Question

Introduction
The chemical reactions involved in this experiment are:
CuSO4(aq) + Zn(s) → ZnSO4(aq) + Cu(s)
Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g)
The copper on the surface quickly reacts with oxygen according to the following reaction:
2Cu(s) + O2(g) → 2CuO(s)

Experimental Procedure
Dissolve completely about 0.5 to 0.7 g of copper (II) sulphate pentahydrate in about 10 to 20 mL of deionized
water.
Calculate the amount of zinc powder that must be added to a copper sulfate solution so that the sulfate
completely reacts. This calculated mass of zinc, plus an extra 0.01 g, is added to the copper sulfate. Stir.
When the reaction appears to be complete (what signifies this?), add enough sulfuric acid to create a
colourless solution. What is the purpose of this step?
Suction filter the final product. Wash with about 5 mL of ethanol. Maintain suction for about 10 minutes.
Determine the mass of the final product to 2 significant figures.
Reagents
0. 6 g Copper (II) sulfate pentahydrate (CuSO4(s)) (FW = 249.68)
Zinc powder (FW = 65.41)
Sulfuric acid (1.5 M H2SO4(aq))
Ethanol

Data
Mass of CuSO4 = 0.61g
Mass of Zn = 0.17g
Mass of empty watch glass = 48.72g
Mass of watch glass and Cu = 48.91g

Questions:

1. Please show the calculation for the amount of Zn added to the reaction mixture and for the percentage of Cu recovered from the original copper sulfate sample.

2. What is the purpose of adding enough sulfuric acid to create a colourless solution?

Answer 1

The mass of Cu recovered is higher than the expected mass this is due to presence of the impurity (CuO) which is formed during reaction.

1. Mass of copper (11) sulfate pentah Copper (11) sulfate penta imperate taken=o. dg. Molar reass of cusou. 51420= 249.68 g/mol Moles of chin 0.61 g 249.68 /mol no 2.443x10-3 mole - Moles of an regnired for complete reduction of cut = 2.443x10 3 mole, 8. Fw of an - 65.41g/mer to buy i mass of an regnired for reduction, = 65.41 x 2.443x10 g 0.1598 9. s 0.16g. r. Toral mass of n taken = 0.16 +0.01g. - 0.17 g Mass of empty watch glass = 48.72 g. reass of watch glassten = 48.91g. : Mass of en formed - 48.91-48.7.2 = 0.19g. Molar mass of cn = 63.55 g/mol & expected mass of en to be formed a = 63.55x 2,443 4103 a 0.155g. But here we get on lag cu solid, so there is a change of of the presence of impurity in collected cu solid. Therefore, it may be 100%. Cu recovered from original Copper sulfate Solution with some of impurities.