In 2CuO + C → 2Cu + CO₂, state which substance is oxidised and which is reduced.

Carbon is oxidised because it gains oxygen, and copper oxide is reduced because it loses oxygen.

What is an oxidising agent?

A substance that oxidises another substance by giving oxygen to it, and is itself reduced.

What is a reducing agent?

A substance that reduces another substance by taking oxygen away from it, and is itself oxidised.

In Fe₂O₃ + 3CO → 2Fe + 3CO₂, name the reducing agent and explain your choice.

Carbon monoxide, because it removes oxygen from the iron oxide and is itself oxidised to carbon dioxide.

OCR GCSE Combined Science Chemistry J250

Chemical Reactions

Topic overview Writing formulae of elements and compounds Balanced equations, and deducing formulae from ions State symbols in equations Conservation of mass, and changes of mass in open systems Exothermic and endothermic reactions, and reaction profiles Activation energy and why reactions need it Oxidation and reduction in terms of oxygen Acids, alkalis and neutralisation The ionic equation for neutralisation, and reactions of acids The pH scale, acidity and alkalinity Measuring pH with indicators and pH meters 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 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 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 Activation energy, and enzymes as catalysts

Particles

Topic overview The particle model and changes of state 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

Oxidation and reduction in terms of oxygen

3 things to know
Paper 3 (Chemistry)

Overview

Oxidation and reduction as the gain and loss of oxygen, identifying what is oxidised and reduced when carbon reduces copper oxide, oxidising and reducing agents, carbon monoxide as the reducing agent for iron oxide, magnesium burning in air, and why oxidation and reduction always happen together.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

In terms of oxygen, explain what a reducing agent is, name the reducing agent in Fe₂O₃ + 3CO → 2Fe + 3CO₂, say whether magnesium burning in air is oxidised or reduced, and why oxidation and reduction always happen together.

Key term

Define oxidation in terms of oxygen.

Key term

Define reduction in terms of oxygen.

Questions from this subtopic

Each one with the model answer underneath.

1
Define oxidation in terms of oxygen.
Model answer
Oxidation is the gain of oxygen by a substance.
2
Define reduction in terms of oxygen.
Model answer
Reduction is the loss of oxygen from a substance.
3
In 2CuO + C → 2Cu + CO₂, state which substance is oxidised and which is reduced.
Model answer
Carbon is oxidised because it gains oxygen, and copper oxide is reduced because it loses oxygen.
4
What is an oxidising agent?
Model answer
A substance that oxidises another substance by giving oxygen to it, and is itself reduced.
5
What is a reducing agent?
Model answer
A substance that reduces another substance by taking oxygen away from it, and is itself oxidised.
6
In Fe₂O₃ + 3CO → 2Fe + 3CO₂, name the reducing agent and explain your choice.
Model answer
Carbon monoxide, because it removes oxygen from the iron oxide and is itself oxidised to carbon dioxide.

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Chemical Reactions

Elements, Compounds and Mixtures

Global Challenges

Monitoring and Controlling Chemical Reactions

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BKI, because potassium loses one electron and iodine gains one.

CCaCl₂, because a calcium atom loses two electrons and each chlorine atom gains one.

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