9.2.4 Oxidation- Reduction

2002 - Q4

Which statement concerning galvanic cells is correct?

(A) Oxidation occurs at the anode

(B) They are also known as electrolytic cells

(C) The cathode is assigned a negative charge

(D) An external power source must be present

2003 - Q13

A student performed three tests to investigate the relative activity of metals. In each test a metal strip was placed in a solution containing ions of a different metal. The results are shown in the diagrams.

What is the order of activity of the metals, based on these results?

(A) X > Z > Y

(B) Y > X > Z

(C) Z > Y > X

(D) Z > X > Y

2001 - Q18 (6 marks)

A galvanic cell was made by connecting two half-cells. One half-cell was made by putting a copper electrode in a copper (II) nitrate solution. The other half-cell was made by putting a silver electrode in a silver nitrate solution. The electrodes were connected to a voltmeter as shown in the diagram.

(a) Complete the above diagram by drawing a salt bridge (1 mark)

(b) Using the standard potentials table in the data sheet, calculate the theoretical voltage of this galvanic cell. (2 marks)

(c) A student removes the voltmeter from the circuit and replaces it with an electrical generator. The generator causes the copper electrode to increase in mass.

Explain, using an equation, why the copper electrode will increase in mass. (3 marks)

2001 - Q19 (7 marks)

Name ONE type of cell, other than the dry cell or the lead-acid cell, you have studied.

Evaluate it in comparison with either the dry cell or lead-acid cell, in terms of chemistry and the impact on society. Include relevant chemical equation in your answer.

2004 - Q14

Four metals Pb, x, y and z, were connected in pairs and the voltage was recorded.

The results obtained are set out in the table.

What is the order of increasing ease of oxidation of the metals?

(A) z, y, Pb, x

(B) Pb, x, y, z

(C) x, y, Pb, z

(D) x, Pb, y, z

2004 - Q15

Diagram A shows a dry cell. Diagram B shows a lead-acid cell.

2005 - Q5

An electrochemical cell is set up as shown in the diagram.

2003 - Q19 (3 marks)

(a) Identify the cathode in this diagram (1 mark)

(b) Write the net redox equation for the cell reaction, and calculate the cell potential (E°).

2004 - Q19 (6 marks)

The following experiment was performed to investigate the relative activity of metals.

The beaker initially contained 250.0 mL of 0.050 M copper sulfate solution.

After several hours the dark blue colour of the solution had become lighter and a red-brown deposit had formed on the piece of zinc metal.

(a) Account for the changes observed. Provide a balanced oxidation–reduction equation in your answer. (3 marks)

(b) The red-brown deposit was removed from the piece of zinc metal and dried. It was found to weigh 0.325 g. Calculate the concentration of copper sulfate solution remaining in the beaker. (3 marks)

2005 - Q19 (4 marks)

You have studied one of the cells shown below.

Choose ONE of the cells and answer parts (a) and (b).

(a) State ONE environmental impact associated with the cell you have chosen. (1 mark)

(b) Describe the chemistry of the cell you have chosen. (3 marks)

2007 - Q3

In a galvanic cell, what is the pathway of electron flow?

Direction Medium

(A) anode to cathode salt bridge

(B) anode to cathode external wire

(C) cathode to anode salt bridge

(D) cathode to anode external wire

2007 - Q5

The diagram represents a cell in which two metals have been placed in a solution containing their respective metallic ions. The metals are connected to a voltmeter.

Which of the following combinations of metals would produce the highest reading on the voltmeter?

(A) Tin and zinc

(B) Copper and zinc

(C) Copper and silver

(D) Magnesium and lead

2006 - Q19 (7 marks)

A student was asked to perform a first-hand investigation to measure the difference in potential of various combinations of metals in an electrolyte solution. The student was provided with three metals: aluminium, zinc and silver; and three electrolyte solutions: aluminium nitrate, zinc nitrate and silver nitrate.

