Page 1 - Dae Koon
Observations :
The colour changes from colourless to blue, and the powder disappears.The blue colour intensifies as more black powder is used.
Page 2 - Fanpu
Colour of filtrate: blue
Colour of residue: black
Name of filtrate: Copper (II) sulfate and water
Name of residue: Copper (II) oxide
1. H2SO4 + CuO --> CuSO4 + H2O
2. Blue
Page 3 - Joel Chua
3. Take a few of the Copper(II) sulfate crystals and place them on a cleaned, dry evaporating dish and heat for a few minutes.
a ) State and explain your observation.
The blue Copper(II) sulfate crystals becomes white Copper(II) sulfate powder. When Copper(II) sulfate is heated, it becomes dehydrated, and water is removed from it. The dehydrated compound that is formed is white. Hence, the Copper(II) sulfate changes from blue to white.
b) Add one drop of water on the residue left in a. State and explain your observations.
The residue in a turns blue. Previously, when the Copper(II) sulfate was heated, it became dehydrated, and the compound formed was white. However, when water is added to it, it becomes hydrated again, and turns back to its original colour, which is blue.
Page 4 - Zhao Xiang
4.Colour of filtrate: Blue
Colour of residue: white
Name of residue: lead(II)sulfate
1.Word equation: Pb(NO3)2 + CuSO4 --> PbSO4 + Cu(NO3)
Chemical equation: Pb(NO3)2 + 2CuSO4 --> 2PbSO4 + 2Cu(NO3)
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