Redox

What is reduction in terms of oxygen, electrons and hydrogen?

Loss of oxygen

Gain of electrons

Gain of hydrogen

What is oxidation in terms of oxygen, electrons and hydrogen?

Gain of oxygen

Loss of electrons

Loss of hydrogen

What’s an oxidation state?

The number of electrons something needs to gain or lose to become neutral

What is the oxidation number of an uncombined element? Eg C, H, O2

0

What is the oxidation number on a single ion?

The charge on the ion

Whats the oxidation state for a group 1 element?

Always +1

Whats the oxidation state for a group 2 element?

Always +2

Whats the oxidation state for a group 3 element?

Always +3

Whats the oxidation state for hydrogen?

+1

Except in hydrides where it is -1

Whats the oxidation state in chlorine?

-1

Except if in a compound with F and O - it would have a positive value

Whats the oxidation state in fluorine?

Always -1

Whats the oxidation state in oxygen?

-2

Except in peroxides where it is -1 or in OF2 where it is +2

When an element has more than one stable oxidation number, how is it indicated?

Using Roman numerals (stock notation)

How do oxidation states relate to overall charge?

Sum of oxidation states = overall charge

What is a redox reaction?

A reaction in which reduction and oxidation both take place

How do you write half equations? (5)

1. Write what you know as an equation

2. Balance for atoms (not O or H)

3. Balance for O by adding H2O

4. Balance for H by adding H+ ions

5. Balance charge by adding e-

What is a reducing agent and what does it do?

Causes something else to be reduced

Donates (loses) electrons

Gets oxidised

What is an oxidising agent and what does it do?

Causes something else to be oxidised

Accepts (gains) electrons

Gets reduced

What happens to a species oxidation number if it is reduced?

It decreases

What happens to a species oxidation number if it is oxidised?

It increases

Define disproportionation

Where in a redox reaction, a single element is oxidised and reduced simultaneously, forming 2 different products