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Electron Transfer Reactions (DP IB Chemistry: SL): Exam Questions

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11 mark

Which row correctly describes oxidation and reduction in terms of the transfer of electrons and changes in oxidation state? 

 

Transfer of electrons

Change in oxidation state

 

oxidation

reduction

oxidation

reduction

A

gain

loss

increase

decrease

B

loss

gain

increase

decrease

C

loss

gain

decrease

increase

D

gain

loss

decrease

increase

    Choose your answer

    21 mark

    The heptahydrate mineral of magnesium sulfate is used in Epsom Salts for preparing therapeutic baths. Magnesium sulfate is also used in some medical applications.

    What is the overall charge of MgSO4?

    • -2

    • +2

    • +7

    • 0

    Choose your answer

    31 mark

    Which row describes the most common oxidation numbers of fluorine, oxygen and hydrogen in compounds? 

     

    F

    O

    H

    A

    +7

    -1

    -1

    B

    +1

    +2

    +1

    C

    -7

    -1

    -1

    D

    -1

    -2

    +1

      Choose your answer

      41 mark

      Solutions containing chlorate(I) ions decompose on heating as shown:                    

      3ClO-  →  ClO3- + 2Cl- 

      Which row is correct for the oxidation state of the chlorine in each ion? 

       

      ClO-

      ClO3-

      Cl-

      A

      +1

      +5

      -1

      B

      +1

      +3

      +1

      C

      -1

      +5

      -1

      D

      -1

      +3

      +1

        Choose your answer

        51 mark

        A student added a solution of iodine to a solution of sodium bromide. Which statement correctly describes what happens?

        • No reaction occurs

        • The bromide ions are oxidised

        • The iodine atoms are oxidised

        • Both the bromide and iodide ions undergo changes in their oxidation state

        Choose your answer

        61 mark

        In which of the following reactions is the change in oxidation number the smallest for nitrogen?

        • N2 + 3H2 → 2NH3

        • 3Mg + N2 → Mg3N2

        • 4NH3 + 5O2 → 4NO + 6H2O

        • 2NO + O2 → 2NO2

        Choose your answer

        71 mark

        Titanium dioxide is obtained from the ore ilmenite, Fe(II)TiO3. 

        FeTiO3 → TiO2 

        What is the change in the oxidation number of titanium in the reaction?

        • +4 to +5

        • +3 to +4

        • No change in oxidation number occurs

        • +6 to +4

        Choose your answer

        81 mark

        Below are four statements about voltaic and electrolytic cells.

        Identify the statement that is correct for voltaic cells but not for electrolytic cells

        • An electrolyte is needed in the cell

        • Ions are moving in the electrolyte

        • Oxidation occurs at the anode

        • Electrons flow from the negative to the positive electrode 

        Choose your answer

        91 mark

        What substance will be obtained at the positive electrode (anode) when molten KBr is electrolysed?

        • K(l)

        • Br(l)

        • Br2(l)

        • K(s)

        Choose your answer

        101 mark

        The compound ‘leaf alcohol’ is partly responsible for the smell of new-mown grass.

        CH3CH2CH=CHCH2CH2OH

        leaf alcohol

        What product will be formed when ‘leaf alcohol’ is oxidised using an excess of acidified K2Cr2O7 (aq) under reflux?

        • CH3CH2CH(OH)CH(OH)CH2CO2H

        • CH3CH2COCOCH2CO2H

        • CH3CH2CH=CHCH2CO2H

        • CH3CH2CO2H and HO2CCH2CO2H

        Choose your answer

        111 mark

        Which of the alcohols shown below will decolourise acidified potassium manganate(VII)?

        I.    CH3CH2CH2CH2OH

        II.   CH3CH(OH)CH2CH3

        III.   (CH3)3CCH2OH

        • I and II only  

        • I and III only  

        • II and III only 

        • I, II and III

        Choose your answer

        121 mark

        What can be produced when an aqueous solution of butan-2-ol is oxidised under suitable conditions?

