What decides which product forms at the anode in an aqueous solution?

Oxygen is produced unless a halide ion is present, in which case the halogen is released instead.

Name the products of the electrolysis of sodium chloride solution using inert electrodes.

Hydrogen at the cathode and chlorine at the anode.

Why is sodium not produced when sodium chloride solution is electrolysed?

Sodium is more reactive than hydrogen, so the hydrogen ions from the water gain the electrons instead.

Name the products of the electrolysis of copper(II) sulfate solution using inert electrodes.

Copper at the cathode and oxygen at the anode.

OCR GCSE Combined Science Chemistry J250

Chemical Reactions

Topic overview Writing formulae of elements and compounds Balanced equations, and deducing formulae from ions Ionic equations, and state symbols The mole and the Avogadro constant Conservation of mass, and changes of mass in open systems Stoichiometry, and calculating reacting masses Exothermic and endothermic reactions, and reaction profiles Activation energy, and bond energy calculations Oxidation and reduction, by oxygen and by electrons Acids, alkalis and neutralisation The ionic equation for neutralisation, and reactions of acids Dilute and concentrated, weak and strong The pH scale, and hydrogen ion concentration pH as a factor of ten, and measuring pH Products at the electrodes, and molten ionic compounds Electrolysis of aqueous solutions Inert and non-inert electrodes

Elements, Compounds and Mixtures

Topic overview Purity, and melting point data Relative formula mass and empirical formulae Formulations, and separating mixtures Paper and thin layer chromatography Interpreting chromatograms and Rf values Choosing a purification method Metals and non-metals in the Periodic Table Electron arrangement and position in the Periodic Table Ionic, covalent and metallic bonding compared Dot and cross diagrams, and the limits of models Reactions, electron arrangement and Mendeleev's table Carbon's four bonds, and the variety of organic compounds Diamond, graphite, fullerenes and graphene Bond strength, intermolecular forces and predicting state Bulk properties of ionic, molecular and giant structures

Global Challenges

Topic overview Extracting metals by reduction and by electrolysis Biological methods of metal extraction Life cycle assessment Recycling, and the decisions behind it Fractional distillation of crude oil The fractions, and crude oil as a feedstock Dependence on hydrocarbons, and cracking The Earth's early atmosphere, and how oxygen developed The greenhouse effect, and evidence for climate change Effects of carbon dioxide and methane, and air pollutants Producing potable water

Monitoring and Controlling Chemical Reactions

Topic overview Mass of solute, concentration and dilution calculations Measuring the rate of a reaction, and rate graphs Factors affecting rate, and collision theory Surface area and rate Catalysts and how they work Reversible reactions and dynamic equilibrium Changing the conditions of an equilibrium Activation energy, and enzymes as catalysts

Particles

Topic overview The particle model and changes of state Limitations of the particle model How the atomic model changed, and the structure of the atom The size of atoms, and the subatomic particles Calculating protons, neutrons and electrons

Predicting and Identifying Reactions

Topic overview Groups 1, 7 and 0, and why they behave as they do Predicting reactivity from the Periodic Table Reactivity of metals with water and acids Tests for oxygen, hydrogen, carbon dioxide and chlorine

Chemical Reactions

Electrolysis of aqueous solutions

2 things to know
Paper 9 (Chemistry)

Overview

The hydrogen and hydroxide ions from water, the rules for what forms at each electrode, the products from sodium chloride and copper(II) sulfate solutions, and the half equations for hydrogen, chlorine, oxygen and copper.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Which extra ions are present in any aqueous solution besides those of the dissolved compound?

Key term

What decides whether a metal or hydrogen is produced at the cathode in an aqueous solution?

Questions from this subtopic

Each one with the model answer underneath.

1
Which extra ions are present in any aqueous solution besides those of the dissolved compound?
Model answer
Hydrogen ions and hydroxide ions, which come from the water itself.
2
What decides whether a metal or hydrogen is produced at the cathode in an aqueous solution?
Model answer
Hydrogen is produced unless the metal is less reactive than hydrogen, in which case the metal is deposited.
3
What decides which product forms at the anode in an aqueous solution?
Model answer
Oxygen is produced unless a halide ion is present, in which case the halogen is released instead.
4
Name the products of the electrolysis of sodium chloride solution using inert electrodes.
Model answer
Hydrogen at the cathode and chlorine at the anode.
5
Why is sodium not produced when sodium chloride solution is electrolysed?
Model answer
Sodium is more reactive than hydrogen, so the hydrogen ions from the water gain the electrons instead.
6
Name the products of the electrolysis of copper(II) sulfate solution using inert electrodes.
Model answer
Copper at the cathode and oxygen at the anode.

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Chemical Reactions

Elements, Compounds and Mixtures

Global Challenges

Monitoring and Controlling Chemical Reactions

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