Chemical Changes: Electrolysis of Aqueous Solutions

Question 1

What is an aqueous solution?

Answer 1

dissolved in water

Question 2

What are water molecules made up of?

Answer 2

H+ and OH-
(hydrogen and hydroxide ions)

Question 3

What is the rule that tells us which ion will be is discharged at the cathode?

Answer 3

Hydrogen will be produced at the cathode if the metal is more reactive than hydrogen.

Question 4

What metals are less reactive than hydrogen?

Answer 4

copper, silver, gold

Question 5

What is the half equation to show hydroxide being discharged

Answer 5

4OH⁻ → O₂ + 2H₂O + 4e⁻

Question 6

What will be attracted to the anode during the electrolysis of an aqueous solution?

Answer 6

OH⁻ and x⁻ (anion from salt)

Question 7

What will be discharged at the anode if the anion in the salt is not in group 7?

Answer 7

OH^- will discharge to form O₂

Question 8

What will be attracted to the cathode during tthe electrolysis of an aqueous soltuion?

Answer 8

H⁺ and x⁺ (cation from salt)

Question 9

What will be discharged at the cathode if the cation from the salt is more reactive than hydrogen?

Answer 9

H⁺ will be discharged to form H₂

Question 10

What is the test and positive result for chlorine gas?

Answer 10

Bleaches damp blue litmus paper

Question 11

What observation would indicate copper being formed

Answer 11

orange solid/deposit being formed

Question 12

What observation would indicate a gas being produced?

Answer 12

bubbling/effervescence

Question 13

What form of salt does the electrolyte need to be and why?

Answer 13

• 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

Question 14

What is the half equation to show H⁺ being discharged?

Answer 14

2H⁺ + 2e^- → H₂

Question 15

What is the half equation to show oxygen ions being discharged?

Answer 15

2O^2- → O₂ + 4e^-