2.3 - Electrolysis of Aqueous Solutions

What ions are contained in solution?

H+, OH-

What does the ions discharged at each electrode depend on?

the reactivity of the elements involved

What happens in the Electrolysis of Aqueous Solutions at the cathode?

H₂ produced unless the metal is less reactive than hydrogen

What happens in the electrolysis of Aqueous Solutions at the anode?

O₂ produced unless solution contains halide ions

What happens in the electrolysis of lead sulphate solution at the cathode?

• Pb²⁺ and H+ both attracted to cathode

• H+ less active so hydrogen gas forms

What is the equation for the electrolysis of lead sulphate solution at the cathode?

2H+_(aq) + 2e- →H_2(g)

What happens in the electrolysis of lead sulphate solution at the anode?

OH- and SO₄^-2 both attracted to anode oxygen gas is formed (no halide ions present)

What is the equation for the electrolysis of lead sulphate solution at the anode?

• 4OH-_(aq) → O_2(g) + 2H₂O_(l) + 4e-

• 4OH-_(aq) - 4e- → O_2(g) + 2H₂O_(l)

What is brine?

concentrated sodium chloride solution

What happens in the electrolysis of brine at the cathode?

• H+ and Na+ are both attracted to the cathode

• H+ gains an electrons forming hydrogen atoms

• 2 hydrogen atoms bond to form hydrogen gas

What is the equation for the electrolysis of brine at the cathode?

2H+_(aq) + 2e^- → H_2(g)

What happens in the electrolysis of brine at the anode?

• OH- and Cl- are both attracted to the anode

• Cl- loses an electron to form chlorine atoms (oxidation

• Two chlorine atoms bond to form chlorine gas

What is the equation for the electrolysis of brine at the anode?

• 2Cl^-_(aq) - 2e^- → Cl_2(g)

• 2Cl^-_{(aq) →} Cl_{2(g) +} 2e^-

What happens to the remaining Na+ and OH- in brine after electrolysis?

they remain dissolved in solution and bond forming sodium hydroxide

What is H₂ used for?

• make HCl

• alternative fuel

What is Cl₂ used for?

• make bleach

• kill bacteria

What is NaOH used for?

• make bleach

• make paper