Displacement reactions involving solutions of salts
4 marks · NormalThe table below shows observations from adding different metals to solutions of salts.
| Metal added | Solution | Observation |
|---|---|---|
| Zinc | Copper(II) sulfate | Brown solid forms; blue solution fades |
| Copper | Silver nitrate | Grey crystals form; colourless solution turns blue |
| Iron | Magnesium sulfate | No visible change |
For each reaction in the table, write the full ionic equation showing the species that change during the reaction. Where no reaction occurs, state why.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
1) Zn(s) + Cu^{2+}(aq) -> Zn^{2+}(aq) + Cu(s); 2) Cu(s) + 2Ag^{+}(aq) -> Cu^{2+}(aq) + 2Ag(s); 3) No reaction because iron is less reactive than magnesium.
Common mistakes: Including spectator ions; Writing molecular instead of ionic equations
Show mark scheme and worked solution
Marking points
M1 · 1 mark · Correct ionic equation for Zn + Cu^{2+}; equation only includes species that change.
M2 · 1 mark · Correct ionic equation for Cu + Ag^{+}, with balancing and charges.
M3 · 1 mark · States 'no reaction' for Fe + MgSO_4 and gives correct explanation based on reactivity.
A1 · 1 mark · All formulae, charges, and balancing correct for all equations.
Worked solution
1) For zinc and copper(II) sulfate:
2) For copper and silver nitrate:
3) For iron and magnesium sulfate: no reaction – iron is less reactive than magnesium, so it cannot displace magnesium from its salt.