P- Oxidation & Reduction

Question 1

What is oxidation?

Answer 1

• gain in O2
• loss of e- (+ e- on RHS)
  :)
• loss of H2
• ↑ oxidation no. (eg. Mg–>Mg2+ - 0–> +2)

Question 2

What is reduction?

Answer 2

• loss of O2
• gain in e- (+e- on LHS)

:)
- gain in H2
- ↓ oxidation no. (eg. O2–>O2- : 0–> -2)

Question 3

Oxidising agent def

Answer 3

e- acceptor

Question 4

Reducing agents def

Answer 4

e- donor

Question 5

Oxidation state of oxygen in compounds
(w/ special cases)

Answer 5

-2
- peroxides: -1 (1 mole of the element per O)
- fluoride (OF2): +2

Question 6

Oxidation states of hydrogen in compounds
(w/ special cases)

Answer 6

+1
- ionic hydrides (w/ group1 + 2): -1

Question 7

Why is oxidation state of fluorine always -1?

Answer 7

most electronegative element

Question 8

Oxidation states of halogens

Answer 8

-1
- except for when w/ F (eg. ClF3 {Cl:+3})

Question 9

What happens to the oxidation number in reduction?

Answer 9

decreases

Question 10

Name of HNO3

Answer 10

• N: +5
• Nitric (V) acid

Question 11

Name of KMnO4

Answer 11

KMnO4
- Mn: +6
- potassium mangenate* (VII)*
- only for elements w/ varying oxidation states

Question 12

Name of Na2Cr2O7

Answer 12

Na2Cr2 O7
- sodium dichromate (VI)
- only for elements w/ varying oxidation states

Question 13

What does the following equation show?
2MnO4- + 16H+ + 10Cl- –> 2Mn2+ + 8H2O + 5Cl2

Answer in 3 parts

Answer 13

1. reduction of Mn(VII) to Mn(II)
2. by Cl-
3. in the presence of acid

Question 14

Steps to constructing a complex half equation

Answer 14

1. balance atoms undergoing redox
2. balance O atoms by + H2O
3. balance H atoms by + H+ ions
4. balance charges by + e-

check no. of atoms & charges are balanced + cancel out any H2O on both sides