Gobezoch › Textbooks › Chemistry Grade 12

Chemistry Grade 12 Unit 2: ELECTROCHEMISTRY

national exam questions have come from this unit. It runs 79 pages; one careful study pass takes about 8.6 hours, and its difficulty is harder among Chemistry units. Each section below lists the questions set from it, with the year, and opens the page that teaches it.

Read this unit
2.1 Oxidation-Reduction Reactions · read p. 57
Not asked in a national paper yet.
2.1.1 Oxidation · read p. 57
Not asked in a national paper yet.
2.1.2 Reduction · read p. 58
Not asked in a national paper yet.
2.1.3 Balancing Oxidation-Reduction (Redox) Reactions · read p. 59
  • 2013 E.C., Q50 – What is reduction? Reduction is
  • 2012 E.C., Q43 – The reaction MnO4- + C2O4^2- → MnO2 + CO3^2- is not balanced. If the reaction is balanced using basic medium, the coefficient of OH- and H2O will be respectively?
  • 2011 E.C., Q71 – For which of the following half-cells is the reduction potential E independent of the pH of the solution?
  • 2008 E.C., Q45 – Which of the following statement(s) is (are) applicable to a balanced chemical equation of an elementary reaction? I. Order is same as molecularity. II. Order is less than the molecularity. III. Order is greater than the
  • 2007 E.C., Q44 – How many electrons will appear when the following half-reaction is balanced? $\mathrm{S_4O_6^{2-}} \rightarrow \mathrm{S_2O_3^{2-}}$
  • 2005 E.C., Q69 – Consider the following unbalanced redox reaction in acidic solution: MnO + Fe →Mn + Fe 4 − 2+ 2+ 3+ Fe2+ what is the change in oxidation state for both the substances oxidized and reduced, and the coefficients of Mn2+ an
  • 2005 E.C., Q35 – What is the equivalent weight of $\mathrm{HNO_3}$, as an oxidizing agent, in the following balanced reaction? $3\mathrm{Fe^{2+}} + 4\mathrm{H^+} + +\mathrm{NO_3^-} \longrightarrow 3\mathrm{Fe^{3+}} + \mathrm{NO} + 2\mat
2.2 Electrolysis of Aqueous Solutions · read p. 66
Not asked in a national paper yet.
2.2.1 Electrolytic Cells · read p. 69
Not asked in a national paper yet.
2.2.2 Preferential Discharge · read p. 70
  • 2015 E.C., Q69 – Why tin does NOT react with cold water but calcium reacts with cold water quite readily?
  • 2007 E.C., Q19 – The decreasing order of electrochemical characteristics of some metals is given as: Mg > Al > Zn > Cu > Ag. What will (Al(NO )) 3 3 happen if a copper spoon is used to stir a solution of aluminium nitrate ?
2.2.3 Electrolysis of Some Selected Aqueous Solutions · read p. 74
  • 2018 E.C., Q54 – An aqueous solution contains Ag⁺(aq) and Cu²⁺(aq) ions. Electrolysis is carried out using inert platinum electrodes. A constant current of 9.65 A is passed through the solution for 1000 seconds. Which metal will be depos
  • 2018 E.C., Q70 – For the electrolysis of aqueous copper (II) sulfate solution using graphite electrode, what substances are produced at anode and cathode electrode respectively and their ratio?
  • 2018 E.C., Q53 – A chemist compares electrolysis of dilute NaCl solution and concentrated NaCl solution using inert electrodes. The substance produced at anode electrode of dilute NaCl solution and concentrated NaCl solution are _____ an
  • 2017 E.C., Q63 – Which of the following occur during the electrolysis of dilute $\mathrm{H_2SO_4}$?
  • 2014 E.C., Q6 – What is meant by preferential discharge, if a number of ions are present in a solution? It means that the one which requires
  • 2013 E.C., Q56 – In the electrolysis of copper sulphate solution using graphite electrodes, O 2 is liberated at the anode and copper metal is deposited at the cathode. If the electrolysis of CuSO 4 is performed using copper electrode, wh
  • 2012 E.C., Q44 – In which of the following aqueous solution can water be oxidized and O2 forms at the anode and water is reduced and H2 forms at the cathode?
  • 2011 E.C., Q54 – A nickel electrode can undergo oxidation to Ni²⁺ ion as follows: → ∘ → ∘ Ni (s) Ni²⁺ (aq) + 2e⁻ E red= -0.28 V 2H₂O(l) 4H⁺ (aq) +O₂(g) +4e⁻ E red= 1.23 V What will happen during the electrolysis of concentrated aqueous s
  • 2011 E.C., Q30 – Which of the following is the correct reaction taking place at the electrodes during the electrolysis of dilute sodium chloride solution?
