Electrochemistry

Question 1

What are electrochemical cells made up of?

Answer 1

Two half cells

Question 2

What is a half cell?

Answer 2

A metal in a solution of its ions

Question 3

What happens if there are two ions in the solution

Answer 3

Platinum is used as it is inert and a good conductor

Question 4

What is the voltmeter used for?

Answer 4

To determine the voltage between the two half cells (calculating an emf value)

Question 5

What is a salt bridge used for

Answer 5

The flow of electrons

Question 6

How is a salt bridge made? Give an example -

Answer 6

Filter paper is dipped into a solution of KNO3 and folded into both half cells.

Question 7

What is the flow of electrons in a chemical cell?

Answer 7

More reactive to less reactive

Question 8

What order are half cell equations written in when shown in question?

Answer 8

Reduction

Question 9

What is the acronym for working out the order of the equation?

Answer 9

NO PRoblem
Negative Oxidation
Positive Reduction
Therefore the forward reaction is reduction so reduction goes first

Question 10

Describe a standard hydrogen electrode (SHE)

Answer 10

Two half cells
1st half cell - H+ ions as solution containing a platinum electrode, H2 is also instrted into the half cell at a pressure of 1000kPa and 298K
2nd half cell - copper in a solution of Cu2+ ions
Including a salt bridge

Question 11

What are the conditions for the standard hydrogen electrode

Answer 11

Pressure - 1000kPa, 298K
Concentration of ions - 1.00 moldm-3

Question 12

What is the voltage of a standard hydrogen electrode

Answer 12

0.0 volts

Question 13

What is the electrochemical series

Answer 13

A list of written half equations and their potential difference (voltage)

Question 14

What is the strongest oxiding agent if the values are positive at the top and negative at the bottom? Why?

Answer 14

The top value is the strongest oxidising agent as it is most positive so requires an electron more

Question 15

What is the strongest reading agent if the values at the top are positive and negative at the bottom why?

Answer 15

The bottom is the strongest reducing agent as it already has a negative charge so doesn’t need any more electrons

Question 16

What side of the equation are the ions or atoms reduced?

Answer 16

The right side eg.
Zn in the equation Zn2+ + 2e- = Zn

Question 17

What is the equation for E cell?

Answer 17

Eright - Eleft
Or
Ereduction - Eoxidation

Question 18

What is the key thing to remember when writing a cell notation?

Answer 18

ROOR
Reduction on the outside, oxidation on the inside
Include state symbols
Double line for salt bridge
Commas if the same state symbol
Lines for a change in state

Question 19

How do you test if the compound or ion will react with another compound or ion

Answer 19

Write out the equation using NO PRoblem, if the compounds or ions are on the same side they WILL react with each other. You can work it out by using the E0 equation (if it’s positive this shows they react)

Question 20

What is a benefit of non-rechargeable batteries

Answer 20

Cheaper short term

Question 21

What is an example of a non rechargeable battery?

Answer 21

AA battery

Question 22

What is a benefit of rechargeable batteries?

Answer 22

Last longer so cheaper long term

Question 23

What is an example of a rechargeable battery?

Answer 23

Phone, phone charger, iPad ect.

Question 24

What are the two electrodes in a rechargeable battery?

Answer 24

Electrode A - lithium cobalt oxide
Electrode B - graphite
Electrolyte - lithium salt dissolved in organic solvent

Question 25

What are the half equations at each electrode?

Answer 25

Li+ + e- = Li Li+ + CoO2 + e- = Li+[CoO2]-

Question 26

What is the equation of discharge for a rechargeable battery and how to work it out

Answer 26

Work out which equation is oxidation and which is reductio. Swap round the oxidation equation which is Li+ To make this equation - Li + CoO2 = Li+[CoO2]-

Question 27

Ho do you work out the equation for rechargeable batteries when they are recharging?

Answer 27

Flip the discharge equation round

Question 28

What are the advantages of fuel cells?

Answer 28

No harmful emissions. - only produces water Oxygen is easily obtained Efficient process Don’t need to be recharged as long as there is a sufficient supply

Question 29

What are the disadvantages of fuel cells?

Answer 29

Hydrogen gas is highly flammable Therefore to take safety measures when transporting it is expensive

Question 30

What is the process of a hydrogen fuel cell charging?

Answer 30

Hydrogen gas is inserted into the cell and diffused into the platinum electrode The hydrogen is then passed through the wire creating a voltage which is the power to fuel a car The hydrogen then mixes with OH- coming in from the right side of the cell to create water The water then diffuse across the electrolyte (KOH) and leaves the cell (producing water)

Question 31

What is the ion exchange membrane?

Answer 31

So that the molecules don’t mix instead they go up to the wire to create a potential difference..

Question 32

What is the over all reaction for a fuel cell?

Answer 32

2H2 + O2 = 2H2O