Thermal decomposition of zinc carbonate

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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)
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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)

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