Chemical Changes: Electrolysis of Aqueous Solutions
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What is an aqueous solution?
dissolved in water
What are water molecules made up of?
H+ and OH- (hydrogen and hydroxide ions)
What is the rule that tells us which ion will be is discharged at the cathode?
Hydrogen will be produced at the cathode if the metal is more reactive than hydrogen.
What metals are less reactive than hydrogen?
copper, silver, gold
What is the half equation to show hydroxide being discharged
4OH⁻ → O2 + 2H2O + 4e⁻
What will be attracted to the anode during the electrolysis of an aqueous solution?
OH⁻ and x⁻ (anion from salt)
What will be discharged at the anode if the anion in the salt is not in group 7?
OH- will discharge to form O2
What will be attracted to the cathode during tthe electrolysis of an aqueous soltuion?
H+ and x+ (cation from salt)
What will be discharged at the cathode if the cation from the salt is more reactive than hydrogen?
H+ will be discharged to form H2
What is the test and positive result for chlorine gas?
Bleaches damp blue litmus paper
What observation would indicate copper being formed
orange solid/deposit being formed
What observation would indicate a gas being produced?
bubbling/effervescence
What form of salt does the electrolyte need to be and why?
• dissolved or molten • this is because the ions are free to move and can carry a charge when molten or dissoved • when solid, the ions cannot move as there is a strong electrostatic force keeping the ions im a fixed shape or position
What is the half equation to show H+ being discharged?
2H+ + 2e- → H2
What is the half equation to show oxygen ions being discharged?
2O2- → O2 + 4e-