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Electrolysis LO: Describe what happens during electrolysis. (D) Explain what happens at the electrodes (C) Investigate what happens at the electrodes (B) Make conclusions about products formed based on reactivity (A) Starter Why do we write the sodium ion as Na+ ? Why do we write the chloride ion as Cl- ?

What happens during electrolysis ? - + Ions with a + charge go to the electrode with a – charge. It GAINS electrons here so it is not + anymore. Ions with a – charge go to the electrode with a + charge. It LOSES electrons here so it is not – anymore. A+ B-

Zinc Chloride Does solid zinc chloride conduct ? Why not ? What gas is given off ? What metal was left behind ? Why was this done in a fume cupboard ?

Electrolysis Electrolysis

Something with a + charge Gains electrons. Something with a – charge Loses electrons. We can write half equations to show this.

Half Equations Think about what happens at each electrode… Zn2+ + 2e-  Zn Cl- - e-  Cl

Practical 2 NaCl  2 Na + Cl2 Na+(aq) + e-  Na(s) Cl-(aq) - e-  Cl(g) The sodium reacts with water to make a gas. Which one ? 2 Na + 2 H2O  2 NaOH + H2

Oxidation and Reduction Oxidation Is Loss of electrons Reduction Is Gain of electrons OIL RIG

Which are oxidation and reduction ?

Uses for electrolysis Purification of copper Splitting sodium chloride to make sodium, chlorine or sodium hydroxide.