ELECTROLYSIS EXAM 2025/2026 QUESTIONS WITH
ANSWERS GRADED A+
✔✔What happens to Pb2+ at the cathode? - ✔✔a lead ion accepts/gains two electrons
to become a lead atom. (Pb)
✔✔What happens to the molten lead formed at the cathode when Pb2+ gains 2
electrons? - ✔✔it will sink to the bottom.
✔✔what is the half equation to show what happens to Pb2+ at the cathode? -
✔✔Pb2+(l) + +2e - ---> Pb(l)
✔✔Which electrode are the bromide (Br-) ions attracted to? - ✔✔the anode (positive
electrode)
✔✔what happens to Br- at the anode? - ✔✔Two bromide ions lose one electron each
and become a bromine molecule (Br2). Brown bromine gas forms at the top of the
anode.
✔✔a word to describe splitting up a compound: - ✔✔decomposing
✔✔What is the half equation to show what happens to Br- at the anode? - ✔✔2Br-(l) ----
> Br2(g) + 2e-
✔✔example of molten salts can be used for electrolysis: - ✔✔lead bromide (PbBr2)
✔✔Why don't electrodes react? - ✔✔because they are made of inert (unreactive
material)
✔✔In electrolysis of aqueous solutions, what other two ions will there be as well as the
ions from the ionic compound? - ✔✔Hydrogen ions (H+)
Hydroxide ions (OH-)
✔✔How come there are hydrogen ions and hydroxide ions in aqueous solutions but not
molten? - ✔✔Because there is water in aqueous solutions.
✔✔What happens at the cathode with aqueous solutions if the metal ions are more
reactive than the H+ ions? - ✔✔If the metal ions are more reactive than the H+ ions (e.g
sodium ions), hydrogen gas will be produced.
✔✔what happens at the cathode with aqueous solutions if the metal ions are less
reactive than the H+ ions? - ✔✔If the metal ions are less reactive than the H+ ions (e.g
copper ions), a solid layer of the pure metal will be produced instead.
, ✔✔What happens at the anode with aqueous solutions? - ✔✔If a halide ion is present ,
this molecule will come off. If no halide ions are present, then oxygen will be formed.
✔✔Reactivity series: - ✔✔Potassium Parrots
Sodium See
Calcium Cows
Magnesium Mooing
Aluminium And
Carbon Chewing
Zinc Zesty
Iron Indian
Tin Tinned
Lead Lemons
Hydrogen However
Copper Cats
Silver Sing
Gold Greater
Platinum Platinum records
✔✔Metals below Carbon down to hydrogen on the reactivity series can be extracted
using either... - ✔✔carbon (reduction), or electrolysis
✔✔Sulfuric acid formula - ✔✔H2SO4
✔✔The three different ions in sulfuric acud - ✔✔SO42-, H2+, OH-
✔✔What happens at the cathode during electrolysis of sulfuric acid? - ✔✔2 hydrogen
ions gain one electron each. This produces hydrogen gas. Hydrogen comes off because
sulfuric acid is more reactive
✔✔Half equation showing what happens to hydrogen ions at the cathode - ✔✔2H+ +.
2e- ---> H2
✔✔What happens at the anode during electrolysis of sulfuric acid? - ✔✔There isn't a
halogen present, so oxygen and water are produced.
✔✔How to test for hydrogen: - ✔✔Squeaky pop when presented to a lit splint
✔✔How to test for oxygen: - ✔✔Relights a glowing splint
✔✔How to test for water: - ✔✔Water or its vapour will turn cobalt
chloride paper from blue to pink
ANSWERS GRADED A+
✔✔What happens to Pb2+ at the cathode? - ✔✔a lead ion accepts/gains two electrons
to become a lead atom. (Pb)
✔✔What happens to the molten lead formed at the cathode when Pb2+ gains 2
electrons? - ✔✔it will sink to the bottom.
✔✔what is the half equation to show what happens to Pb2+ at the cathode? -
✔✔Pb2+(l) + +2e - ---> Pb(l)
✔✔Which electrode are the bromide (Br-) ions attracted to? - ✔✔the anode (positive
electrode)
✔✔what happens to Br- at the anode? - ✔✔Two bromide ions lose one electron each
and become a bromine molecule (Br2). Brown bromine gas forms at the top of the
anode.
✔✔a word to describe splitting up a compound: - ✔✔decomposing
✔✔What is the half equation to show what happens to Br- at the anode? - ✔✔2Br-(l) ----
> Br2(g) + 2e-
✔✔example of molten salts can be used for electrolysis: - ✔✔lead bromide (PbBr2)
✔✔Why don't electrodes react? - ✔✔because they are made of inert (unreactive
material)
✔✔In electrolysis of aqueous solutions, what other two ions will there be as well as the
ions from the ionic compound? - ✔✔Hydrogen ions (H+)
Hydroxide ions (OH-)
✔✔How come there are hydrogen ions and hydroxide ions in aqueous solutions but not
molten? - ✔✔Because there is water in aqueous solutions.
✔✔What happens at the cathode with aqueous solutions if the metal ions are more
reactive than the H+ ions? - ✔✔If the metal ions are more reactive than the H+ ions (e.g
sodium ions), hydrogen gas will be produced.
✔✔what happens at the cathode with aqueous solutions if the metal ions are less
reactive than the H+ ions? - ✔✔If the metal ions are less reactive than the H+ ions (e.g
copper ions), a solid layer of the pure metal will be produced instead.
, ✔✔What happens at the anode with aqueous solutions? - ✔✔If a halide ion is present ,
this molecule will come off. If no halide ions are present, then oxygen will be formed.
✔✔Reactivity series: - ✔✔Potassium Parrots
Sodium See
Calcium Cows
Magnesium Mooing
Aluminium And
Carbon Chewing
Zinc Zesty
Iron Indian
Tin Tinned
Lead Lemons
Hydrogen However
Copper Cats
Silver Sing
Gold Greater
Platinum Platinum records
✔✔Metals below Carbon down to hydrogen on the reactivity series can be extracted
using either... - ✔✔carbon (reduction), or electrolysis
✔✔Sulfuric acid formula - ✔✔H2SO4
✔✔The three different ions in sulfuric acud - ✔✔SO42-, H2+, OH-
✔✔What happens at the cathode during electrolysis of sulfuric acid? - ✔✔2 hydrogen
ions gain one electron each. This produces hydrogen gas. Hydrogen comes off because
sulfuric acid is more reactive
✔✔Half equation showing what happens to hydrogen ions at the cathode - ✔✔2H+ +.
2e- ---> H2
✔✔What happens at the anode during electrolysis of sulfuric acid? - ✔✔There isn't a
halogen present, so oxygen and water are produced.
✔✔How to test for hydrogen: - ✔✔Squeaky pop when presented to a lit splint
✔✔How to test for oxygen: - ✔✔Relights a glowing splint
✔✔How to test for water: - ✔✔Water or its vapour will turn cobalt
chloride paper from blue to pink
