C4 - Chemical Changes Flashcards
What is a displacement reaction
When a more reactive metal displaces a less reactive metal from a compound
Metal + Acid ——>
Salt + Hydrogen
Metal carbonate + acid —->
Salt +Carbon dioxide + water
Group 1 metals are ____reactive than hydrogen, so _____ it to produce hydrogen gas and a metal ______
More, displace , hydroxide
What happens in a blast furnace?
Iron oxide is reduced to form iron via a displacement reaction
We can use displacement reactions to
Obtain metals from their ores
Order of the reactivity series
Potassium
Sodium
Lithium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Tin
Lead
Hydrogen
Copper
Silver
Gold
Platinum
OIL RIG stands for
Oxidation is loss (of electrons)
Reduction is gain (of electrons)
What is neutral on the pH scale?
7
What is more acidic on the pH scale
Below 7
What is more alkaline on the pH scale
More than 7
Why does an acid of a low pH
It is due to its H+ ions
Why does an alkaline have a pH above 7
Due to its OH- ions
pH is dependent on the concentration of
H+ or OH- ions
A change of 1 pH is a ____ change of concentration of ___ or ____ ions
10x change in concentration of H+ or OH- ions
pH also depends on how _____/______ an acid is
Strong/weak
A strong acid will __________ more completely than a weak acid
Dissociate
3 examples of strong acids
Hydrochloric
Sulphuric
Nitric
3 examples of weak acids
Ethanoic
Citric
Carbonic
What do we use to measure what volume of acid/alkali is needed to neutralise
Burette
Method of titration
-Measure 50cm3 of alkali of known concentration using a glass pipette and put it in a conical flask with PHENOLPHTHALEIN indicator
-Place flask on a white tile underneath the tap of burette
—Put acid of unknown concentration in burette (up to 0cm3 mark), open the tap and let it drip into flask
—Once the solution in the flask turns pink, stop and swirl the concicql flask
-If it goes colourless then neutralisation has occurred
-use moles to calculate the unknown concentration of the acid
-
Define electrolysis
Passing an electrical current through a substance to cause oxidation and reduction at two electrodes
What happens at the anode
Oxidation
What happens at the cathode
Reduction
Electrolysis can only happen if ions are
Free to move to the electrode that they are attracted to
Why can’t electrolysis take place for solids
Ions are not free to move
During electrolysis of molten aluminium oxide why does the graphite anode need to be replaced regularly
Oxygen reacts with the carbon in the graphite anode to create carbon dioxide gas
Why do we use cryolite during electrolysis of molten aluminium oxide
Lowers the boiling point of aluminium oxide, so it is cheaper
During electrolysis of molten aluminium oxide, O2- ions are attracted to the ______ and are oxidised to form O2
Anode
Half equation at the anode during electrolysis of aluminium oxide
O2- —-> O2 + 4e-
Half equation at the cathode during electrolysis of molten aluminium oxide
Al3+ + 3e- —-> Al
Why can electrolysis take place in solutions
Ions are free to move to the electrodes
If a halide ion is present during electrolysis of solutions then it is always
Oxidised at the anode
If there is no halide ion in the electrolysis of a solution then _____ is oxidised at the anode instead
Oxygen
The ____ reactive cation ( + ion) remains in solution and the ____ reactive one is reduced at the cathode. ( If the cation is less reactive than hydrogen it will be formed at the cathode, if not hydrogen will be )
More
Less
Acid + Alkali —->
Salt + Water
Sulphuric acid + metal —->
Metal sulphate
Nitric acid + metal
Metal nitrate
