Topic 14- Redox II Flashcards Preview

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Flashcards in Topic 14- Redox II Deck (31)
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1
Q

What conditions are assumed at the standard electrode potential?

A

1.0 mol dm-3
100kPa
298K/25c
No current flowing

2
Q

Reducing agent is itself …….

A

oxidised

3
Q

Oxidising agent is itself ……

A

reduced

4
Q

Why is a high resistance voltmeter needed?

A

To stop the current from flowing in the circuit so you can measure the maximum Potential Difference (E)

5
Q

What is the salt bridge soaked in?

A

filter paper soaked in KNO3, potassium nitrate

unreactive with electrodes and solutions

6
Q

The most positive electrode will always undergo ….

A

reduction

7
Q

the most negative electrode will always undergo …..

A

oxidation

8
Q

When writing cell diagrams, which species are put next to the double solid line?

A

The most oxidised (inside)

so then the outermost species are most reduced

9
Q

The more ……. half cell is written on the right

A

positive

10
Q

What do the lines represent in a cell diagram?

A

the salt bridge = I I

Separation of phases e.g. solid and solution = I

11
Q

What is a , used for in cell diagrams?

A

Separates species in the same physical state

12
Q

If a system doesn’t include a metal that can act as an electrode then a ….. electrode must be used.

A

platinum

13
Q

What is the reference electrode and what is its potential?

A

A hydrogen electrode and = 0v

14
Q

Why do we use a reference electrode?

A

As to measure the potential difference we need 2 electrodes and must know 1 potential

15
Q

The potential of all electrodes are measured by comparing their potential to that of the standard ….. electrode

A

hydrogen

16
Q

What is the equation for the hydrogen electrode equilibrium?

A

H2 2H+ + 2e-

17
Q

When writing half equations the more oxidised is on the ….. and the more reduced is therefore on the …..

A

The more oxidised = left

The more reduced = right

18
Q

in the electrode system containing two ………. it is necessary to use a platinum electrode and both solutions must be of a …. concentration.

A

solutions, 1 mol

19
Q

How to calculate the EMF of the cell?

A
Ecell= E(right) - E(left)
Ecell= E(reduction) - E(oxidation)
20
Q

The more …… electrode potential is on the right

A

positive

21
Q

The more ……. half cell will always reduce (go forwards)

A

positive

22
Q

How do you know which direction to write a half-cell equation in?

A

Reduction is always forward reaction (left to right) in half-cell equations, electrons always added on LEFT side

23
Q

Oxidation always happens at the….. and the reduction always happens at the ……

A
Oxidation = Anode
Reduction= Cathode
24
Q

More reactive metal gives up its electrons and is …. ( becomes the anode where e-‘s flow from) and less reactive metal becomes the cathode

A

More reactive metals become the anode and is oxidised

25
Q

When drawing half cells the half-cell where oxidation happens (the ……) should always be on the ……

A

Oxidation happens = anode = left

26
Q

When drawing half cells the half-cell where reduction happens ~( the cathode) should always be on the ….

A

Reduction happens = cathode = right

27
Q

What is the role of the salt bridge? (2)

A

The salt bridge completes the circuit (1)

and allows ions to flow between half cells to balance the charges (1)

28
Q

When calculating the electrode potential the half equation that is more positive E goes …… and the more negative …….

A

E goes forward if more positive

backwards if more negative

29
Q

Write an equation with the two half cells:
Zn(aq)2+ + 2e- = Zn(s) -0.76
Cu(aq)2+ + 2e- = Cu(s) +0.34

A

Cu2+ + Zn(s) == Cu(s) + Zn2+

30
Q

Define the standard electrode potential?

A

The voltage measured under standard conditions when the half-cell is connected to a standard hydrogen electrode

31
Q

The standard H electrode is always found on the ….. (in diagrams)

A

LEFT