Chapter 6 - Electrolysis
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What is electrolysis?
The breakdown of a substance using electricity.
What is the substance broken down by electrolysis called?
The electrolyte.
State the scientific name for the positive and negative electrode.
P - anode N - cathode
Why can ionic compounds only be electrolysed when it is in a molten/liquid state?
The compounds ions can freely move and carry charge to electrodes.
State which ion travels to which electrode.
Positive ions - Cathode (N) Negative ions - Anode (P)
What happens to the ions at the anode?
They are reduced (gained electrons).
What happens to the ions at the anode?
They are reduced (gained electrons).
What happens to the ions at the anode?
They are reduced (gained electrons).
What is formed at each electrode during the electrolysis of copper chloride solution?
Cathode - Copper Anode - Chlorine
State the half equations for the electrolysis of aluminium oxide at each electrode. Aluminium - Al2O3 Oxygen - O2
Cathode - Al3+ + 3e- = Al Anode - 2O2- = O2 + 4e-
Which ions are reduced and oxidised during the electrolysis of aluminium oxide?
Aluminium ions are reduced. Oxygen ions are oxidised.
What is aluminium oxide mixed with before electrolysis?
Molten cryolite.
Why are positively charged ions attracted to the cathode?
The cathode is negatively charged, so positive charges will attract.
Define electrode.
A rod conducting electricity. 1 positive and 1 negative.
What happens to ionic compounds in electrolysis?
They are turned into elements via electrolysis
What happens to ionic compounds in electrolysis?
They turn into elements via electrolysis
State the three products produced when a student electrolyses sodium chloride solution.
• Chlorine gas (anode) • Hydrogen gas (cathode) • Sodium hydroxide
How is chlorine attracted to the anode?
Negative chlorine ions (Cl-) are formed and attracted towards the anode, as opposites attract.
A student is trying to perform an electrolysis of copper (II) chloride solution. Describe an effective experiment to perform this electrolysis [6].
Measure 50cm3 of copper chloride solution into a beaker. [1] Place lid with carbon rods over beaker [1] Attach leads to rods and connect with a power supply [1] Set pack at 4V for 5 minutes [1] Use litmus paper to test for chlorine. If paper is bleach, chlorine is present. [1] After 5 minutes, turn off power supply and check electrode surface for copper coatings, which are coppery-red [1]
What happens to ions at the cathode?
They are oxidised (loses electrons)