Module 5: Redox and Electrode Potentials V1 Flashcards

1
Q

Write a balanced half equation for the oxidation of manganate(VII) ions to manganese(II) ions in acidic conditions.

A

Yeah, you have to remember this transformation.

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2
Q

Write a balanced half equation for the reduction of Iron(II) ions to Iron(III) ions in acidic conditions.

A

Yeah, you have to remember this transformation.

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3
Q

Write half equations under acidic conditions for the following. State whether the substance is being oxidised or reduced.

A
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4
Q

Write half equations under acidic conditions for the following. State whether the substance is being oxidised or reduced.

A
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5
Q

Write half equations under acidic conditions for the following. State whether the substance is being oxidised or reduced.

A
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6
Q

Write half equations under acidic conditions for the following. State whether the substance is being oxidised or reduced.

A
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7
Q

Write half equations under acidic conditions for the following. State whether the substance is being oxidised or reduced.

A
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8
Q

Write half equations under acidic conditions for the following. State whether the substance is being oxidised or reduced.

A
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9
Q

Write half equations under acidic conditions for the following. State whether the substance is being oxidised or reduced.

A
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10
Q

Write half equations under acidic conditions for the following. State whether the substance is being oxidised or reduced.

A
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11
Q

Write an overall redox equation using the two half-equations given.

A
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12
Q

Write half equations followed by the redox equation under acidic conditions for the following.

A
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13
Q

Write half equations followed by the redox equation under acidic conditions for the following.

A
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14
Q

Write half equations followed by the redox equation under acidic conditions for the following.

A
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15
Q

Write half equations followed by the redox equation under acidic conditions for the following.

A
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16
Q
A
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17
Q

What is the oxidising agent in manganate (VII) redox titrations

A

Manganate (VII) ions ✓

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18
Q

In manganate (VII) redox titrations, what solution is normally placed in the burette?

A

A solution containing Manganate (VII) ions is placed in the burette. ✓

i.e. potassium manganate ✓

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19
Q

Explain why Fe2+ pipetted into the conical flask with excess sulfuric acid in manganate (VII) redox titrations

A

To ensure acidic conditions ✓

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20
Q

Explain why Fe2+ pipetted into the conical flask with excess sulfuric acid instead of excess hydrochloric acid in manganate (VII) redox titrations

A
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21
Q

State the colour of Manganate (VII) ions

A

Purple. ✓

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22
Q

State the colour of manganese (II) ions

A

Pink. ✓

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23
Q

State the colour of the end-point in Manganate (VII) redox titrations

A

Pale pink. ✓

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24
Q

Suggest why the end point can appear colourless in Manganate (VII) redox titrations

A

Dilute solutions used. ✓

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25
Q
A
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26
Q
A
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27
Q

In thiosulfate/iodine redox titrations, what solution is normally placed in the burette?

A

Solution containing thiosulfate is placed in the burette. ✓

i.e. sodium thiosulfate ✓

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28
Q

In thiosulfate/iodine redox titrations what is normally placed in the conical flask containing Cu(II) ions (or other chemicals)

A

Excess I- is next added to the conical flask. ✓

i.e. KI ✓

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29
Q

In thiosulfate/iodine redox titrations, when excess I- is next added to the conical flask containing Cu(II) ions. State what observation can be made and give the species responsible for the observation made.

A

White precipipate - CuI ✓

Brown solution - I2 ✓

30
Q

In thiosulfate/iodine redox titrations, what reacts with the thiosulfate ions?

A

The thiosulfate is added from the burette and reacts with the I2 ✓

31
Q

In thiosulfate/iodine redox titrations, there would usually be a colour change from brown to yellow to colourless but this is difficult to see. What can be added as an indicator and state the colour of the resulting mixture.

A

Starch. ✓

Deep blue/black colour ✓

32
Q

A student is conducting a thiosulfate/iodine redox titration. State what they would observe at the end point.

