Chemistry - Oxidation and Reduction

What are oxidation-reduction reactions also known as ?

redox reactions

What is oxidation ?

The loss of electrons

What is reduction ?

The gain of electrons

What does an oxidising agent do ?

Cause another substance to be oxidised

It does this by gaining those electrons itself, therefore an oxidising agent is always reduced

What does a reducing agent do ?

Causes another substance to be reduced

It does this by donating those electrons, therefore a reducing agent is always oxidised

When does corrosion occur ?

When a metal is oxidised

How is corrosion prevented ?

Oiling, greasing, electroplating or painting the metals

What is electroplating ?

Covering a metal with a thin layer of another metal

What are combustion reactions often called ?

Burning

Why is respiration a redox reaction ?

There is a transfer of electrons from carbon to oxygen

What is an oxidation number ?

That charge that an atom has or appears to have when electrons are distributed under certain rules

What is oxidation ? (in terms of oxidation numbers)

an increase in oxidation number

What is reduction ? (in terms of oxidation numbers)

a decrease in oxidation number

What are the rules for assigning oxidation numbers ?

Each atom in a pure element has an oxidation number of 0

The oxidation number of simple ion equals its charge

The sum of the oxidation numbers of all atoms in a neutral compound must equal 0

The sum of oxidation numbers in a polyatomic ion must equal the charge of the polyatomic ion

What are the rules for assigning oxidation numbers ?(2)

In compounds, oxygen has an oxidation number of -2 except in OF₂ and peroxides

In compounds, hydrogen has an oxidation number of +1 except in metal hydrides

In compounds, the halogens usually have an oxidation number of -1 unless bonded to a more electronegative atom

In compounds, elements in group 1 have an oxidation number of +1, and elements in group 2 have an oxidation number of +2

What is the oxidation number of oxygen in peroxides ?

-1

What is the oxidation number for oxygen in OF₂ ?

+2 (F is more electronegative than O and will force O to lose electrons rather than gain)

How is a metal hydride formed ?

When hydrogen bonds to a metal