chemictry PEKA

Name Class IC No Date Title

: : : : 16 August 2011 : Experiment 6.7 The electrochemical series

Aim : To construct the electrochemical series based on potential differences between metals. Problem statement : Can an electrochemical series of metals be constructed based on the potential difference between two metals? C1PI1(i) Hypothesis : By using different pairs of metals and determining the negative terminal and cell voltage, an electrochemical series can be constructed. Variables : Manipulated variable : Type of metal Responding variables : The cell voltage and the negative terminal Fixed variables : The type and concentration of electrolyte, copper electrode C1PI1(ii) Materials : Dilute sulphuric acid,H2SO4 , copper strips, lead strip, iron strip, zinc strip, aluminium strip. Magnesium strip, sandpaper Apparatus : Voltmeter, beaker, connecting wires with crocodile clips C1PI1(iii) Procedure : Voltmeter

V Electrode B Electrode A

Dilute sulpuric acid, H2SO4 1. The metals are cleaned with sandpaper. 2. A beaker is filled with dilute sulpuric acid, H2SO4 until it is two-third full. 3. The magnesium strip as electrode A and copper strip as electrode B is dipped into dilute sulpuric acid, H2SO4. 4. The magnesium strip and copper strip is connected to the voltmeter using connecting wires.

5. The potential difference between the metals is recorded. 6. Which metal strip is the negative terminal is determined and recorded. 7. Steps 1 to 6 is repeated using other metals to replace magnesium as electrode A. C1PI1(iv)

Data and observation : Pair of electrodes

Potential difference (V) 2.0 1.6

Negative terminal of the cell Magnesium Aluminium

Zinc and copper

0.9

Zinc

Lead and copper

0.3

Lead

Iron and copper

0.5

Iron

Magnesium and copper Aluminium and copper

Interpreting data : 1. Magnesium produces the highest potential difference with copper. 2. Iron produces the lowest potential difference with copper. 3. The arrangement of the metals in decreasing tendency to donate.

Electropositivity decrease

Magnesium Aluminium Zinc Iron Copper C4PI1

Discussion : 1.

a) Copper metal is the positive terminal when paired with magnesium. b) Magnesium electrode is the negative terminal. 2. a) The positive terminal becomes thinner. b) The negative terminal becomes thicker. 3. The direction of electron flow from the negative terminal to the positive terminal. C4PI2 Conclusion : (copy your hypothesis). Hypothesis is accepted.

C1PI1( v) C1 C3PI 1 C3PI 2 C3PI 3 C3