        I. butanone

        II. butanoic acid

        III. butanal

        • I, II and III

        • I and II only 

        • II and III only 

        • I only

        Choose your answer

        131 mark

        What is the product of the reaction between propanone and sodium borohydride, NaBH4?

        • propan-1-ol

        • propan-2-ol

        • propanoic acid

        • pentanal

        Choose your answer

        14
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        Propanone is made by a two stage process. 

        The second stage involves oxidation. 

        Propene    →     X   →   Propanone

        What is the functional group of compound X?

        • COOH

        • OH

        • COO

        • C=O

        Choose your answer

        15
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        4-methylpentanal can be formed by the oxidation of 4-methylpentan-1-ol.

        Which reagent is used as an oxidising agent for this conversion?

        • NaBH4

        • NaOH

        • K2Cr2O7

        • LiAlH4

        Choose your answer

        11 mark

        The chemistry of the Group VII elements often involves redox processes.

        Which of the following statements is correct?

        • Bromine can oxidise chloride ions

        • Iodide ions are the weakest reducing agent of the first four Group VII ions

        • In reactions with water, chlorine is oxidised and reduced

        • Fluorine is a weaker oxidising agent than chlorine

        Choose your answer

        21 mark

        In which of the following reactions is the species shown in bold acting as an oxidising agent?

        • Cr2O72- + 8H+ + 3SO32- → 2Cr3+ + 4H2O + 3SO42-

        • Mg + Fe2+ → Mg2+ + Fe

        • Cl2 + 2Br- → 2Cl- + Br2

        • Fe2O3 + 3CO → 2Fe + 3CO2

        Choose your answer

        31 mark

        In which compound are there two different elements with the same oxidation number?

        • Mg(OH)2

        • Na2SO4

        • HClO

        • NH4Cl

        Choose your answer

        41 mark

        When sulfuric acid and sodium iodide react, one of the reactions that takes place is shown by the equation below: 

        8NaI  +  9H2SO4  →  8NaHSO4  +  4I2  +  H2S  +  4H2O 

        Which species has been oxidised in this reaction?

        • I−

        • SO42−

        • Na+

        • H+

        Choose your answer

        51 mark

        The following reaction can be used to determine the mass of titanium dioxide in an ore. 

        3TiO2  +  4BrF3  →  3TiF4  +  2Br2  +  3O2 

        Which element increases in oxidation number in this reaction?

        • fluorine

        • bromine

        • titanium

        • oxygen

        Choose your answer

        61 mark

        In which reaction does hydrogen behave as an oxidising agent?

        • 2Na  +  H2  →  2NaH

        • N2  +  3H2  →  2NH3 

        • H2  +  Cl2  →  2HCl

        • C2H4  +  H2  →  C2H6

        Choose your answer

        71 mark

        When solid potassium halides are added to concentrated sulfuric acid, the following reactions take place: 

        Reaction 1:

        2KBr  +  2H2SO4  →  K2SO4  +  SO2  +  Br2  +  2H2O

        Reaction 2:

        8KI  +  5H2SO4  →  4K2SO4  +  H2S  +  4I 2  +  4H2O

        Reaction 3:

        2KCl  +  H2SO4  →  K2SO4  +  2HCl

        In each reaction, what is the largest change in the oxidation number of sulfur? 

         

        Reaction 1

        Reaction 2

        Reaction 3

        A

        1

        4

        1

        B

        2

        4

        0

        C

        2

        8

        0

        D

        4

        8

        1

          Choose your answer

          81 mark

          What is formed at the electrodes during the electrolysis of molten potassium iodide? 

           

          Positive electrode

          Negative electrode

          A

          K+

          I-

          B

          K

          I2

          C

          I-

          K+

          D

          I2

          K

           

            Choose your answer

            91 mark

            Below is a diagram of a voltaic cell. When the cell is running, what is happening in the salt bridge?

            Diagram of an electrochemical cell with zinc and copper electrodes in zinc sulphate and copper sulphate solutions, connected by a voltmeter.