  • 2010 E.C., Q47 – During the electrolysis of a concentrated aqueous solution of NaCl, what substance is formed at the cathode?
  • 2009 E.C., Q61 – What product(s) is /are formed during the electrolysis of a concentrated aqueous solution of sodium chloride?
  • 2007 E.C., Q62 – During the electrolysis of an aqueous solution of copper sulphate using platinum electrodes, the reaction takes place at the anode is
  • 2006 E.C., Q70 – Which of the following is NOT a characteristic of the electrolytic cell containing aqueous solution of NaCl used in the manufacture of sodium hydroxide?
  • 2005 E.C., Q72 – What reactions occur at the anode and cathode when an aqueous solution of is electrolyzed? red I. S O + 2e →2SO 2 8 2− − 4 2− O + 4H + 4e →2H O 2 + − 2 2H O + 2e →H + 2OH 2 − 2 − 2.01V II. 1.23V III. -0.83V Na + e →Na +
2.3 Quantitative Aspects of Electrolysis · read p. 81
Not asked in a national paper yet.
2.3.1 Faraday’s First Law of Electrolysis · read p. 81
  • 2009 E.C., Q63 – What mass of magnesium (Mg) is produced in the electrolysis of molten $\mathrm{MgCl_2}$, if a current of $7.50 \times 10^2\,\text{A}$ is passed through the molten salt for 1.00 hour?
  • 2006 E.C., Q50 – The half-reaction for formation of magnesium metal upon electrolysis of molten $\mathrm{MgCl_2}$ is: $\mathrm{Mg^{2+}+2e^- \rightarrow Mg}$ What is the mass of magnesium formed upon passage of a current of $60.0\,\mathrm
  • 2005 E.C., Q41 – In the electroplating of nickel from a solution containing ion, what will be the weight of the metal deposited on the cathode by a current of 8 A flowing for 500 minutes?
2.3.2 Faraday’s Second Law of Electrolysis · read p. 84
  • 2011 E.C., Q70 – A certain current produces 0.50 g of hydrogen gas in 2.0 hrs. What is the amount of copper librated from a solution of copper sulfate by the same current flowing for the same time?
  • 2010 E.C., Q71 – Two electrolytic cells were placed in series, one of $\mathrm{AgNO_3}$ and the other of $\mathrm{CuSO_4}$. If 1.273g Ag is deposited, how much Cu was deposited, how much Cu was deposited at the same time?
2.4 Industrial Application of Electrolysis · read p. 87
  • 2018 E.C., Q56 – Aluminum metal reacts spontaneously with iron (II) ions according to the reaction: Al(s) + Fe²⁺(aq) → Al³⁺(aq) + Fe(s). What is the value of ΔG° for the reaction?
  • 2018 E.C., Q55 – A Galvanic cell constructed from a strip of magnesium metal dipped in a solution of magnesium sulfate and a strip of silver metal immersed in a solution of silver nitrate. Which of the following correctly represents the
  • 2017 E.C., Q36 – A student was given a standard Zn(s)| (aq) half-cell and another half-cell containing copper immersed in CuSO 1.00 M (aq). When the Zn was connected as the anode at 25°C, the cell potential reading on the voltmeter shows
  • 2017 E.C., Q2 – Consider the following galvanic cell: When the Zn strip was connected to metal 'B' at $25^\circ\mathrm{C}$, the voltmeter shows $0.51\,\mathrm{V}$. Which of the following is the standard reduction potential of metal 'B'?
  • 2016 E.C., Q52 – Which of the following is NOT the industrial application of electrochemistry?
  • 2015 E.C., Q10 – The heat change at constant pressure that results when 1 mole of a compound is formed from its elements in their standard states is
  • 2015 E.C., Q71 – Which one of the following explains the determination of the cell potential of Zn-Cu cell using voltmeter?
  • 2013 E.C., Q6 – In the Galvanic cell given in the diagram below Identify the component parts correctly labelled for the letters a, b, c, d and choose the correct one among the following a, b, c, and d , respectively
  • 2013 E.C., Q58 – Given the following electromotive series of selected metals with their standard reduction potentials Which of the following statements is correct about reactivity of the metals?
  • 2012 E.C., Q61 – What is E° for the following balanced reaction? Zn(s) + Pb^2+(aq) → Zn^2+(aq) + Pb(s). Given reduction potentials: Zn^2+/Zn = -0.763 V, Pb^2+/Pb = -0.126 V.
  • 2012 E.C., Q45 – If you want to plate out an iron spoon with silver metal, then which of the following is TRUE?
