3.1.7 Oxidation, Reduction, and Redox Reactions Knowledge

Question 1

what is oxidation in terms of transfer of electrons?

Answer 1

the loss of electrons

Question 2

what happens to the oxidation state, when a species is oxidised?

Answer 2

increases - number becomes more positive

Question 3

what is reduction in terms of transfer of electrons?

Answer 3

the gain of electrons

Question 4

what happens to the oxidation state, when a species is reduced?

Answer 4

decreases - number becomes more negative

Question 5

what is a redox reaction?

Answer 5

reaction where oxidation and reduction take place at the same time

Question 6

what is a reducing agent in terms of transfer of electrons?

Answer 6

• electron donor
• a reducing agent is itself oxidised

Question 7

what is an oxidising agent in terms of transfer of electrons?

Answer 7

• electron acceptor
• an oxidising agent is itself reduced

Question 8

what are oxidation states used for?

Answer 8

to follow the movement of electrons in redox reactions; to identify which substances have been oxidised and reduced

Question 9

is the charge or number given first in oxidation states?

Answer 9

charge

Question 10

what oxidation state do uncombined elements have?

Answer 10

0

Question 11

what is the sum of all oxidation states in a compound?

Answer 11

0

Question 12

what is the oxidation state of a simple ion equal to?

Answer 12

its charge

Question 13

what is the sum of all oxidation states in a complex ion equal to?

Answer 13

its charge

Question 14

what is the oxidation state(s) of hydrogen?

Answer 14

• usually +1
• in metal hydrides (e.g. LiH) -1

Question 15

what is the oxidation state(s) of group 1 metals?

Answer 15

+1

Question 16

what is the oxidation state(s) of group 2 metals?

Answer 16

+2

Question 17

what is the oxidation state(s) of aluminium?

Answer 17

+3

Question 18

what is the oxidation state(s) of oxygen?

Answer 18

• usually -2
• in peroxides (e.g. Na2O2), -1
• when reacted with fluorine (OF2), +2

Question 19

what is the oxidation state(s) of fluorine?

Answer 19

-1

Question 20

what is the oxidation state(s) of chlorine?

Answer 20

• usually -1
• is positive if reacted with oxygen or fluorine

Question 21

what is the oxidation state(s) of bromine?

Answer 21

• usually -1
• is positive if reacted with oxygen or fluorine

Question 22

what is the oxidation state(s) of iodine?

Answer 22

• usually -1
• is positive if reacted with oxygen or fluorine

Question 23

why is the oxidation state of fluorine always -1?

Answer 23

it is the most electronegative element; no other element can remove an electron from fluorine

Question 24

in what order are oxidation states assigned?

Answer 24

• Uncombined elements (0)
• Metals (G1, G2, Al)
• Fluorine (-1)
• Hydrogen (+1)
• Oxygen (-2)
• Chlorine (-1)

Question 25

how do you balance a simple half-equation?

Answer 25

with e-

Question 26

what are the rules for balancing complicated half-equations?

Answer 26

1. balance the main atom (not H or O)
2. Balance O using H2O
3. Balance H using H+
4. Balance charge using e-

Question 27

what are the steps for combining half-equations?

Answer 27

1. multiply one or both half-equations until they both contain the same no. electrons
2. add the reactants from both half-equations together
3. add the products from both half-equations together
4. cancel out the electrons

Question 28

what is a disproportionation reaction?

Answer 28

a reaction in which one type of atom is both oxidised and reduced

Question 29

what is oxidation in terms of oxygen transfer?

Answer 29

gain of oxygen

Question 30

what is reduction in terms of oxygen transfer?

Answer 30

loss of oxygen

Question 31

what is an oxidising agent in terms of oxygen transfer?

Answer 31

substance which gives oxygen to another substance

Question 32

what is an reducing agent in terms of oxygen transfer?

Answer 32

substance which removes oxygen from another substance.

Question 33

what is oxidation in terms of hydrogen transfer?

Answer 33

loss of hydrogen

Question 34

what is reduction in terms of hydrogen transfer?

Answer 34

gain of hydrogen

Question 35

what is an oxidising agent in terms of hydrogen transfer?

Answer 35

oxidising agents remove hydrogen from another substance

Question 36

what is an reducing agent in terms of hydrogen transfer?

Answer 36

reducing agents give hydrogen to another substance