🚨 Frequently asked in IGCSE Chemistry 🚨
Reactivity Series Based on Water and Dilute Acid
- Metals can be organized based on their reactivity with water and dilute acid.
- Although carbon and hydrogen are non-metals, they are often included in the reactivity series for reference.
- The more reactive elements are placed on top of the reactivity series, and the less reactive elements are placed at the bottom of the reactivity series.
- The elements on the top reacts more vigorously and quickly while the elements at the bottom reacts more slowly.
Displacement Reactions
A displacement reaction happens when a more reactive metal displaces a less reactive metal.
I. Displacement Reactions of Metal Oxides
EXAMPLES
CuO + Mg → MgO + Cu
The more reactive magnesium displaces copper from copper oxide.
ZnO + Ca → CaO + Zn
The more reactive calcium displaces zinc from zinc oxide.
Na2O + Mg → no reaction
The less reactive magnesium cannot displace sodium, so no reaction happens.
II. Displacement Reactions of Salts
EXAMPLES
CuSO4 + Zn → ZnSO4 + Cu
The more reactive zinc displaces copper from copper sulfate.
Pb + 2AgNO3 → Pb(NO3)2 + 2Ag
The more reactive lead displaces silver from silver nitrate.
Cu + CaCl2 → no reaction
The less reactive copper cannot displace calcium, so no reaction occurs.
👇Questions from past IGCSE Chemistry exams 👇
Question I
This question is about the reactions of some metals and their compounds. A student adds a sample of four metals R, S, T and U separately to water and to dilute sulfuric acid. The table shows the observations in each experiment.
(a) State two properties of the metals that the student should keep the same in all of the experiments in order to compare their reactivity.
- Amount of metal in moles
- Surface area of metal
(b) Place the metals in order of decreasing reactivity.
- S > U > R > T
- Since metal S reacts with both dilute sulfuric acid and water quickly, it is the most reactive metal.
- T is the least reactive since it reacts with neither water nor dilute sulfuric acid.
- U is more reactive than R because
- U reacts with dilute sulfuric acid more quickly than R. and
- U reacts with water, but R does not react with water.
Question 2
The thermite reaction is used on railways to produce molten iron for joining rails together. The equation for this thermite reaction is
2Al + Fe2O3 → Al2O3 + 2Fe
What does this reaction show about the reactivity of iron compared to the reactivity of aluminium?
- In the thermite reaction, aluminum displaces iron from iron oxide.
- This means that aluminum has a higher reactivity than iron.
Question 3
A student carries out an investigation to compare the reactivities of four metals, aluminium, copper, zinc and M. He adds strips of zinc to the aqueous solutions of the nitrates of each metal. After a few minutes he removes the strips of zinc and examines them. The table shows his results.
(a) Explain why there is a brown coating on zinc for copper(II) nitrate solution.
Zinc is more reactive than copper, so zinc displaces copper from its salt. The products of the reaction are zinc nitrate and copper.
Zn + Cu(NO3)2 → Cu + Zn(NO3)2
Copper is the substance that causes brown coating on zinc.
(b) State why there is no change in the experiment with aluminum nitrate solution.
Zinc is less reactive than aluminum, so zinc cannot displace aluminum from its salt, and no reaction happens.
(c) The student repeats the experiment with strips of metal M instead of strips of zinc. The table shows his results.
Using information from both tables of results, place the metals aluminium, copper, zinc and M in order of decreasing reactivity.
- aluminum > zinc > M > copper
- From first experiment,
- zinc cannot displace aluminum, so zinc is less reactive than aluminum.
- zinc displaces copper, so zinc is more reactive than copper.
- zinc displaces M, so zinc is more reactive than M.
- From second experiment,
- M displaces copper, so M is more reactive than copper.