Oxidation-Reduction

Define oxidation in terms of electron transfer

Loss of electrons

Define reduction in terms of electron transfer

Gain of electrons

What is an oxidising agent

causes oxidation

What is a reducing agent

Causes reduction

What is corrosion

Metal is converted into its compounds

How can corrosion of metals/rusting be prevented

1. Oiling, greasing or painting

2. Electroplating

3. Galvanising

4. Using sacrificial anodes

What is combustion

Burning of a substance in oxygen

What is Respiration

Release of energy from glucose in cells

Define oxidation number

Charge an atom has or appears to have when electrons are distributed according to rules

Define oxidation in terms of change in oxidation number

Increase in oxidation number

Define reduction in terms of change in oxidation number

Decrease in oxidation number

What is the electrochemical series

All metals are oxidised when they react.

Electrochemical series is a table of metals arranged in order of how easily they lose electrons.

Higher up the metal, the more easily it will reduce other substances.

Higher end of electrochemical series

Lithium (Li)

Potassium (K)

Calcium (Ca)

Sodium (Na)

Magnesium (Mg)

Aluminium (Al)

Middle end of electrochemical series

Zinc (Zn)

Iron (Fe)

Lead (Pb)

Hydrogen (H)

Lower end of electrochemical series

Copper (Cu)

Mercury (Hg)

Silver (Ag)

Gold (Au)

zinc metal with copper (II) sulfate solution procedure

1. Make copper (ii) sulfate solution

2. Place zinc into solution

zinc metal with copper (II) sulfate solution results

Blue color becomes colorless

Copper displaced out of solution as a brown/red metal.

Exception in Oxygen (H2O2)

Hydrogen is +1, for the sum to add to 0, oxygen is -1

magnesium metal with copper (II) sulfate solution procedure

1. Make a copper sulfate solution

2. Using tongs, lower magnesium ribbon into solution

magnesium metal with copper (II) sulfate solution result

Blue color becomes colourless

Copper displaced out of solution as a brown/red metal

Exception for oxygen (OF2)

Fluorine is more electronegative atom, it takes -1 for the sum to add to 0, oxygen is +2

Comment on the rate of this reaction compared to when zinc is added to copper (II) sulfate solution

Happens at faster rate

Magnesium is more places above copper in the electrochemical series than zinc is; magnesium displaces copper more quickly

Blue becoming colourless and formation of copper will occur more quickly.

copper metal with silver nitrate solution procedure

1. Make a silver nitrate solution

2. Place copper in solution

copper metal with silver nitrate solution results

Colorless becomes blue

Silver metal out of solution

Give an application of knowledge of the electrochemical series

Scrap iron used to displace copper from a compound

Copper is useful in electronics industry

Exception in hydrogen

In metal hydrides hydrogen =-1

Which metals from the electrochemical series are found free in nature? Explain.

Lead, copper, silver, gold

These are at the bottom of electrochemical series and won’t oxidise easily.