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Chemical Changes (Acids and Alkalis (Acids have a pH of around 1., Alkalis…
Chemical Changes
Acids and Alkalis
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Strong Acids fully dissociate into hydrogen ions. Weak Acids partially dissociate into hydrogen ions
Strong Alkalis fully dissociate into hydroxide ions. Weak Alkalis partially dissociate into hydroxide ions.
Concentrated acids or alkalis have a large number of hydroxide or hydrogen ions in a dissolved solution. Dilute acids have less hydroxide or hydrogen ions in a dissolved solution.
Electrolysis
Electrolysis is an extraction method that involves passing a current through a molten or dissolved ionic compound.
There are two electrodes. One positive : the anode. One negative : the cathode. They are made of unreactive metals or graphite to avoid unwanted side reactions.
In the electrolysis of molten compounds, positive ions move towards the cathode to be reduced. Negative ions move to the anode and are oxidised. This is because opposite charges attract.
In the electrolysis of dissolved compounds, if the metal ions are more unreactive than hydrogen in the reactivity series then they will be reduced otherwise hydrogen will be reduced at the cathode. At the anode, if a halide ion can be oxidised then it will, otherwise hydroxide ions will be oxidised instead.
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Reactivity series
Potassium
Sodium
Lithium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Tin
Lead
Hydrogen
Copper
Silver
Gold
Platinum
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