            • K+ ions flow to the zinc half-cell and NO3− ions flow to the copper half-cell

            • K+ ions flow to the copper half-cell and NO3− ions flow to the zinc half-cell

            • K+ and NO3− ions flow to the copper half-cell

            • K+ and NO3− ions flow to the zinc half-cell

            Choose your answer

            101 mark

            2.30 g of ethanol was oxidized using excess aqueous acidified potassium dichromate(VI). The desired organic product was collected by immediate distillation.

            If the percentage yield of the product was 50.0%, what mass of product was collected?

            • 1.10 g

            • 1.15 g

            • 2.20 g

            • 2.30 g

            Choose your answer

            111 mark

            Which alcohol gives only one possible oxidation product when warmed with dilute acidified potassium dichromate(VI)?

            • butan-1-ol

            • butan-2-ol

            • 2-methylpropan-1-ol

            • 2-methylpropan-2-ol

            Choose your answer

            121 mark

            Hydroxyethanal has the structural formula HOCH2CHO.

            In an experiment hydroxyethanal is heated under reflux with an excess of acidified potassium dichromate(VI) until no further oxidation takes place.

            What is the skeletal formula of the organic product formed in the experiment?

            10-2-m-q9-ib-chemistry-mcqs

              Choose your answer

              131 mark

              What is formed when butanone is heated under reflux with a solution of NaBH4?

              • CH3CH2CHCH2

              • CH3CH2CH2CH2OH

              • CH3CHOHCH2CH3

              • CH3CH2CH2CHO

              Choose your answer

              11 mark

              When heated ammonium nitrate, NH4NO3, can decompose explosively.

              NH4NO3 → N2O + 2H2O 

              The nitrogen atoms in NH4NO3 have different oxidation numbers. 

              What are the changes in oxidation number for the two nitrogen atoms during this reaction?

              • +4, –4

              • –2, –4

              • +4, –6

              • +2, +6

              Choose your answer

              21 mark

              In winemaking, to prevent the oxidation of ethanol by air, sulfur dioxide (SO2) is added. In order to calculate the amount of SO2, a sample is titrated with iodine (I2). The reaction is a one to one ratio for SO2 and I2 to produce H2SO4 as well as another product. 

              What is the change in the oxidation number of sulfur in this reaction?

              • +2 to +6

              • +4 to +6

              • +2 to +4

              • +4 to +5

              Choose your answer

              31 mark

              20 cm3 of a 0.60 mol dm–3 solution of thallium nitrate (TlNO3) requires 40 cm3 of 0.20 mol dm–3 acidified ammonium metavanadate (NH4VO3) to produce Tl3+(aq) ions. 

              Vanadium is the only element reduced in this reaction. What is the oxidation number of the reduced vanadium?

              • +1

              • +2

              • +3

              • +4

              Choose your answer

              41 mark

              If a solution contains both bromine and chlorine, BrO3– ions are produced. 

              The reactions leading to the production of BrO3– ions are shown below: 

              Reaction 1:     Br2  +  H2O  →  HBr  +  HBrO 

              Reaction 2:     3HBrO  +  Cl2  →  2Cl –  +  BrO3–  +  Br2  +  3H+ 

              Which statements are correct?

              I.Chlorine is reduced in reaction 2

              II.Bromine is reduced in both reaction 1 and reaction 2

              III.Bromine is oxidised in both reaction 1 and reaction 2

              • I and II only 

              • I and III only

              • II and III only

              • I, II and III

              Choose your answer

              51 mark

              If a dilute acid is added to an aqueous solution containing nitrite ions, NO2–, two different nitrogen compounds are released as gases. 

              2H+(aq)  +  2NO2–(aq)  →  H2O(l)  +  NO(g)  +  NO2(g) 

              Which statements correctly describe the process? 

              I. The H+(aq) ion is oxidised by NO2–(aq).

              II. Some nitrogen atoms are oxidised, and some nitrogen atoms are reduced.

              III. The H+(aq) ion acts as a catalyst.

              • I and II only 

              • II only

              • II and III only

              • I, II and III

              Choose your answer

              61 mark

              A voltaic cell consisting of zinc and silver is set up. The following overall reaction takes place:

              Zn(s)   +  2Ag+(aq)  →  Zn2+(aq)  +  2Ag(s)

              What are the correct half-equations at each electrode? 

