Electrochemical series for SPM Chemistry is simply a collection of the standard electrode potential values being ordered in tables. Sometimes the volts as compared to the baseline is given. Here, the value of standard hydrogen electrode is used as the baseline and is set at 0. So, this Part 9 in the series of note on Electrochemistry for SPM Chemistry Form 4 students by Berry Berry Easy will be on the electrochemical series. This is a very important subtopic that appears in exams frequently.
[Tips: Come back to read this tip only when you are in Form 5, if you are in Form 4 now, please disregard this tip.
Students and teachers alike usually confuse electrochemical series with reactivity series especially during Form 5. Students sometimes mix up the two and get confused with the order.
In the reactivity series, it is ...K, Na, Ca, Mg and so on...
In the electrochemical series, it is ... K, Ca, Na, Mg and so on
The electrochemical series is based on a measured potential difference.The reactivity series also changes position due to the 'relative' nature of the series (meaning, order is relative to one chemical to another).]
SPM Chemistry Form 4 Notes – Electrochemistry (Part 9)
- It is an arrangement of elements according to their tendencies to donate electrons to form cations.
- Higher position in the series = a metal that has a higher tendencies to ionise and form positive ions.
- Electrochemistry is constructed by the potential difference (voltage difference) between pairs of metals and the ability of a metal to displace another metal from its own salt solution.
A) Electrochemical Series based on the Potential Difference (Voltage Difference)
- To construct an electrochemical series = measure the potential difference between two metals in voltaic cells.
- Negative terminal (anode) in voltaic cell has a higher tendency to release electrons = higher position in the electrochemical series (Positive terminal (cathode) in voltaic cell has a lower tendency to release electrons = lower position in the electrochemical series.
- The greater the potential difference (voltage) = further apart the positions of two metals in electrochemical series.
B) Electrochemical Series from the Displacement Reaction of Metals
- To construct an electrochemical series = ability of a metal to displace another metal from its salt solution.
- Higher position of a metal in the electrochemical series = able to displace a metal below it from its salt solution.
Mg(s) + CuSO4(aq) –> MgSO4(aq) + Cu(s)
- Mg is more electropositive than Cu (placed higher than copper in electrochemical series)
- Mg atom loses electrons to form magnesium ion and dissolves in the solution.
This end Part 9 in the series of note on Electrochemistry for SPM Chemistry Form 4 students by Berry Berry Easy. In the next part (final Part 10), Berry Readers will learn about the importance of the electrochemical series. A very simple subtopic once you understand this part.