Sunday, July 9, 2017

3.18: Describe Reversible Reactions such as the Dehydration of Hydrated Copper (II) Sulfate and the Effect of Heat on Ammonium Chloride



REVERSIBLE REACTIONS: Reaction that can occur in both directions (reactants can react to form products, and products can react to form initial reactants)
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DEHYDRATION OF HYDRATED COPPER (II) SULFATE:
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DEHYDRATION OF HYDRATED COPPER (II) SULFATE
Diagram showing the Dehydration of Hydrated Copper (II) Sulfate
EXPLANATION:

  • Copper (II) Sulfate crystals that contain Water are known as Hydrated Copper (II) Sulfate
  • When Hydrated Copper (II) Sulfate crystals are heated in test tube, blue crystals will turn into white powder, and colourless liquid will collect at the top
  • This is because when Hydrated Copper (II) Sulfate crystals are heated, it loses Water of Crystallisation and turns into Anhydrous Copper (II) Sulfate (white powder) and Water (colourless liquid):


  CuSO4.5H2O (s)      ⇌       CuSO4 (s)     +     5H2O (l)


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EFFECT OF HEAT ON AMMONIUM CHLORIDE:
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THERMAL DECOMPOSITION OF AMMONIUM CHLORIDE
Diagram showing the Thermal Decomposition of Ammonium Chloride
EXPLANATION:

  • When Ammonium Chloride is heated in a test tube, white crystals at the bottom disappears and reappears further up, with colourless Gas forming in between
  • This is because heating Ammonium Chloride causes it to decompose into Ammonia (colourless gas) - NH3+, and Hydrogen Chloride - HCl:

  CNH4Cl (s)      ⇌       NH3 (g)     +     HCl (g)

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