Wednesday, 21 January 2015

6.6.2 - Laboratory Activity : Constructing an electrochemical series based on the displacement of metals

Laboratory Activity 6.6.2:
Constructing an electrochemical series based on the displacement of metals
Aim: To construct the electrochemical series based on the ability of a metal to displace other metals from its salt solution
Problem statement: How can the electrochemical series be constructed from the displacement reaction of a metal from its salt solution by other metals?
Hypothesis: Electrochemical series can be built from the principle that metals located higher in the electrochemical series can displace other metals located lower in the series from its salt solution.
» Fixed variable : Concentration of electrolytes
» Manipulated variable : Different metals
» Responding variable : Change in colour sediment formed

» Zinc chloride
» Iron (III) nitrate
» Copper(II) sulphate solution
» Lead(II) nitrate
» Magnesium chloride
» Zinc plate
» Iron nail
» Copper plate
» Lead strip
» Magnesium strip

» Test tube
» Sand paper

1. All the metals are cleaned with sand paper.
2. 10cm3 of copper(II) sulphate is poured into 5 different test tubes.
3. A different metal(Cu, Zn, Fe, Pb, and Mg) is dropped into each test tube.
4. All observation on the changes of solution and metal formed on the surface of metal are recorded.
5. The experiment is repeated using iron, zinc, lead and copper.

The animation below shows the results of the experiment.

Metal Copper sulphate Lead(II) nitrate Iron(III) nitrate Zinc chloride Magnesium chloride
Copper -
Lead -
Iron -
Zinc -
Magnesium -
✔ - displacement reaction occurred
✘ - displacement reaction did not occur

Copper is the least electropositive of the 5 metals as it cannot displace any of the other metals from their salt solutions.

Magnesium is the most electropositive of the metals as it displaces all the other metals from their salt solution.

Based on the results of the experiment, the electrochemical series can be constructed by arranging metals that are more electropositive first:

The metal which is more electropositive will displace the less electropositive metal from its salt solution.

The hypothesis is accepted.

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