A

Deep blue/black colour ✓

Sharply dissapears ✓

Colourless solution ✓

33
Q

A student is conducting a thiosulfate/iodine redox titration. What is the molar ratio of thiosulfate: iodine: copper(II) ions he needs to remember

A

2:1:2. ✓

Not always given in the exam.

34
Q
A
35
Q

Describe the composition of a “half-cell”

A

A half-cell comprises of an element in two different oxidation states. ✓

36
Q

Define what is meant by “Standard electrode potential of a half cell” and give the symbol for this.

A
37
Q

Define what is meant by the term “Electrochemical series”

A

lists the values from negative ✓ most reactive ✓ better reducing agents ✓

to more positive ✓ least reactive ✓ better oxidising agents ✓

38
Q

State the standard conditions used in half-cells.

A
39
Q
A
40
Q
A

don’t forget H+

41
Q

Define what is meant by the “the standard hydrogen half-cell “

A

Where E⦵ = 0.00V ✓

is used as the reference ✓

for the measurement of electrode potential values. ✓

42
Q

Define what is meant by “The standard electrode potential of a half-cell “

A

is the electromotive force (emf) of a half-cell ✓

compared with the standard hydrogen half-cell ✓

measured at 298K and 100kPa. ✓

43
Q

State the value of the cell potential, for the standard hydrogen half-cell.

A
44
Q

Write the equation for the electrode potential, E⦵, of hydrogen.

A
45
Q

In the electrochemical series, what type of redox process are reactions normally written in.

A

Reduction. ✓

46
Q

State the purpose, for the standard hydrogen half-cell.

A

Is used as the reference for the measurement of electrode potential values. ✓

47
Q

Draw a labelled half-cell for the standard hydrogen electrode.

A
48
Q

What is a electrochemical cell?

A

Two half cells are connected to make an electrochemical cell. ✓

49
Q

Below is a diagram of an electrochemical cell.

What are the charge carriers in the wire?

What are the charge carriers in the salt-bridge?

A

Wire: electrons

Salt-bridge: Ions

50
Q

What is the salt bridge composed of?

Explain why these chemicals are used?

A

filter paper soaked in KNO3 or NH4NO3. ✓

They do not react with either half-cell solution. ✓

51
Q

In an electrochemical cell, state and explain which electrode releases electrons.

A

The half-cell with the more negative E⦵ value. ✓

(equilibrium shifts left)

52
Q

In an electrochemical cell, state and explain which electrode gains electrons.

A

The half-cell with the more positive E⦵ value. ✓

(equilibrium shifts right)

53
Q

Give the equation required to calculate the cell potential

A
54
Q
A
55
Q
A
56
Q
A
57
Q
A
58
Q

Draw a labelled diagram based on the redox systems shown below.

A
59
Q

Write the overall cell reaction for the following two redox systems.

A
60
Q

Calculate the cell potential, for the electrochemical cell comprising of the two redox systems below

A
61
Q

Using the data given state and explain whether Cu will reduce Zn2+ to Zn?

A
62
Q

State three limitations in predicting feasibility using standard electrode potentials

A

Non-standard conditions used (changes in concentration shifts the equilibrium position). ✓

Slow rate of reaction. ✓

High activation energy for the reaction. ✓

63
Q
A
64
Q
A
65
Q

Will magnesium reduce copper (II) ions to copper? Suggest reasons why the reaction may not take place? Calculate the cell potential. The cell potential slowly changed, why.

A
66
Q

In an acid hydrogen fuel cell. State the transformation at the electrodes. Write half-equations for each transformation and combine the half equations to make an overall equation.

A
67
Q

In an alkali hydrogen fuel cell. State the transformation at the electrodes. Write half-equations for each transformation and combine the half equations to make an overall equation.

A
68
Q

Give three advantages of fuel cells:

A

H2O is the only product. ✓

Less CO2 produced, which is a green has gas. ✓

Greater efficiency. ✓

69
Q

Hydrogen is a flammable gas, and it is dangerous to transport. State how it can be stored.

A

As a liquid, under pressure. ✓

Adsorbed on the surface of a solid material. ✓

Absorbed within solid materials. ✓

70
Q
A