reactivity and extraction of metals Flashcards
how is order of reactivity arranged based on reactions with water and acid?
it can be determined by adding acid to different metals and observing the rate of reaction.
Instead of using acid, water can be used to test the relative reactivity of metals. However, many metals are too low in the reactivity series to react with water
how is order of reactivity arranged based on displacement reaction between metals and metal oxides, metals and aqueous solutions of metal salts
A metal will displace another metal from its oxide that is lower in the reactivity series.
e.g. a reaction with magnesium and copper (II) oxide will result in the magnesium displacing the copper from its oxide
A metal will also displace another metal from its salt that is lower in the reactivity series.
e.g. the reaction between zinc and copper (II) sulfate solution will result in zinc displacing the copper from its salt:
order of the reactivity series
Potassium
Sodium
Lithium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Hydrogen
Copper
Silver
Gold
when does iron rust?
when both oxygen and water are present
iron + oxygen + water –> hydrated iron(III) oxide (rust)
4Fe +3O2 +H2O –> 2Fe2O3H2O
3 methods of preventing rust
- galvanising
- barrier methods
- sacrificial protection
how does galvanising work?
coating in zinc prevents water and oxygen getting to the iron, but with galvanising even if the barrier is broken the more reactive zinc corrodes before the less reactive iron.
how does the barrier method work?
Rusting may be prevented by stopping the water and oxygen getting to the iron with a barrier of grease, oil, paint or plastic.
how does sacrificial protection work?
zinc bars can be attached to iron. The zinc will oxidise and therefore corrode first, protecting the iron from corrosion. Zinc is more reactive than iron therefore will lose its electrons more easily than iron and is oxidised more easily.
what is oxidation
- the loss of electrons. e.g. a sodium atom (Na) loses an electron to become a sodium ion (Na⁺).
OR - the gain of oxygen. e.g. if carbon combines with oxygen to form carbon dioxide, the carbon is being oxidised.
what is reduction
- the gain of electrons. e.g. a sodium ion (Na⁺) gains an electron to become a sodium atom (Na).
OR - the loss of oxygen.e.g. when aluminium oxide is broken down to produce aluminium and oxygen, the aluminium is being reduced.
what is redox
A reaction involving oxidation and reduction.
whats an oxidising agent
A substance that gives oxygen or removes electrons (it is itself reduced).
whats a reducing agent
A substance that takes oxygen or gives electrons (it is itself oxidised).
practical: investigate reactions between dilute hydrochloric and sulfuric acids and metals (e.g. magnesium, zinc and iron)
Metals above hydrogen in the reactivity series will react with dilute hydrochloric or sulfuric acid to produce a salt and hydrogen.
metal + acid → salt + hydrogen
e.g. magnesium + hydrochloric acid → magnesium chloride + hydrogen
Mg (s) + 2HCl (aq) → MgCl₂ (aq) + H₂ (g)
This is a displacement reaction.
There is a rapid fizzing and a colourless gas is produced. This gas pops with a lighted splint, showing the gas is hydrogen.
The reaction mixture becomes warm as heat is produced (exothermic).
The magnesium disappears to leave a colourless solution of magnesium chloride.
If more reactive metals are used instead of magnesium the reaction will be faster so the fizzing will be more vigorous and more heat will be produced.
equation for rust
iron + water + oxygen –> hydrated iron(III) oxide
