C6.2 Changes at the electrodes
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What happens when ions reach an electrode?
They either lose or gain electrons
What do negatively charged ions do to become neutral?
They lose electrons at the anode
What do positively charged ions do to become neutral?
They gain electrons at the cathode
Describe what happens to the Pb +2 ions as they move towards the cathode in the electrolysis of molten lead bromide?
The Pb 2+ ions gain 2 electrons at the cathode and become neutral
Describe what happens to the Br- ions as they move towards the anode in the electrolysis of molten lead bromide?
Each Br ion loses an electron to become neutral. The two bromine atoms form a covalent bond to form a bromine molecule
What is called when a metal gains an electron?
Reduction
What is called when a non-metal loses an electron?
Oxidation
What is the half equation at the cathode when Pb +2 ions arrive?
Pb+2 + 2e- → Pb
What is the half equation at the anode when Br- ions arrive?
2Br- → Br(2) molecule + 2e-
What substance will be produced in the electrolysis of an aqueous solution?
The less reactive one
What is produced at the cathode in the electrolysis of a potassium compound in an aqueous solution and why?
There are H+ ions in the electrolyte with K+ ions Both the ions will be attracted to the cathode The hydrogen ions are less reactive than the potassium ions This means hydrogen gas is produced at the cathode
What is the half equation at the cathode in the electrolysis of a potassium compound (aq)?
2(+H) + 2e- → H(2) molecule
What happens at the anode in the electrolysis of an aqueous solution?
Usually oxygen gas
What is the half equation when hydroxide ions discharge at the anode?
4OH-(aq) → 2H(2)O(l) + O(2)(g) + 4 e-
What is produced at the anode if there is a halide ion involved?
The halide ion