4.3 oxidation and redox

Question 1

OXIDATION

Answer 1

is the process of losing electrons (OIL)

Question 2

REDUCTION

Answer 2

is the process of gaining electrons (RIG)

Question 3

REDOX

Answer 3

reaction is a reaction, which involves reduction and oxidation occurring. It involves
a transfer of electrons. Reduction and oxidation must ALWAYS occur together.

Question 4

OXIDISING AGENT

Answer 4

brings about oxidation but is itself reduced – it is an acceptor of
electronsbrings about oxidation but is itself reduced – it is an acceptor of
electrons

Question 5

REDUCING AGENT

Answer 5

brings about reduction but is itself oxidised – it is a donor of
electrons.

Question 6

OXIDATION NUMBER

Answer 6

is the number assigned to an atom or ion to describe its relative
state of oxidation or reduction

Question 7

DISPROPORTIONATION

Answer 7

reaction occurs when the same element is both oxidised and
reduced in a reaction

Question 8

what are the 10 oxidation rules

Answer 8

Uncombined elements have an oxidation state of 0
e.g. Mg, S, Cl2, O2, H2

Group I elements when combined have an oxidation number of +1

Group II elements when combined have an oxidation number of +2

In neutral molecules the sum of the oxidation numbers is 0
e.g. CO2 → +4 from C, (-2 x 2) from 2 O = 0 overall charge

In ions, the sum of the oxidation numbers equals the charge on the ion
e.g. [OH]- → -2 from O, +1 from H = -1 overall charge

Hydrogen has an oxidation number of +1 in all compounds except a metal hydride
where it is -1 (e.g. Na+H-) – this will be specified if it is the case.

Oxygen has an oxidation number of -2 in all compounds except peroxides (O22-)
e.g. hydrogen peroxide, oxygen has an oxidation number of +1, and OF2 where
oxygen oxidation number is +2.

In any substance the more electronegative element has the negative oxidation number
and the less electronegative element has the positive oxidation
e.g. fluorine is more electronegative than oxygen 🡪 so in OF2, oxygen is +2, and
fluorine is -1

Chlorine always has a negative oxidation number unless bound to O or F, then it will be
positive.

In any substance the more electronegative element has the negative oxidation
number and the less electronegative element has the positive oxidation e.g. fluorine is more electronegative than oxygen 🡪 so in OF2, oxygen is +2, and
fluorine is -1

Question 9

oxidation state rules - special cases with examples

Answer 9

fluorine compounds F takes -1 priority
oxygen is always 2- unless peroxides (-1)eg. na202, h202 or 02 0 or bonded to F oxygen takes on +2
Hydrogen +1 except when metal hydrides -H eg. NaH CaH2

Question 10

the oxidation number for elements is always 0

Answer 10

H2, O2, P4, S8, Na Fe all 0

Question 11

the sign of the oxidation number always comes ….. after the number

Answer 11

BEFORE

Question 12

sytematic name is given in ….. format

Answer 12

roman numeral eg. Iron (II)

Question 13

the more electronegative element always takes the …… oxidation number

Answer 13

negative eg cl- becomes positive when bonded to more electronegative o or f