5.2.3 Redox and electrode potentials

Question 1

reduction

Answer 1

gain of electrons

Question 2

oxidation

Answer 2

loss of electrons
increase in oxidation numbers

Question 3

oxidation number of uncombined element

Answer 3

0

Question 4

oxidation number of combined hydrogen

Answer 4

+1

Question 5

oxidation number of combined oxygen

Answer 5

-2

Question 6

oxidation number of ion of element

Answer 6

ionic charge

Question 7

oxidising agent

Answer 7

takes electrons from species being oxidised
contains species being reduced

Question 8

reducing agent

Answer 8

adds electrons to species being reduced
contains species being oxidised

Question 9

what is a half cell

Answer 9

contains chemical species present in a redox half equation

Question 10

voltic cell

Answer 10

made by connecting 2 different half cells to allow electrons to flow

Question 11

isolated half cell

Answer 11

no net transfer of electrons either into or out of the metal

Question 12

what determines the direction of flow of electrons when 2 half cells are connected

Answer 12

depends on the relative tendency of each electrode to release electrons

Question 13

ion half cell

Answer 13

contains ions of the same element in different oxidation states
- there’s no metal to transport electrons either into or out of the half cell so inert metal electrode made out of platinium is used

Question 14

electrode potentials of a cell eith 2 metals or metal ion half cells connected

Answer 14

more reactive metal releases electrons more readily and is oxidised

Question 15

electrode potentials in an operating cell

Answer 15

electrode with more reactive metal loses electrons and is oxidised - the negative electrode

electrode with less reactive metal gains electrons and is reduced - positive electrode

Question 16

standard electrode potential

Answer 16

tendency to be reduced and gain electrons

Question 17

standard conditions used for electrode potential

Answer 17

1 mol dm-3
298K
100kPa (1 atm)

Question 18

standard electrode potential of a standard hydrogen electrode

Answer 18

exactly 0V

Question 19

measuring standard electrode potential

Answer 19

2 electrodes connected by wire to allow controlled flow of electrons
2 solutions connected with salt bridge to allow ions to flow

Question 20

the more negative the standard electrode potential(E)

Answer 20

greater tendency to lose electrons and undergo oxidation
less tendency to gain electrons and undergo reduction

Question 21

more positive the standard electrode potential (E)

Answer 21

greater tendency to gain electrons and undergo reduction

Question 22

do metals or non metals tend to have a more positive standard electrode potential

Answer 22

non metals

Question 23

the more negative the standard electrode potential

Answer 23

greater reactivity of a metal in losing electrons

Question 24

the more positive the standard electrode potential

Answer 24

greater reactivity of a non-metal in gaining electrons

Question 25

standard cell potential equation

Answer 25

E(positive electrode) - E(negative electrode)

Question 26

how to cobine half equations to make overall equation

Answer 26

redox system with less negative E value will react left to right and gain electrons - reduction
redox system with more negative E value will react right to left and lose electrons - oxidation

Question 27

give 2 limitations of predictions of feasibility from electrode potentials

Answer 27

reaction may not take place because activation energy is to high
reactions may not take place with 1 mol dm-3 solutions

Question 28

how are 2 half cells connected to make a cell

Answer 28

wires with voltmeter between electrodes
salt bridge between the solutions

Question 29

what is a salt bridge

Answer 29

concentrated solution of an electrolyte soaked into filter paper to connect 2 half cells

Question 30

which electrode is used to measure standard electrode potentials of other half cells

Answer 30

standard hydrogen electrode