A​​ student​​ investigated​​ the​​ temperature​​ change​​ in​​ displacement​​ reactions​​ between metals and copper sulfate solution.​​ 

Table​​ 2​​ shows​​ the​​ student’s​​ results.​​      

Table​​ 2

Plot the​​ data​​ from​​ Table​​ 2​​ on​​ Figure​​ 4​​ as​​ a​​ bar​​ chart.​​   

[2 marks]

ANSWER

The​​ student​​ concluded​​ that​​ the​​ reactions​​ between​​ the​​ metals​​ and​​ copper​​ sulfate solution are endothermic.​​ 

Give​​ one​​ reason​​ why​​ this​​ conclusion​​ is​​ not​​ correct.​​   

[1​​ mark]

ANSWER

Since there is increase in temperature therefore it is exothermic reaction not endothermic.​​ 

The​​ temperature​​ change​​ depends​​ on​​ the​​ reactivity​​ of​​ the​​ metal.​​ 

The​​ student’s​​ results​​ are​​ used​​ to​​ place​​ copper, iron,​​ magnesium​​ and​​ zinc​​ in​​ order​​ of their reactivity.​​ 

Describe​​ a​​ method​​ to​​ find​​ the​​ position​​ of an​​ unknown​​ metal​​ in​​ this​​ reactivity​​ series. Your method should give valid results.  

[4​​ marks]

ANSWER

First step is to add the unknown metal to copper sulfate solution. Secondly, measure temperature change.​​ 

Thirdly, Repeat the process for all the metals of Table 2 and record temperature change of each.

Fourthly, place the metals in order of temperature change.​​ 

Control Variables:

• Same volume of solution​​ 

• Same concentration of solution​​ 

• Same mass / moles of metal​​ 

• Same state of division of metal

Draw​​ a​​ fully​​ labeled​​ reaction​​ profile​​ for​​ the​​ reaction​​ between​​ zinc​​ and copper sulfate solution on Figure 5.​​      ​​ ​​ ​​ ​​​​ 

[3​​ marks]

Figure​​ 5

ANSWER