  • 2011 E.C., Q77 – Which of the following metals cannot be electroplated on to the surface of another metal using an aqueous E∘ E∘ E∘ E∘ electrolyte? (Ni²⁺/Ni) = -0.28 V; (Cu²⁺/Cu) = 0.34 V, (Mg ²⁺/Mg) = -2.37 V; (Ag ⁺/Ag) = 0.80 V
  • 2010 E.C., Q70 – What is the standard cell potential of the oxidation of ammonia, given below?
  • 2009 E.C., Q59 – Consider the reaction: , E0 = 0.78V What is the value of E when [Cu ] 2+ [Fe ] 2+ is equal to 0.040M and is equal to 0.40M?
  • 2009 E.C., Q60 – For the electrochemical cell represented by: The standard reduction potentials for and are +0.34 and -0.76V, respectively, what will be the cell reaction that occurs spontaneously and its cell voltage? Cu + Zn = Cu + Zn
  • 2008 E.C., Q11 – For a voltaic (or galvanic) cell using Ag, (1.0m) and Zn, (1.0m) half cells, which of the following statements is incorrect?
  • 2008 E.C., Q65 – The standard cell potential ( ) for the reaction below is 1.10v. What is the cell potential for this reaction when M and [Zn ] = 2+ 1 Zn (s) (aq) 2+ (aq) 2+ + Cu →Zn + Cu M? (s)
  • 2008 E.C., Q21 – No numerical values are shown.]
  • 2008 E.C., Q66 – Which of the following statements is true?
  • 2007 E.C., Q31 – A solution in an electrolytic cell contains $\mathrm{Cu}^{2+}$ ($E^0 = 0.34\text{V}$), $\mathrm{Ag}^{+}$ ($E^0 = 0.80\text{V}$), and $\mathrm{Zn}^{2+}$ ($E^0 = 0.76\text{V}$). If the voltage is initially very low and slo
  • 2007 E.C., Q46 – Standard electrode potential for couple is +0.15V and that for the couple is -0.74V. These two couples in their standard state are connected to make a spontaneous reaction. The cell potential will be
  • 2006 E.C., Q49 – Which of the following reaction is NOT a redox reaction?
  • 2006 E.C., Q47 – The two standard electrode potentials involved in the nickel cadmium rechargeable cell are given below. NiO (s) + 2H S (l) + 2e →Ni(OH) (s) + 2OH 2 2 − 2 −E = 0 +0.49V Cd(OH) (s) + 2e →Cd(s) + 2OH (aq) 2 − E = 0 −0.76V C
  • 2005 E.C., Q74 – For the following hypothetical equation, in aqueous solution, what is the correct representation of the cell notation? A(s) + B (aq) _ A (aq) + B(s) 2+ 2+ A(s)∣A (aq)∣∣B (aq)∣B(s) 2+ 2+ B (aq)∣B(s)∣∣A (aq)∣A(s) 2+ 2+
2.5 Volatic Cells · read p. 115
  • 2018 E.C., Q57 – A metal pipeline buried underground is protected from corrosion by attaching a more reactive metal such as magnesium. Why does magnesium protect the iron pipe?
  • 2015 E.C., Q14 – Which one of the following reactions would occur spontaneously in an aqueous solution at 25°C? Assume that the initial concentrations of the dissolved species are all 1.0 M. Half reaction E°(V) Sn 2 + ( aq ) + 2 e - ➝ Sn
  • 2014 E.C., Q38 – Which of the following is true about galvanic cells used in commercial lead storage batteries? In lead storage batteries,
  • 2013 E.C., Q9 – One of the following is NOT a common application of silicon
  • 2013 E.C., Q53 – Which one of the following is NOT correct about electrodes and electrochemical cells?
  • 2013 E.C., Q59 – One of the following is NOT true about the effects of corrosion?
  • 2012 E.C., Q60 – When iron is 'galvanized', what metal is used to coat iron?
  • 2012 E.C., Q62 – The value of E° for the reaction Zn(s) + Cu^2+(aq) → Cu(s) + Zn^2+(aq) is 1.10 V. What is the value of Ecell when the concentrations of Cu^2+ and Zn^2+ are equal to 0.025 M?
  • 2011 E.C., Q42 – Features common to both galvanic and electrolytic cells include which of the following? I. Oxidation at the anode II. Can perform electrolysis III. Spontaneous
  • 2010 E.C., Q48 – In a voltaic cell, electrons flow from the___________ to the __________
  • 2009 E.C., Q56 – Which one of the following metal is used for galvanization of iron sheets?
  • 2009 E.C., Q64 – Devices in which oxidation- reduction reaction is induced by an electric current are called
  • 2008 E.C., Q64 – What is galvanized iron?
  • 2008 E.C., Q63 – What is the purpose of a salt bridge in an electrochemical cell?