Electrolysis (Cambridge (CIE) IGCSE Chemistry)

Molten lead is produced at the cathode during electrolysis of molten lead(II) bromide.

Brown fumes of bromine gas are produced at the anode during electrolysis of molten lead(II) bromide.

The products of electrolysis of molten zinc chloride would be zinc at the cathode and chlorine at the anode.

Graphite or platinum electrodes are typically used in the electrolysis of molten compounds.

Molten ionic compounds conduct electricity because their ions can move freely and carry the current.

Two chloride ions are attracted to the anode where they each lose one electron.

They bond to form a molecule of chlorine.

2Cl^- ⟶ Cl₂ + 2e^-

True.

The positive ion will migrate towards the cathode and the negative ion will migrate towards the anode.

False.

The cathode product will always be the metal l and the product formed at the anode will always be the non-metal.

Brine is a concentrated solution of aqueous sodium chloride.

The products of the electrolysis of brine are chlorine gas, hydrogen gas, and sodium hydroxide solution.

False.

During the electrolysis of brine, hydrogen ions are discharged at the cathode, not sodium ions.

Chlorine gas is produced at the anode during the electrolysis of brine.

In the electrolysis of dilute sulfuric acid, hydrogen gas is produced at the cathode.

Oxygen gas is produced at the anode during the electrolysis of dilute sulfuric acid.

True.

The volume of hydrogen produced is twice that of oxygen in the electrolysis of dilute sulfuric acid.

The test for oxygen gas is that a glowing splint will relight when dipped into a sample of the gas.

Hydrogen gas is tested for by dipping a lit splint into a sample of the gas, which will produce a squeaky pop.

The test for chlorine gas is that damp litmus paper will turn red and then bleach to a white colour when dipped into a sample of the gas.

Aqueous solutions always have H⁺ and OH^- ions present from the splitting of water molecules.

False.

Concentrated and dilute solutions of the same compound can give different products during electrolysis.

The relative reactivity of the elements involved determines which ions are discharged at the electrodes during electrolysis of aqueous solutions.

In the electrolysis of concentrated copper(II) chloride solution, chlorine is produced at the anode.

Oxygen is produced at the anode during the electrolysis of dilute halide solutions.

False.

For metals above hydrogen in the reactivity series, hydrogen gas will be produced at the cathode instead of the metal.

Copper metal is produced at the cathode during the electrolysis of aqueous copper sulfate.

In the electrolysis of aqueous copper sulfate with copper electrodes, the anode decreases in mass.

Oxygen gas is produced at the anode during the electrolysis of dilute sulfuric acid.

Negatively charged OH^- ions and non-metal ions are attracted to the positive electrode.

H⁺ ions and metal ions are attracted to the negative electrode.

The product at the cathode is determined by the position of the metal in the reactivity series relative to hydrogen.

Hydrogen gas is produced at the cathode during electrolysis of sodium chloride solution.

Oxidation is the loss of electrons.

Reduction is the gain of electrons.

False.

Oxidation occurs at the anode during electrolysis.

The ionic half-equation for the reduction of copper(II) ions is:

Cu²⁺ + 2e^- → Cu

The ionic half-equation for the oxidation of chloride ions is:

2Cl^- → Cl₂ + 2e^-

The ionic half-equation for the reduction of hydrogen ions is:

2H⁺ + 2e^- → H₂

The ionic half- equation for the reduction of Sn²⁺ ions is:

Sn²⁺ + 2e^- → Sn

The ionic half-equation for the reduction of Pb²⁺ ions at the cathode is:

Pb²⁺ + 2e^- → Pb

True.

In ionic half-equations, the charges on each side of the equation should always balance.

The balanced ionic half-equation for the oxidation of water molecules at the anode in acidic solutions is:

2H₂O → O₂ + 4H⁺ + 4e^-