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Electrochemistry Test

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Last updated almost 5 years ago
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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
Question 1
1.

Calculate the e.m.f of the cell.

Question 2
2.

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
Question 3
3.

Write an equation for the spontaneous reaction that occurs

Question 4
4.

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

Question 5
5.

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.

Question 6
6.

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

Question 7
7.

Explain your answer to the previous question.

An excess of acidified potassium manganate(VII) was added to a solution containing V2+ (aq) ions.
Question 8
8.

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.

Question 9
9.

State the oxidation state of vanadium in this species

Question 10
10.

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.
Question 11
11.

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.
Question 12
12.

State the purpose of the salt bridge.

Question 13
13.

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

Section 3

Question 14
14.

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

Question 15
15.

The following cell has an EMF of +0.46 V.

Cu| Cu2+ || Ag+ | Ag

Which state is correct about the operation of the cell?

Question 16
16.

In this question, consider the data above.

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

Question 17
17.

In this question consider the data above.

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

Question 18
18.

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?

Question 19
19.

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

Question 20
20.

The most powerful oxidising agent in the table is:

Question 21
21.

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

Which of the following statements is not correct?