Electrochemistry MCQs for MDCAT Practice

Chemistry section, Electrochemistry chapter. Sample questions from past PMC papers.

1. Question 1
   A chemist in a specialty chemical plant is reviewing reactions that involve disproportionation, where the same element is both oxidized and reduced. This process is useful for synthesizing compounds with intermediate oxidation states from a single reactant. The chemist examines four possible industrial reactions. Which of the following reactions is an example of a disproportionation redox reaction?
   • A.2Na2S2O3(aq) + I2(s) → Na2S4O6(aq) + 2NaI(aq)
   • B.2FeCl3(aq) + H2S(s) → 2FeCl2 (aq) + 2HCl(aq) + S(s)
   • C.P4 (s)+ 3NaOH(l) + 3H2O(aq) → 3NaH2PO2(aq) + PH3(g)
   • D.2KMnO4(aq) + 8H2SO4(aq) + 10FeSO4(aq) → K2SO4(aq) + 2MnSO4(aq) + 5Fe2(SO4)3(aq) +8H2O(l)
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2. Question 2
   In Kolbe's electrolysis, which specific event creates the carbon-carbon pi-bond?
   • A.Cathode reduction
   • B.Metal oxidation
   • C.NaOH formation
   • D.Radical coupling
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3. Question 3
   The standard redox potential for the half-cell reaction Fe3+ + e− → Fe2+ is +0.77 V.Which cell would be used to determine this standard value?
   • A.Fe electrode in 1 mol dm−3 Fe3+ against Fe electrode in 1 mol dm−3 Fe2+
   • B.Pt electrode in 1 mol dm−3 Fe3+ against Pt electrode in 1 mol dm−3 Fe2+
   • C.Fe electrode in a solution containing 1 mol dm−3 Fe3+ and 1 mol dm−3 Fe2+ against a standard hydrogen electrode
   • D.Pt electrode in a solution containing 1 mol dm−3 Fe3+ and 1 mol dm−3 Fe2+ against a standard hydrogen electrode
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4. Question 4
   In balancing, it is very important to identify the substance whose:
   • A.Physical state is changed
   • B.Oxidation number is changed
   • C.Enthalpy is changed
   • D.All of these
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5. Question 5
   Electrogravimetry achieves separation and quantification by driving which process at a working electrode via the passage of a controlled electrical current?
   • A.Deposition of the analyte
   • B.Selective oxidation of the solvent
   • C.Solution conductance variation
   • D.Potential shift measurement
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6. Question 6
   This one is liberated at the anode during clectrolysis of brine in diaphragm cellis:
   • A.H2
   • B.Na
   • C.Cl2
   • D.O2
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7. Question 7
   In electrochemical cells, reduction takes place at:
   • A.Anode
   • B.Cathode
   • C.At the surface of the electrolyte
   • D.None of these
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8. Question 8
   Which of the following element same oxidation number in all compounds?
   • A.Oxygen
   • B.Fluorine
   • C.chlorine
   • D.Both (A) & (C)
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