reactivity of metals & electrolysis

Oxidation

Loss of electrons, gains oxygen

Reduction

gain of electrons, loses oxygen

reactivity of metals

when metals react, they lose electrons, they are oxidised

transition metals

can lose different no. of electrons to form ions with different charges

Reactivity trend in alkali metals with water

More reactive down the group. Atoms have more shells, outer electron further away from nucleus so less attraction, electron lost easily.

Reactions of metals with oxygen; order of reactivity

Highest: potassium, sodium, lithium, calcium, magnesium, aluminium, carbon

metal + oxygen -->

metal oxide

Reactivity of metals with water; order of reactivity

Highest: potassium, sodium, lithium, calcium, magnesium, zinc, iron, copper

metal + water -->

metal hydroxide + hydrogen

Reactivity of metals with acid; order of reactivity

Highest: magnesium, zinc, iron, copper(no reaction)

What is an ore?

a naturally occurring substance containing metal/metal compounds

Iron ore

haematite

Aluminium ore

Bauxite

Extraction of metal

The more reactive the metal, more extreme method of extraction

Method of extraction for K, Na, Ca, Mg and Al

Electrolysis; uses alot of energy & expensive

Method of extraction for Z, Fe, Tin, Lead, H, Co

Heating metal oxide with carbon

Method of extraction for Sliver

Heating/smelting

Method of extraction for Gold & Platinum

Unreactive, doesn't need extracting

Displacement reactions of metals

More reactive element displaces less reactive element from a compound

Oxidation half equation

Mg -> Mg2+ + 2e-

Reduction half equation

Zn2+ + 2e- -> 2e-

Metals less reactive than carbon

Metals less reactive than carbon extracted by displacement with carbon

Reaction between copper oxide and carbon

Carbon become oxidised and copper is then reduced as carbon has displaced copper bc copper is less reactive than carbon

Ionic compounds

Held together by ionic bonds which are the electrostatic attraction between oppositely charged ions

Electrolysis

Breaking up of an ionic compounds using electricity

Why do ionic compounds not conduct electricity?

Ions can't move. Solid, ionic compounds can't be electrolysed.

To be an electrolyte

Must be molten or dissolved in water

Electrolysis set up

Anode, Cathode, Electrolyte solution, anions, cathions

Anode

Positive electrode, attracts anions (negative ions)

Cathode

Negative electrode, attracts cathions (positive ions)

The electrolyte solution

is the solution that is decomposed/broken up by passing electricity through it

At the CATHODE

positive ions gain electrons = electrons originally lost. Reduction as electrons are gained

At the ANODE

negative ions lose electrons = electrons originally gained. Oxidation as electrons are lost

Electrolysis of molten ionic compounds

When an ionic compound is electrolysed as molten, the metal is produced at the cathode, and nonmetal produced at the anode.

What ions are present in an aqueous solution of ionic compounds?

H+ and OH- ions, as well as metal and nonmetal ions.

What happens to positive and negative ions during electrolysis?

Both types of ions are attracted to the electrode, but only one is produced and one stays in solution.

What determines which ion is produced during electrolysis?

The reactivity of the ions.

Why is aluminium oxide dissolved in molten cryolite before electrolysis?

Aluminium oxide has a very high mp (2050 C), to save energy, they mix it with molten cryolite

How and where is copper extracted?

Extracted from high grade ores by electrolysis or displacement reactions

Phytomining

Plants grown in soil containing low grade copper ore, copper compounds absorbed through roots. Plants harvested/burned as fuel. Ash has copper compounds and is extracted by electrolysis/displacement.

Reasons why copper is extracted from low grade ores

High grade ores running out. New extraction methods use less energy

Bioleaching

Bacteria feed on low grade copper ores, absorb copper compounds & grown in them to produce leachate

Advantages of bioleaching & phytomining

Less energy- able to extract from low grade ores, no mining.

Phytomining plants used as fuel

Disadvantages of bioleaching & phytomining

Slower batch process, may not produce copper when needed, takes up land, energy still needed