This reaction is used in a metal-recovery workshop to coat zinc scraps with copper. A strip of zinc is placed in blue copper sulfate solution. After the rea...
Question 1 Report
This reaction is used in a metal-recovery workshop to coat zinc scraps with copper. A strip of zinc is placed in blue copper sulfate solution. After the reaction, a reddish-brown solid is collected and dried. Fig. 1 shows the beaker before and after the reaction. The equation is Zn + CuSO4 → ZnSO4 + Cu. Relative atomic masses are Zn = 65 and Cu = 63.5. The student starts with 6.50 g of zinc and an excess of copper sulfate solution.
(a) Name the reddish-brown element collected. [1]
(b) What observation shows that copper sulfate solution is being used up? [1]
(c) Use the equation to give the moles of copper formed from 0.100 mol of zinc. [1]
(d) Use the relative atomic mass to calculate the moles of zinc in 6.50 g. [2]
(e) Give the mass of copper expected if all 6.50 g of zinc reacts. [2]
(f) Use your answer to part (e) to calculate the change in mass of the solution. [2]
Answer Details
- (a) The reddish-brown element is copper. [1]
- (b) The blue solution becomes paler or loses its blue colour as copper sulfate is used up. [1]
- (c) The equation has a \(1:1\) ratio, so \(0.100\) mol zinc forms 0.100 mol copper. [1]
- (d) \[\text{moles Zn}=\frac{6.50}{65}=0.100\text{ mol}\] [2]
- (e) \[0.100\times63.5=6.35\text{ g copper}\] [2]
- (f) \(6.50\) g zinc enters the solution and \(6.35\) g copper leaves it. [1] \[6.50-6.35=\mathbf{0.15\text{ g}}\] The solution mass increases by \(0.15\) g. [1]
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