Redox Reactions

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1

Slide 1

Redox Reactions.

Oxidation

Reduction

Slide 2

GCSE

Oxidation:

Gain of oxygen

Loss of electrons

Reduction:

Loss of oxygen

Gain of electrons

Increase in

oxidation

number

Decrease in

oxidation

number

Slide 3

4 Experiments:

Burning magnesium

Copper in silver nitrate solution

Chlorine solution and potassium iodide solution

Exploding hydrogen

Word equation

Balanced symbol equation

Slide 4

2Mg(s) + O2(g)  2MgO(s)

Oxidised – gains oxygen

Must be a redox!

Mg  Mg2+

O  O2-

Put the

e- in.

+2e-

+2e-

Oxidised – loss of e-

Reduced – gain of e-

Slide 5

Cu(s) + 2AgNO3(aq)  Cu(NO3 )2(aq) + 2Ag(s)

Ag+  Ag

Cu  Cu2+

Complete the half-equations

+e-

+2e-

Oxidised?

Reduced?

Oxidised – loss of e-

Reduced – gain of e-

Slide 6

Try Question 1.

Slide 7

H2(g) + ½ O2(g)  H2O(g)

Covalent!

No H+ or OH-

Need a new

definition.

Slide 8

GCSE

Oxidation:

Gain of oxygen

Loss of electrons

Reduction:

Loss of oxygen

Gain of electrons

Increase in

oxidation

number

Decrease in

oxidation

number

Slide 9

Oxidation Numbers

The oxidation number of an atom in an element is zero. E.g. Mg in Mg, O in O2.

Slide 10

Oxidation Numbers

The oxidation numbers of atoms in a compound add up to zero.

Oxidation state of C in CO2?

? – 4 = 0

? = +4

Put the +!

Slide 11

Oxidation Numbers

The oxidation numbers of atoms in a compound add up to zero.

Oxidation state of Mg in MgCl2?

+2

Slide 12

Oxidation Numbers

The oxidation numbers of atoms in a compound add up to zero.

Oxidation state of N in NH3?

-3

Slide 13