What is oxidation?
Loss of electrons, gain of oxygen
What is reduction?
gain of electrons, loss of oxygen
metals reactivity series in order of most reactivity to least
potassium, sodium, lithium, calcium, magnesium, zinc, iron, copper
Which non-metals are often put into the reactivity series?
hydrogen and carbon
A more reactive metal will...
Displace a less reactive metal from its compound
ACRONYM for reactivity series
Please Stop Calling Me A Cute Zebra I Like Hearing Copper Silver Gold
most metals are found as
compounds that require chemical reactions to extract the metal
Metals less reactive than carbon
Can be extracted from their oxides by reduction with carbon
acids react with metals to produce
salt and hydrogen gas
What is a redox reaction?
an oxidation reaction paired with a reduction reaction
example of redox reaction
rusting
Acids and Bases
neutralize each other
Acid + Base
salt + water
Acid + metal carbonate
salt + water + carbon dioxide
How can soluble salts be made?
by reacting acids with insoluble bases such as metal oxides, metal hydroxides and metal carbonates
a) React the excess acid with some insoluble chemical (e.g. metal oxide) b) Filter off the leftovers c) Crystallise the product
strong acid
an acid that ionizes completely in aqueous solution (HCl)
weak acid
an acid that is only slightly ionized in aqueous solution (citric acid ethanoic acid)
What is an electrolyte?
a liquid containing free-moving ions which conducts electricity
what is electrolysis
The breaking down of a substance using electricity
positively charged ion
cation moves to negative electrode (cathode)
negatively charged ions move to
anion moves to anode (positive electrode)
what is an electrode
A solid that conducts electricity and is submerged in the electrolyte
When a simple ionic compound is electrolysed in the molten state using inert electrodes...
the metal is produced at the cathode and the non metal is at the anode
When is electrolysis used to extract metals
When the metal is more reactive than carbon OR if the metal reacts with carbon
Why must the anode be replaced regularly?
The anode must be replaced regularly because the oxygen produced at the anode reacts with the carbon in the graphite forming carbon dioxide gas
where is aluminium oxide found
bauxite
why is aluminium oxide hard to extract
because it has a high melting point and is found in bauxite
how can we prepare aluminium oxide for electrolysis
1- purify it 2- to make the ions free we need to make it molten so we mix it with cryolite which lowers the melting point
outcome of aluminium oxide electrolysis
negative oxygen ions move to the anode aluminium ions stay in the solution and can be extracted
rules for electrolysis of aqueous solutions at the cathode
•if it’s a metal more reactive than hydrogen then hydrogen is discharged •if it’s less reactive than hydrogen (eg copper) that will be discharged
rules for electrolysis at the anode
if it’s a halide (eg chloride, bromide, oxide) then it is discharged if it’s not a halide then hydroxide ions are discharged
what 2 ions are present in water
hydrogen and hydroxide
what is an aqueous solution
An aqueous solution is water that contains one or more dissolved substance eg salt water (nacl)
what is an ore
An ore is a rock that contains enough of a metal or a metal compound to make extracting the metal worthwhile
what do ionic equations show
the particles that change
what do half equations shiw
individual loss or gain of electrons for each atom
State the general equation for a neutralisation reaction in a short, ionic form.
H+ + OH- ———> H2O
As the pH is decreased by one unit, what change is seen in the hydrogen ion concentration?
increased by factor 10
What occurs at the cathode and what occurs at the anode during electrolysis?
reduction at cathode
oxidation and anode
In aqueous electrolysis, which element is discharged at the cathode? Oxygen is produced at the anode unless what?
The less reactive element discharges at the cathode. Hydrogen is produced unless there is a less reactive metal, in which case the said metal is produced. Oxygen is produced at the anode unless the solution contains halide ions, in which case halogen molecules are produced