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Electrochemistry Test

Last updated almost 5 years ago
21 questions

Upper Sixth Electrochemistry Test

Formulae and equations
When you are writing formulae and equations, you need to write your answer in such a way that the computer will recognise your answer. Please following the following instructions:
- Separate all substances with a space (E.g. 4Na + 2O2 --> 2Na2O)
- No space between the stoichiometric number and the compound/ion/element
- The arrow must be formed like this --> It is two dashes and a greater than sign.
- Any charges must be placed in a round bracket, e.g. SO4(2-) for sulfate, H(+) for hydrogen ions, and e(-) for electrons.
- Do not put in state symbols unless asked.
Example: 2ClO3(-) + 12H(+) + 10e(-) --> Cl2 + 6H2O

Diagrams
One question will ask you to draw a diagram. Please draw it on paper, take a picture of it, send it to your computer, and upload it using the function. If you really want to draw it using your mouse, you can, but I definitely don't recommend it.

Marking
Your teacher will mark questions 7, 11, 12 and 13. These questions are written questions and a diagram.

Section 1

The cell represented below was set up under standard conditions

Pt | H2SO3 (aq) , SO42- (aq) || Fe3+ (aq), Fe2+ (aq) | Pt
1

Calculate the e.m.f of the cell.

1

Write a half equation for the oxidation process occuring at the negative electrode of this cell.

The cell represented below was set up under standard conditions

Pt | H2O2 (aq) , O2 (g) || IO3- (aq) , I2 (aq) | Pt
2

Write an equation for the spontaneous reaction that occurs

1

Give one reason why the e.m.f. of the cell changes when the electrodes are connected and a current flows.

1

State how, if at all, the e.m.f. of this standard cell will change if the surface area of each platinum electrode is doubled.

1

State how, if at all, the e.m.f. of this cell will change if the concentration of IO3- ions is increased.

2

Explain your answer to the previous question.

An excess of acidified potassium manganate(VII) was added to a solution containing V2+ (aq) ions.
1

Use the data given in the table at the top of the section to determine the vanadium species present in the solution at the end of this reaction.

1

State the oxidation state of vanadium in this species

1

Write a half-equation for its formation from V2+ (aq).

Section 2

In a test, aqueous iron(III) ions are reduced to aqueous iron(II) ions by iodide ions. This reaction could be used to provide electrical energy in a cell.
3

The standard electrode potential for the reduction of iron(III) ions into iron(II) ions can be measured by connecting a suitable electrode to a standard hydrogen electrode. Draw a clearly labelled diagram to show the components and reagents, including their concentrations, in this Fe(III)/Fe(II) electrode. Do not draw the salt bridge or the standard hydrogen electrode.

A salt bridge is used to complete the cell. This could be prepared using potassium nitrate solution and filter paper.
1

State the purpose of the salt bridge.

1

State one essential requirement of the soluble ionic compound used to make the salt bridge.

Section 3

1

Which ion cannot catalyst the reaction between iodide and peroxodisulfate (S2O82-)?
Use the table above to answer the question.

1

The following cell has an EMF of +0.46 V.

Cu| Cu2+ || Ag+ | Ag

Which state is correct about the operation of the cell?

1

In this question, consider the data above.

The e.m.f. of the cell Ag | Ag+ || Pb2+ |Pb is...

1

In this question consider the data above.

The e.m.f. of the cell Pt | H2 | H+ || Ag+ | Ag would be increased by...

1

A disproportionation reaction occurs when a species M+ spontaneously undergoes simultaneous oxidation and reduction. The table above contains E data for copper and mercury species.

Using these data, which one of the following can be predicted?

1

Based on the above data, which one of the following could reduce 0.012 mol of bromine to bromide ions?

1

The most powerful oxidising agent in the table is:

1

Use the data in the table above to answer this question.

Which of the following statements is not correct?