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Chemistry > Electrochemistry > Flashcards

Electrochemistry Flashcards

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1
Q

What is the purpose of the salt bridge?

A

To connect the two cells and to allow the ions to flow back towards the negative electrode

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2
Q

Which electrode is the positive electrode?

A

The cathode where reduction occurs.

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3
Q

Which electrode is the negative electrode?

A

The anode where oxidation occurs.

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4
Q

How to set up a cell diagram?

A

The lowest charges go on the outside

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5
Q

Why does the voltmeter have high resistance?

A

It has a very high resistance to stop a current flowing through the circuit to maximise the EMF produced.

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6
Q

What does a single line mean in a cell diagram?

A

Phase boundary

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7
Q

What does a double line in a cell diagram mean?

A

Salt bridge

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8
Q

What must you remember when drawing a cell diagram?

A

All the state symbols

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9
Q

Why is platinum used in an electrochemical cell?

A

It is very unreactive and can conduct electricity.

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10
Q

How do you separate species which are in the same phase in a cell diagram?

A

Use a comma

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11
Q

What is meant by the term ‘electrochemical series’?

A

List of electrode potentials in numerical order

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12
Q

What are the conditions for the hydrogen half cell potential to be 0?

A

100kpa 1mol 298K

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13
Q

Why would the actual EMF of a cell be different to the calculated one?

A

Not under standard conditions

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14
Q

Why should a hydrogen fuel cell be used instead of an internal combustion engine?

A

More of the potential energy is released from a fuel cell rather than an internal combustion engine.

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15
Q

Why should a hydrogen fuel cell be used instead of an internal combustion engine?

A

More of the potential energy is released from a fuel cell rather than an internal combustion engine.

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16
Q

Why would an electrode be rubbed with sandpaper prior to use?

A

To remove the oxide layer

17
Q

What is a reducing agent?

A

An electron donor.

18
Q

What is an oxidising agent?

A

An electron acceptor

19
Q

Why cant some cells be recharged?

A

The reaction is not reversible

20
Q

If it asks for the discharge equation what equation is it?

A

Just the normal oxidation then reduction

21
Q

If it asks for a charging reaction what is the final equation

A

The one that normally gets oxidised is reduced and the one that normally gets reduced is oxidised

22
Q

Why is the standard electrode potential for a hydrogen electrode 0?

A

By definiton

23
Q

What salt solution should the salt bridge be dipped in and why?

A

Potassium nitrate and it should not react with either the electrodes or electrode solutions

24
Q

If the system does not have a solid conducting surface, why should a platinum electrode be used?

A

unreactive and can conduct electricity

25
Q

What is the standard electrode potential for strong reducing agents?

A

Most negative as they are being oxidised so losing electrons

26
Q

What is the standard electrode potential for strong oxidising agents?

A

Most positive as they are being reduced so gaining electrons

27
Q

What happens if you increase the concentration of the reactants?

A

The Ecell value will increase

28
Q

What happens if you decrease the concentration of the reactants?

A

The Ecell value will decrease

29
Q

How will temperature effect the value of Ecell?

A

If the temperature is increased then the value of Ecell will decrease the value of Ecell.

30
Q

What is a fuel cell?

A

A fuel cell is a cell which uses energy from the reaction of a fuel with oxygen to create a voltage.

31
Q

Why does a fuel cell maintain a constant voltage over a period of time?

A

The concentrations of the reactants and the products doesn’t change as they are constantly being replenished.

32
Q

Why are high temperatures and high pressures used in fuel cells?

A

High temperature is needed because at standard conditions the Ecell value is too small, even though the forward reaction is exothermic. Therefore a high pressure is used as there are less moles of gaseous species on the right hand side so equilibrium shifts to the right.

33
Q

What are the advantages of hydrogen fuel cells?

A

Less pollution from CO2
Hydrogen is readily available
good efficiency

34
Q

What are the disadvantages of fuel cells?

A

expensive
storing and transporting hydrogen could be dangerous
toxic chemicals are used in their production

35
Q

What components are needed for a standard hydrogen cell?

A

1 molar HCl
hydrogen
100kPa
platinum electrode

36
Q

Why will the EMF of a cell reach zero?

A

The concentrations of the reactants and products are equal or the reactants have been used up.

37
Q

How could recharging a cell lead to increased CO2 in the atmosphere?

A

power plant energy could come from burning fossil fuels

Chemistry (32 decks)

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