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Investigation of energy changes in a displacement reaction

Extracts from this document...

Introduction

Investigation of energy changes in a displacement reaction

Introduction

The theory that I am looking at is that:

‘A more reactive metal will displace a less reactive metal from a compound’

The reaction that I will be looking at is zinc replacing copper. This happens, as zinc is higher in the reactivity series than copper. The ionic equation is shown below:

Zn(s) + Cu2+(aq) → Cu(s) + Zn2+(aq)

With any reaction with a more reactive metal, displacement occurs.

Plan

To make a prediction for this investigation, certain aspects of energy changes need to be looked into first:

Displacement reactions

Displacement reactions are type of redox reaction. These are reactions where a more reactive metal will replace a less reactive metal in a salt.

E.g. Zinc + Lead Nitrate → Zinc Nitrate + Lead

As zinc is more reactive, it replaces lead in the salt

Oxidation-reduction reactions, redox reactions, are an important part of this experiment. In an oxidation reaction, a product will gain oxygen ions and will loose electrons. In a reduction reaction, a product will loose oxygen ions and gain electrons. In the following example, copper reacts with oxygen ions to form copper oxide.

2Cu + O2 → 2CuO

The copper atoms are converted into copper ions Cu2+ in the reaction and the oxygen is converted into oxygen ions, O2-. The copper has lost electrons:

Cu → Cu2+ + 2 electrons

...read more.

Middle

Method

Apparatus

  • Polystyrene Cup
  • Beaker
  • Mercury Thermometer
  • Zinc (Chosen Masses)
  • Copper Sulphate (0.5M, 50cm3 at a time)
  • Measuring cylinder
  • Electronic weighing scales
  • Spatula
  • Goggles
  • Lab coat

Diagram

Method

  • Lab coat and goggles are put on
  • Polystyrene Cup is placed in the glass beaker
  • 50cm3 of copper sulphate is measured out and poured into the cup. The temperature of the copper sulphate is then taken and noted.
  • Zinc is measured out on electronic weighing scales and is added to copper sulphate
  • The copper sulphate and zinc are then stirred. When the reacting has stopped, the temperature is noted.
  • This process is repeated for the values every 0.25g from 0.25g to 3.0g. My values have gone past the maximum value to show the graph straightening out.

Variables

To make this experiment a fair test, certain variables need to be kept the same. The same person needs to be kept the same, so that the reaction speed is kept the same. Also, 50cm3 of copper sulphate needs to kept the same all the way through also, so that the reaction with the zinc will be fair. The 50cm3 measuring cylinder will have to be used, as the same error margin will be the same.

...read more.

Conclusion

  • Using a lid on the cup to keep the heat in
  • Using electronic scales which weigh to more than one decimal place to make the weighing more accurate
  • Using an electronic thermometer will increase the accuracy of the temperature measurement
  • Using a pipette or burette instead of a measuring cylinder will increase the accuracy of the measuring of the copper sulphate

The results I have found are reliable as the graphs match what was expected. The results have also been reproduced throughout the experiment.


Conclusion

My conclusion to this experiment is that it was fair and accurate method. It gave reliable results and the apparatus provided gave accurate results. However, these results can be improved further if:

  • More repartitions of the experiment were done. This would provide more results and add to the evidence for the experiment and also increase accuracy
  • The experiment was tried with different metals, ones that are at different levels in the reactivity series. This would be done to see how the use of different reactions change the temperature and energy changes and if the theory still works with different metals. Also, using salts with a metal lower in the reactivity series than the base can show whether distance in the reactivity series affects the energy change.
  • Different concentrations of the salt were used. This can also show the difference between the temperature and energy changes
  • Data logging could be used so that there is now chance in human error in the experiment

...read more.

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