Oxidation and Reduction

Question 1

Oxidation in terms of oxygen

Answer 1

Gain

Question 2

Reduction in terms of oxygen

Answer 2

Lose

Question 3

Oxidation in terms of hydrogen

Answer 3

Lose

Question 4

Reduction in terms of hydrogen

Answer 4

Gain

Question 4

Oxidation in terms of electrons

Answer 4

Lose (OIL/LEO)

Question 5

Reduction in terms of electrons

Answer 5

Gain (RIG/GER)

Question 6

Oxidation in terms of oxidation state (charge)

Answer 6

Increase

Question 7

Reduction in terms of oxidation state (charge)

Answer 7

Decrease

Question 8

Oxidation Mnemonic OxGOLEH O.S up

Answer 8

Oxidation means Gain Oxygen, Lose Electrons and Hydrogen, Increase in Oxidation State.

Question 9

Reduction Mnemonic ReLOGEH OS down

Answer 9

Reductions is Lose Oxygen, Gain Electrons and Hydrogen, Decrease in Oxidation State.

Question 10

Redox Example: Mg + H2O → MgO + H2

Answer 10

Explanation 1:
Mg gains oxygen to form MgO while H2O loses oxygen to form H2. Thus Mg is oxidized to
MgO while H2O is reduced to H2.

Explanation 2:
Oxidation state of Mg increases from 0 in Mg to +2 in MgO while oxidation state of H
decreases from +1 in H2O to 0 in H2. Thus, Mg is oxidized to MgO while H2O is reduced to
H2.

Question 11

What is an oxidising agent?

Answer 11

An oxidizing agent causes oxidation, it is the substance reduced in a reaction.

Question 12

What is a reducing agent?

Answer 12

A reducing agent causes reduction, it is the substance oxidized in a reaction.

Question 13

Test for OA

Answer 13

Add aqueous potassium iodide, KI. KI is a reducing agent.

Question 14

If OA is present, what would be the positive test observation?

Answer 14

A brown solution of iodine is formed.

Question 15

What is the test for Reducing Agent?

Answer 15

Add acidified potassium
manganate (VII), KMnO4.
KMnO4 is an oxidizing agent.

Question 16

If RA is present. what is the positive test observation?

Answer 16

Acidified potassium
manganate(VII) solution
changes from purple to
colourless.

Question 17

Zn + 2HCl → ZnCl2 + H2

State the change of
oxidation state of Zn in
the above reaction

Answer 17

The oxidation state of Zn
increases from 0 in Zn to +2 in ZnCl2.

Question 18

Describe, in terms of
electrons whether
oxidation or reduction
has occurred.

Zn → Zn2+

Answer 18

Zn loses two electrons to formZn2+. Hence oxidation occurs.

Question 19

Zn + 2HCl -> ZnCl2 + H2

Identify the oxidizing
agent. Explain.

Answer 19

Zn undergoes oxidation when the oxidation state of Zn increases from 0 in Zn to +2 in ZnCl2.

Hence, HCl is the oxidizing agent that causes Zn to be oxidized.

Question 20

Describe what is
observed when acidified
potassium manganate
(VII) is added to a
reducing agent.

Answer 20

The acidified potassium
manganate (VII) turns from purple to colourless.

Or

The purple acidified potassium manganate (VII) decolourises.