Behavior of zinc compounds and its decomposition
- Zinc compounds are maily colourless
- When heated, most zinc compounds decompose to zinc oxide.
- Hot zinc oxide turns yellow, whilst cooled zinc oxide turns white.
- Thermal decomposition is generally an endothermic reaction, since it requires energy to break a bond which is essentially all that a decomposition reaction is doing.
- Zinc is a transition metal with no empty D-orbitals.
- The end of zinc's electronic configuration is 3D(10)4S(2), so it generally behaves as a group 2 metal. This also means that in ion form, zinc has a charge of +2.
- The equation for the thermal decomposition of Zinc Carbonate is ZnCO3(s) --> ZnO(s) + CO2(g)
Reacting ZnCO3 with an acid
This is an acid/base reaction.
With sulphuric acid: ZnCO3(s) + H2SO4 --> ZnSO4 (aq) + CO2(g) + H2O(g)
With hydrocholic acid: ZnCO3(s) + 2HCl --> ZnCl2 (aq) + H2O + CO2
- Both will bubble and dissolve to form a soluble salt.
- When no more carbonate dissolves, the acid has been neutralised.
- The undissolved carbonate can be removed through filtration.
With sodium hydroxide: ZnCO3 (s)+ 2NaOH (aq)---> Zn(OH)2(s) +Na2CO3 (aq)