Below is a question contributed by a local chemistry student (Student X)?and an avid reader of this Chemistry Blogsite.
This will be a question that combines Mole Calculations & Qualitative Analysis topics. Give it a try!
In an experiment, 4.0cm^3 of 1.0mol/dm^3 aqueous copper(II) sulphate was mixed with 8cm^3 of 1.0mol/dm^3 aqueous sodium carbonate:
CuSO4 + Na2CO3 –> Na2SO4 + CuCO3
What did the reaction vessel contain when the reaction was completed?
A. A colourless solution only
B. A green precipitate and a blue solution
C. A green precipitate and a colourless solution
D. A blue precipitate and a blue solution
Student X?s suggested answer:
What I think: copper sulphate is the limiting reactant, hence sodium carbonate is in excess. Hence, when the reaction is completed, only excess sodium carbonate remains. So, the solution remains colourless and my answer is C.
My Suggested Answer:
I agree that the Answer is C. At the end of the reaction, we will see a Green Precipitate of Copper Carbonate(s) which is insoluble in water. There will also be a colourless solution that is contributed by both the product Sodium Sulphate(aq) and the excess reactant Sodium Carbonate (aq) which are soluble in water. (Click the image below to have a clearer understanding)
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