               

              Anode

              (negative electrode)

              Cathode

              ( positive electrode)

              A

              Ag(s) → Ag+ (aq)  + e-

              Zn2+(aq) + 2e- → Zn(s)

              B

              Ag+(aq)  + e-→ Ag(s)

              Zn(s) → Zn2+(aq) + 2e-

              C

              Zn(s) → Zn2+(aq) + 2e-

              Ag+(aq)  + e-→ Ag(s)

              D

              Zn2+(aq) + 2e- → Zn(s)

              Ag(s) → Ag+(aq)  + e-

                Choose your answer

                71 mark

                Which statement about the movements of electrons in voltaic cells is correct?

                • Electrons flow through the external wire from the cathode (positive electrode) to the anode (negative electrode) 

                • Electrons flow through the external wire from the anode (negative electrode) to the cathode (positive electrode) 

                • Electrons flow through the salt bridge from the oxidizing agent to the reducing agent 

                • Electrons flow through the salt bridge from the reducing agent to the oxidizing agent 

                Choose your answer

                81 mark

                What are the products when molten magnesium chloride is electrolysed using graphite electrodes? 

                 

                Product at cathode

                (negative electrode)

                Product at anode

                ( positive electrode)

                A

                magnesium

                chlorine

                B

                chlorine

                magnesium

                C

                magnesium ions

                chloride ions

                D

                chloride ions

                magnesium ions

                  Choose your answer

                  91 mark

                  Use the information given about four reactions of metals to determine the order of reactivity from most reactive to least reactive

                     W (s) + X2+ (aq) → W2+ (aq) + X (s)

                     Y (s) + W2+ (aq) → No Reaction

                     X (s) + Y2+ (aq) → X2+ (aq) + Y (s)

                     Z (s) + Y2+ (aq) → No Reaction

                  • W > Y > X > Z

                  • X > W > Z > Y

                  • Z > Y > W > X

                  • W > X > Y > Z

                  Choose your answer

                  101 mark

                  Which statements about voltaic cells are correct? 

                  I.   A redox reaction takes place which produces electrical energy.

                  II.   At the cathode, an oxidation reaction occurs.

                  III.   Electrons move from the anode to the cathode.

                  • I and II only  

                  • I and III only  

                  • II and III only 

                  • I, II and III

                  Choose your answer

                  111 mark

                  An organic compound Y with molecular formula C5H12O, is oxidised to compound Z with molecular formula C5H10O2.

                  What could be the structural formula of Y?

                  I. CH3(CH2)4OH

                  II. CH3CH2CH(CH2OH)CH3

                  III. CH3C(CH3)2CH2OH

                  • I and II only

                  • I and III only

                  • II and III only

                  • I, II and III only

                  Choose your answer

                  121 mark

                  A number of alcohols with the formula C4H10O are separately oxidised. Using 7.41 g of the alcohols a 50% yield of organic product is achieved.

                  What mass of product could be obtained?

                  I. 4.41 g of butanoic acid.

                  II. 4.41 g of 2-methylpropanoic acid.

                  III. 3.61 g of butanone.

                  • I and II only

                  • I and III only

                  • II and III only

                  • I, II and III

                  Choose your answer

                  13
                  Sme Calculator                  1 mark

                  Which alcohol could not be produced by the reduction of an aldehyde or a ketone?

                  • 2,2-Dimethylbutan-1-ol

                  • Propan-2-ol

                  • 3-Methylpentan-3-ol

                  • 2-Methylpentan-3-ol

                  Choose your answer

                  14
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                  Which molecule(s) can be both reduced by sodium borohydride, NaBH4, and oxidised by warm acidified potassium dichromate (VI)? 

                  I. CH3CHBr(CH3)2CCHO

                  II. CH3CHOHCH2CH3

                  III. (CH3)3CCHO

                  • I and II only 

                  • I and III only 

                  • II and III only 

                  • I, II and III 

                  Choose your answer