Make-Up Assignment for Laboratory Experiment 6 Name: The chemical formula of blu

Question

Make-Up Assignment for Laboratory Experiment 6 Name: The chemical formula of blue copper sulfate is CuS04.5HO. Determine the mass percentage of water in blue copper sulfate. 1. 2 You may be able to separate NH/CI, NaCI and SO2 from their mixture in a different order that what you actually did in the laboratory. Explain. 3. Suppose you weighed 2003 g sample of a mixture of NH,C, NaCl and SO2. Accidently you dropped a small amount of the sample on the floor. Nevertheless, you decided to carryout the experiment without further weighing the mixture. How would the individual mass percentage of NH,CI, Nadl and SiO2 be affected?

Explanation / Answer

1) Molar mass of blue copper sulfate , CuSO4. 5H2O = 249.685 g/mol

There are five water molecules in blue copper sulfate so the molar mass of water = 5 x 18.01528= 90.0764 g/mol

Now, mass % of water = (molar mass of water / molar mass of blue copper sulfate) x 100 %

=> mass % of water =( 90.0764 / 249.685) x 100 % = 0.3607 x 100 % = 36.07 %

2) The separation of NH4Cl , NaCl and SiO2 from their reaction mixture---

Steps are as follows--

a) Firstly we heat the mixture (no water should be present) at around 3200C, the NH4Cl will sublime away. At that point, let it cool and we can isolate the NaCl by removing with water (SiO2 is insoluble).

b) The extraction of water could be done at first to separate the SiO2 . After that, we dry and heat the NaCl/ NH4Cl mixture in order to sublime the ammonium chloride (NH4Cl) away.

c) We could attempt fractional crystallization, yet we won't accomplish complete separation, as the solubility of NH4Cl drops from around 76g/100ml to around 30g/100ml and solubility of NaCl drops from around 39g/100ml to around 36g/100ml on going from 1000C to 200C.

3) Mixture weight = 2.003 g

There would be a minimal error if a small amount of sample is dropped on the floor accidentally. The individual mass % would also be affected accordingly.

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