electrode potentials

Question 1

what’s a strip of metal dipped in a solution of its own ions called

Answer 1

electrode
or
half cell

Question 2

when a strip of metal is dipped in a solution of its own ions which has a postive charge and which has a negative charge

Answer 2

the ions dissolve in the solution giving it a positive charge
the electrons collect on the metal giving it a negative charge
this means a potential difference is established between the too

Question 3

if there is a large voltage where does the equilibrium lie

Answer 3

right

Question 4

how do you connect two half cells

Answer 4

the two metal rods connected by a high resistance voltmeter

the two beakers of electrolyte are connected with a salt bridge to complete the circuit

Question 5

why is pottasium nitrate a suitable solution for a salt bridge

Answer 5

it’s in reactive and the ions are free to move

Question 6

where will the electrodes try to flow to

Answer 6

from the most reactive metal (left electrode) to the least reactive metal (right electrode)

Question 7

what does a voltmeter do

Answer 7

prevents electrons flowing enabling a voltage to be measured

Question 8

what would happen if a voltmeter is replaced with an ammeter or a bulb

Answer 8

electrons can flow and a current is produced

Question 9

why might the current produced by a cell fall to zero after some time

Answer 9

all the reactants are used up

Question 10

what will happen to a cell once the reactants are used up

Answer 10

stops working or starts to leak

Question 11

when is a platinum electrode used

Answer 11

when there is no sold metal in the reaction
such as when there are metal ions of two difffent charged in the same solution
eg Fe2+ and Fe3+

in this case a metal rod made from another in unreactive metal is needed to connect the circuit so platinum is used

Question 12

why is platinum a suitable electrode

Answer 12

it’s unreactive and conducts electricity

Question 13

describe conditions of a standard electrode

Answer 13

H2 gas is pumped in at a pressure of 100kPa
the electrolyte contains H+ ions of concentration 1moldm^-3
platinum electrode
whole system at a temp of 298K

Question 14

what is the voltage of a standard hydrogen half cell

Answer 14

0

Question 15

all electrodes equations are shown as …..

Answer 15

reductions

Question 16

the standard electrode potential of cu^2+/Cu is 0.37V why might the electrode potential of the following cell not be 0.37v

Answer 16

the concentration of the CuSO4 solution is not 1 mol dm^-3

Question 17

what is being oxsidised and reduced in this convential cell representation

Answer 17

ROOR

Question 18

the right electrode is the ……… electrode

Answer 18

postive

Question 19

the right electrode has a more …….. standard electrode potential then the left electrode

Answer 19

postive

Question 20

the left electrode is the …….. electrode

Answer 20

negative

Question 21

what do vertical solid lines indicate in a convential cell representation

Answer 21

phase boundaries

Question 22

what does a double vertical line in the middle of a convential cell representation represent

Answer 22

salt bridge

Question 23

the species with the …….. oxidation state should be written closest to the salt bridge

Answer 23

highest

Question 24

draw the cell representation of the standard hydrogen half cell

Answer 24

Question 25

the standard hydrogen electrode is always written on the …..

Answer 25

left

Question 26

all the species on the left of the arrow are ……..

Answer 26

oxidising agents
as the can only gain electrons

Question 27

which is the most strongest oxidising agent

Answer 27

top left of the table with most positive standard electrode potential

Question 28

if the table is +ve
⬇️
-ve
then you can use sowr

Answer 28

strongest oxidising agent top left
weakest reducing agent top right

Question 29

equations for working out voltage of a cell

Answer 29

Ecell = more positive - least postive

Question 30

what does it mean if an E cell value is postive

Answer 30

reaction is feasible and the cell discharges - produces a current

Question 31

how do you recharge a cell

Answer 31

if a reaction is reversible you can charge it by plugging it in the mains and the reverse reaction will occur.

Question 32

give an environmental advantage of using rechargeable cells

Answer 32

metals are reused

Question 33

give an environmental disadvantage of using rechargeable cells

Answer 33

mains electricity is used to recharge which may come from combusting fossil fuels which realises CO2

Question 34

why are conditions important in Ecells

Answer 34

shift equilibrium changing electrode potentials affecting Ecell values
meaning some reactions are feasible under some conditions and not others

Question 35

in which direction would the electrons flow in this cell why ?

Answer 35

from right to left
the Cu2+ is more concentrated on the left so reduction on Cu2+ is more likely to happen on the left

the left electrode is the postive electrode so the right is the negative electrode

Question 36

what kind of reaction do single use batteries have in them

Answer 36

irreversible

Question 37

how do fuel cells create a voltage

Answer 37

uses energy from reaction of a fuel with oxygen to create a voltage

Question 38

how would you provide a constant voltage in a fuel cell

Answer 38

continuously provide fuel and oxidant

Question 39

what fuel do fuel cells use name 3

Answer 39

methanol
natural gas
petrol

Question 40

name advantages of using fuel cells for energy instead of fossils fuels

Answer 40

greater efficiency then burning hydrogen in a combustion engine

less polluting as water is the only product

Question 41

disadvantages of using fuel cells for energy instead of fossil fuels

Answer 41

H2 is difficult to store
fossil fuels are combusted to produce the hydrogen which releases carbon dioxide

Question 42

advantages of fuel cells compared to other types of cell

Answer 42

voltage is constant as fuel and oxygen is supplied constantly so concentrations of reactants remain constant