C. K2MnO4
• D. CH3COOH

Explanation: AgNO3 produces black spots on skin and cellulose because light or organic matter reduces Ag+ to finely divided metallic silver, which…

• A. NaHSO3
• B. Na2S2O3
• C. Na2S
• D. Na2SO3

Explanation: Sodium thiosulfate, Na2S2O3, is used as photographic fixer because it dissolves unexposed silver halide by forming a soluble…

• A. Free radicals
• B. Cosmic rays
• C. Nitrogen oxides
• D. UV -rays

Explanation: Ultraviolet rays split O2 molecules into oxygen atoms, and these atoms then combine with O2 to form O3 in the upper atmosphere.

• A. +ve
• B. -ve
• C. Neutral
• D. None

Explanation: A cation forms when an atom or group loses one or more electrons, leaving more protons than electrons and giving a positive charge.

• A. Zinc
• B. Carbon (Graphite)
• C. ZnCl²
• D. MnO²(Pyrolusite)

Explanation: In a zinc-carbon dry cell, the graphite rod serves as the cathode and conducts electrons from the manganese dioxide cathodic mixture.

• A. Electrolytic cell
• B. Galvanic cell
• C. Daniel cell
• D. Not

Explanation: An electrolytic cell requires an external electrical source to drive a non-spontaneous redox reaction, so its cell reaction does not…

• A. Nitrification
• B. Fermentation
• C. Denitrification
• D. None of these

Explanation: Nitrification is the bacterial oxidation of ammonia or ammonium compounds first to nitrite and then to nitrate, NO3−.

• A. K2Cr2O7
• B. H2SO4
• C. SO3
• D. P2O5

Explanation: SO2 is a reducing agent and reduces orange dichromate ions, Cr2O7^2-, to green Cr3+ ions in acidic solution.

• A. 4.8
• B. 5.2
• C. 8.8
• D. 8.4

Explanation: For hydrogen peroxide decomposition, 1 equivalent of H2O2 produces 5.6 L of O2 at STP per litre of a 1 N solution.

• A. 10 grams of H2O2 solution liberate 10 mL of O2 at STO
• B. 10 gram equivalents of H2O2 liberates 10 mL of O2 at STP
• C. 10 litres of H2O2 liberates 19 mL of O2 at STP
• D. 1mL of solution of H2O2 liberates 10 mL of O2 at STP

Explanation: A 10-volume H2O2 solution liberates 10 mL of oxygen gas at STP from every 1 mL of the solution.

• A. C
• B. Zn
• C. Al
• D. Cu

Explanation: Carbon acts as a reducing agent during smelting because it removes oxygen from metal oxides, producing the metal and carbon monoxide or…

• A. Reduce it
• B. Oxidize it
• C. Obtain an alloy
• D. Separate volatile impurities

Explanation: Smelting uses heat and a reducing agent to convert a concentrated metal oxide into the free metal, so its main purpose is reduction.