Reactivity of Metals
Specification Point 4.1:
Deduce the relative reactivity of some metals, by their reactions with water, acids and salt solutions.
- The chemistry of metals is studied by analysing their reactions with water, dilute acid and salt solutions.
- Based on these observations a reactivity series of metals can be produced.
Reactivity with Water
- Some metals react with water, either warm or cold, or with steam.
- Metals that react with cold water form a metal hydroxide and hydrogen gas, for example calcium:
Ca + 2H2O → Ca(OH)2 + H2
- Metals that react with steam form metal oxide and hydrogen gas, for example zinc:
Zn + H2O → ZnO + H2
Reactivity with Acids
- Most metals react with dilute acids such as HCl.
- When acids and metals react, the hydrogen atom in the acid is replaced by the metal atom to produce a salt and hydrogen gas, for example iron:
Fe + 2HCI → FeCl2 + H2
Reactivity with Oxygen
- Unreactive metals such as gold and copper do not react with acids.
- Some reactive metals such as the alkali metals react with oxygen.
- Copper and iron can also react with oxygen although much more slowly.
- When metals react with oxygen a metal oxide is formed, for example copper:
2Cu + O2 → 2CuO
Reactivity with Salt Solutions
- The reactivity between two metals can be compared using displacement reactions in salt solutions of one of the metals.
- This is easily seen as the more reactive metal slowly disappears from the solution, displacing the less reactive metal.
- For example magnesium is a reactive metal and can displace copper from a copper sulfate solution:
Mg + CuSO4 → MgSO4 + Cu
- The blue color of the CuSO4 solution fades as colorless magnesium sulfate solution is formed.
- Brown copper metal coats the surface of the magnesium and also forms solid metal which falls to the bottom of the beaker.
Diagram showing the colour change as magnesium displaces less reactive copper from CuSO4
Reactivity Series of Metals
Specification Point 4.3:
Explain the reactivity series of metals (potassium, sodium, calcium, magnesium, aluminium, (carbon), zinc, iron,(hydrogen), copper, silver, gold) in terms of the reactivity of the metals with water and dilute acids and that these reactions show the relative tendency of metal atoms to form cations.
- Metal atoms form cations (+vely charged ions) when they react with other substances.
- More reactive metals tend to form cations more readily than less reactive metals.
- The reactivity series organises the metals in order of their reactivity which is essentially a measure of how willingly they form cations.
- Metals higher up on the series react more violently than those further down and are oxidised much more easily.
- Metals further down are much less reactive and do not lose their electrons easily, hence they resist oxidation.
- Carbon and hydrogen are non-metals, but are included in the series as they are useful in the extraction of metals from their ores.
Reactivity Series Mnemonic
- “Please send lions, cats, monkeys and cute zebras into hot countries signed Gordon”.
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Morgan’s passion for the Periodic Table begun on his 10th birthday when he received his first Chemistry set. After studying the subject at university he went on to become a fully fledged Chemistry teacher, and now works in an international school in Madrid! In his spare time he helps create our fantastic resources to help you ace your exams.
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