Design an electrolytic cell to demonstrate electrolysis in the class and represent the electrolytic cell with a well-illustrated diagram, keeping in mind the best choice for the electrolyte and the most suitable metal to be used as cathode and anode for electrolysis. Colour the various components of the electrolytic cell with relevant colours. The materials provided in the box given below are to be used as electrolytes and electrodes. Distilled water, tap water, copper sulphate, iron sulphate, sodium chloride, zinc sulphate, copper (Cu) strip, iron (Fe)strip, zinc (Zn)strip, aluminum (Al)strip. Write a conversation between the electrodes and the electrolytes to justify your choice.
Answers
Answer:
Explanation:
In the experiment, the \(\text{Cu}^{2+}\) ions from the \(\color{blue}{\textbf{blue copper(II) sulfate}}\) solution were reduced (gained electrons) to copper metal, which was then deposited as a layer on the solid zinc. The zinc atoms were oxidised (lost electrons) to form \(\text{Zn}^{2+}\) ions in the solution. \(\text{Zn}^{2+}(\text{aq})\) is colourless, therefore the blue solution lost colour. As discussed in Grade 11, the half-reactions are as follows:
\(\text{Cu}^{2+}(\text{aq}) + 2\text{e}^{-}\) \(\to\) \(\text{Cu}(\text{s})\) (\(\color{red}{\text{reduction half-reaction}}\))
\(\text{Zn}(\text{s})\) \(\to\) \(\text{Zn}^{2+}(\text{aq}) + 2\text{e}^{-}\) (\(\color{blue}{\text{oxidation half-reaction}}\))
The overall redox reaction is:
\(\text{Cu}^{2+}(\text{aq}) + \text{Zn}(\text{s})\) \(\to\) \(\text{Cu}(\text{s}) + \text{Zn}^{2+}(\text{aq})\)
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Figure 13.4: Solid zinc loses two electrons to form zinc ions (\(\text{Zn}^{2+}\)) in an aqueous solution of copper(II) sulfate. The copper ions (\(\text{Cu}^{2+}\)) gain two electrons and deposit as solid copper.
(Photos by benjah-bmm27 and Jurii on wikipedia)
Remember that there was an increase in the temperature of the reaction when you carried out this experiment (it was exothermic). An exothermic reaction releases energy. This raises a few questions:
Is it possible that this heat energy could be converted into electrical energy?
Can we use a chemical reaction with an exchange of electrons, to produce electricity?
If we supplied an electrical current could we cause some type of chemical reaction to take place?
The answers to these questions are the focus of this chapter:
The energy of a chemical reaction can be converted to electrical potential energy, which forms an electric current.
The transfer of electrons in a chemical reaction can cause electrical current to flow.
If you supply an electric current it can cause a chemical reaction to take place, by supplying the electrons (and potential energy) necessary for the reactions taking place within the cell.
These types of reactions are called electrochemical reactions. An electrochemical reaction is a reaction where:
a chemical reaction creates an electrical potential difference, and therefore an electric current in the external conducting wires
or
an electric current provides electrical potential energy and electrons, and therefore a chemical reaction takes place
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