(a) Identify which combination of the metals supplied should give the highest potential difference. (1 mark)

(b) Sketch and label a diagram of an experimental setup that the student could use with the combination of metals identified in part (a). (2 marks)

(c) Write a balanced chemical equation for the overall reaction for the metals identified in part (a), and calculate the expected potential difference. (2 marks)

(d) The measured potential difference obtained varied from the theoretical value. Outline steps the student could have taken to minimise this variation. (2 marks)

2007 - Q20 (4 marks)

The diagram represents a typical car battery.

As the battery discharges, the following half reactions occur:

Pb(s) + SO4 2- (aq) → PbSO4 (s) + 2e–

PbO2(s) + SO4 2- (aq) + 4H+(aq) + 2e– → PbSO4(s) + 2H2O(l)

(a) Identify the anode, then write the equation that represents the overall chemical reaction (2 marks)

(b) Explain one benefit of car batteries lasting several years/ (2 marks)

2008 - Q13

2009 - Q9

One test used for random breath testing in NSW involved crystals of potassium dichromate reacting with ethanol. In this reaction the orange dichromate ion, Cr2O7 2− , changes to the green chromium ion, Cr 3+. Which statement is true for this reaction?

(A) Chromium has lost electrons and reached a lower oxidation state.

(B) Chromium has lost electrons and reached a higher oxidation state.

(C) Chromium has gained electrons and reached a lower oxidation state.

(D) Chromium has gained electrons and reached a higher oxidation state.

2010 - Q12

In which of the following reactions does the metal atom show the greatest change in oxidation state?

(A) MnO4 − to Mn 2+

(B) MnO2 to Mn(OH)3

(C) PbO2 to PbSO4

(D) VO2 + to VO 2+

2008 - Q25 (5 marks)

A galvanic cell under standard conditions is represented below.

(a) On the diagram, clearly label the anode, the cathode and the direction of electron flow. (1 mark)

(b) Write a balanced net ionic equation for the overall cell reaction. (1 mark)

(c) Calculate the standard cell potential (E−°). (1 mark)

(d) Explain any colour changes observed in this cell as the reaction proceeds. (2 marks)

2009 - Q26 (7 marks)

An electrochemical cell is constructed using two half cells. One half cell consists of an inert platinum electrode and a solution of Fe 2+ and Fe 3+. The other half cell consists of a lead electrode and a solution of Pb 2+. Current will flow from one electrode to the other electrode when the cell is completed using a voltmeter and a salt bridge.

(a) Write relevant half equations and a balanced net ionic equation for the overall cell reaction. (2 marks)

(b) Calculate the standard cell potential (E−° ). (1 mark)

(c) Identify the anode, cathode, metals and ions by labelling the following diagram. (3 marks)

(d) Identify an appropriate electrolyte to use in the salt bridge. (1 mark)

2010 - Q13

The diagram shows a galvanic cell.

Which of the following metals (M) acting as an anode would produce the lowest theoretical potential for the cell?

(A) Calcium

(B) Copper

(C) Iron

(D) Manganese

2011 - Q12

A table of redox couples and their standard reduction potentials is shown.

Redox couple Ε−°

Ag+ /Ag 0.80 V

Cd2+ /Cd −0.40 V

Pd2+ /Pd 0.92 V

Ni2+ /Ni −0.24 V

Which of the following ranks the metals in decreasing order of their electrochemical activity?

(A) Ni > Cd > Ag > Pd

(B) Pd > Ag > Cd > Ni

(C) Pd > Ag > Ni > Cd

(D) Cd > Ni > Ag > Pd

2010 - Q27 (2 marks)

The diagram shows a particular cell with relevant half equations.

Identify the anode, cathode and electrolyte for this cell.

2011 - Q24 (7 marks)

A galvanic cell was constructed as shown in the diagram.

(a) Calculate the standard cell potential. In your answer, include a net ionic equation for the overall cell reaction. (2 marks)

(b) After a period of time, a solid deposit that had formed on the copper electrode was removed and dried. The deposit had a mass of 0.395 g.

(i) Calculate the final mass of the nickel electrode. (3 marks)

(ii) Calculate the final concentration of the nickel (II) nitrate solution. (2 marks)

2012 - Q13 - 14

This equation represents a common redox reaction.

