Redox Reaction

Question 1

what is a redox reaction?

Answer 1

type of chemical reaction which involves transfer of electrons between two chemical species

Question 2

State the oxidation rules for the following

atom in free uncombined state _______
sum of the oxidation numbers of all the atoms or ions in a compound_____
oxidation number of a monoatomic ion in an ionic compound___________
oxidation number of hydrogen in a compound or polyatomic ion is (a)_____________ except in hydrides where it is (b)______________
oxidation number of oxygen in a compound or polyatomic ion is (a)_____________ , except in peroxides where it is (b)______________
the sum of the oxidation numbers of the atoms in a plyatomic ion is____________
the elements in covalent compounds or polyatomic ions (a)______________ except (b)______________ and (c) __________

Answer 2

0
0
same as the charge on the ion
(a) +1 , (b) -1
(a) -2, (b) -1
the same as the charge on the ion
(a)may vary, (b) hydrogen, (c) oxygen

Question 3

an oxidising agent causes the oxidation number of an element in free or combined state to (1)__________ by causing it to (2)__________ electrons. the oxidising agent itself is (3)___________ because it (4) ___________ electrons in the process.

Answer 3

increase
lose
reduced
gains

Question 4

a reducing agent causes the oxidation number of an element in free or combined state to (1)__________ by causing it to (2)__________ electrons. the reducing agent itself is (3)___________ because it (4) ___________ electrons in the process.

Answer 4

decrease
gain
oxidised
loses

Question 5

examples of oxidising agents

Answer 5

potassium iodide solution
Iron sulfate

Question 6

Oxidation(in terms of electrons)

Answer 6

the loss fo electrons by an element in its free state or a element in a compund

Question 7

Reduction(in terms of electrons)

Answer 7

the gain of electrons by an element by in its free state or in a compound

Question 8

examples of reducing agent

Answer 8

Acidified Potassium Manganate solution
Acified potassium dichromate solution

Question 9

Visble Colour Change Observed
Potassium Iodide solution(Kl)(FeS04)

Answer 9

Colourless to brown

Question 10

Visble Colour Change Observed
Iron sulfate solution(FeS04)

Answer 10

Pale green to yellow brown

Question 11

Visble Colour Change Observed
Acidified Potassium Manganate solution

Answer 11

Purple to colourless

Question 12

Visible Colour Change Observed
Acidified potassium dichromate solution

Answer 12

Orange to Green

Question 13

What substance is reduced in this reaction?

C₂H₄(g) + 3 O₂(g) → 2 CO₂(g) + 2 H₂O(g)
Ca(s) + H₂SO₄(aq) → CaSO₄(aq) + H₂(g)

Answer 13

Oxygen
H2SO4(aq)

Question 14

what substance is oxidised and what is the oxidising agent in the reactions below?

Ca(s) + H₂SO₄(aq) → CaSO₄(aq) + H₂(g)
Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g)

Answer 14

Ca is oxidized by H₂SO₄(aq)
Zn(s) is oxidised by H₂SO₄(aq)

Question 15

To determine if a substance is a reducing agent add it to a known (1) ______________ , most commonly (2)_________________ or 3) __________________

Answer 15

Oxidizing agent 2. Acidified potassium manganate(VII) 3. Acidified potassium dichromate(VI)

Question 16

To determine if a substance is an oxidizing agent add it to a known (1) ______________ , most commonly (2)_________________ or 3) __________________

Answer 16

Reducing agent 2. Potassium iodide solution 3. Aqueous solution of iron(III) salt

Question 17

how do redox reactions account for rusting?

Answer 17

moisture and oxygen react with iron and its alloy steel causing the iron to be oxidized to form hydrated iron(III) oxide (Fe2O3.xH2O)

Question 18

chlorine bleaches contain (1)_____________ and oxygen bleaches contain (2)_____________ which are both (3)_____________ and will remove coloured stains by oxidising the coloured dyes to thier colourless forms.

Answer 18

sodium chlorate(I) (NaClO)
H2O2
Oxidising agents

Question 19

explain the browning of fruits and vegetables when they are cut

Answer 19

enzymes in the cells on the cut surfaces of the fruit or vegetable use the oxygen in the air to oxidise certain chemicals in the cells to brown compounds called melanins

Question 20

Oxidation(in terms of oxidation number)

Answer 20

Oxidation is the increase in the oxidation number of an element in it free state or inan compund

Question 21

Reduction( In terms of oxidation number)

Answer 21

Reduction is the decrease in the oxidation number of an element in its free state or an element in a compound

Question 22

Substances that can behave as both oxidising aand reducing agent

Answer 22

Sulfer dioxide
Acidified hydrogen peroxide