Redox Reactions

Question 1

Reduction and oxidation

Answer 1

Gain of electrons or decrease in oxidation number
Loss of electrons or increase in oxidation number

Question 2

Oxidising agent and reducing agent

Answer 2

OA: Takes electrons from the species being oxidised, oxidising agent contains the species that is reduced

RA: Adds electrons to the species being reduced. Reducing agents contain the species that is oxidised

Question 3

Hydrogen peroxide (H2O2) acting as reducing agent

Answer 3

H2O2 (aq) to O2(g)

H202 ( aq) —> O2 + 2H+(aq) + 2e-

Question 4

Hydrogen peroxide acting as oxidising agent ( in acidic conditions)

Answer 4

H2O2 to H2O

H2O2 (aq) + 2H+ + 2e- —> 2H2O(l)

Question 5

Hydrogen peroxide acting as oxidising agent ( in alkaline conditions )

Answer 5

H2O2 to OH-

H2O2 (aq) + 2e- —> 2OH- (aq)

Question 6

MnO4- to Mn2+ (colour change)

Answer 6

Purple (Mn 7+ ) to almost colorless ( Mn2+) but slightly pale pink because of excess of MnO4- (aq)

Question 7

MnO4- to…
Fe 2+ to…

Answer 7

MnO4- to Mn2 +
Fe 2+ to Fe 3+

Question 8

Special cases ONo.
H in metal hydrides
O in peroxides
O bonded to F

Answer 8

-1 e.g NaH,CaH2
-1
+2 e.g F2O

Question 9

Oxidation number of a species

Answer 9

Measure of the number of electrons that an atom uses to bind with atoms of another element