(13) What is the oxidising agent in the reaction?

(A) H+

(B) Cr 3+

(C) Fe 2+

(D) Cr2O7 2–

(14) What is the value of E− cell ° for the reaction?

(A) 0.59 V

(B) 0.92 V

(C) 1.90 V

(D) 2.13 V

2013 - Q12

An experiment was set up as shown.

Which of the following statements is correct?

(A) The chlorine gas is the anode.

(B) The zinc electrode is the anode.

(C) The platinum electrode is the anode.

(D) There is no anode because there is no salt bridge.

2014 - Q16

In which of the following reactions is the metal species reduced?

(A) 2FeCl2(aq) + Cl2(g) → 2FeCl3(aq)

(B) CuS(s) + O2(g) → Cu(s) + SO2(g)

(C) 2Al(OH)3(aq) → Al2O3 (s) + 3H2O(l)

(D) Ca(s) + 2HCl(aq) → CaCl2(aq) + H2(g)

2014 - Q17

What is the standard cell potential for the reaction of 1.0 mol L−1 acidified potassium dichromate (K2Cr2O7 (aq)) with aqueous sulfur dioxide (SO2(aq) ) under standard conditions?

(A) 1.20 V

(B) 1.52 V

(C) 2.24 V

(D) 3.20 V

2013 - Q29 (2 marks)

Consider this chemical equation.

2Cl – (aq) + Br2(l) → 2Br – (aq) + Cl2(g)

Will the reaction occur spontaneously? Justify your response.

2014 - Q28 (5 marks)

A galvanic cell has been constructed as shown in the diagram.

(a) Explain the colour change in the copper half-cell as the reaction proceeds. (2 marks)

(b) The theoretical standard potential for this galvanic cell is 2.02 V. Identify metal X and justify your answer. (3 marks)

2015 - Q23 (4 marks)

Explain how the structure and chemistry of ONE of the following cells determines its cost and practicality.

• button cell

• fuel cell

• vanadium redox cell

• lithium cell

• liquid junction photovoltaic device (eg the Gratzel cell)

Name of cell:

2016 - Q21 (5 marks)

A student set up the following galvanic cell.

(a) On the diagram clearly indicate the direction of electron flow. (1 mark)

(b) Complete the following table for this galvanic cell. (4 marks)

Anode half equation

Cathode half equation

Overall cell equation

Overall cell potential

2015 - Q4

What happens to Fe 2+ in the following reaction?

Sn 4+ + Fe 2+ ---> Sn 3+ + Fe 3+

(A) It undergoes oxidation and gains electrons.

(B) It undergoes reduction and gains electrons.

(C) It undergoes oxidation and loses electrons.

(D) It undergoes reduction and loses electrons.

2015 - Q7

A diagram of a simple cell is shown.

Which of the following occurs when the cell is in operation?

(A) Silver ions are formed in solution.

(B) The copper electrode loses electrons.

(C) Electrons travel through the electrolyte.

(D) The copper electrode increases in mass.

2016 - Q16

An electrochemical cell has the following structure.

This particular cell can be represented as:

Q | Q2+ | | R2+ | R

Which of the following cells would produce the highest cell potential at standard conditions?

(A) Mg | Mg2+ | | Fe2+ | Fe

(B) Al | Al3+ | | Cu2+ | Cu

(C) Zn | Zn2+ | | Pb2+ | Pb

(D) Ni | Ni2+ | | Ag+ | Ag

2017 - Q10

The diagrams show a dry cell and a lead-acid cell. The electrodes are labelled X and Y.

When either cell is connected to supply energy, which row of the table correctly describes the electrodes and their charges?

2017 - Q11

Consider the following redox reaction.

Which of the following occurs when the cell is in operation?

(A) Silver ions are formed in solution.

(B) The copper electrode loses electrons.

(C) Electrons travel through the electrolyte.

(D) The copper electrode increases in mass.

Barker College Chemistry Department

Past HSC Chemistry Questions