Topic 3: Redox I

Question 1

What is an oxidation number?

Answer 1

The number of electrons which must be added or removed to become neutral

Question 2

What is the priority of oxidation number rules?

Answer 2

1. F always -1
2. H = +1
3. O = -2

This does not apply to the elements alone or in molecule form, i.e. F_2

Question 3

Oxidation

Answer 3

Loss of electrons

Question 4

Reduction

Answer 4

Gain of electrons

Question 5

Disproportionation reaction

Answer 5

When a single element in a single species is both oxidised and reduced simultaneously

reverse disproportionation =/= disproportionation

Question 6

What is the order of steps in balancing half equations in acidic solution?

Answer 6

1. Balance atoms (not H or O)
2. Balance O by adding H2O
3. Balance H by adding H+
4. Balance charge by adding electrons

Question 7

What is the order of steps to balance half equations in alkaline solutions?

I have no idea if we are supposed to know this

Answer 7

1. Balance like you would in acidic
2. Add OH- to both sides to make all the H+ water

Question 8

Reaction: chlorine + cold dilute NaOH

Answer 8

Cl2 + 2NaOH -> NaOCl + H2O + NaCl

sodium chlorate (I) is bleach

Question 9

Reaction: chlorine + hot concentrated NaOH

Answer 9

3Cl2 + 6NaOH -> NaClO3 + 5NaCl + 3H2O

sodium chlorate (V) is weedkiller