Quick Revision

Need some help with quick revision of key concepts?

We’ve put together some packs of study cards to help you brush up on key concepts before tests and exams. Use the drop down menus in the search boxes above to select the grade, subject and category of content you want to revise. We’re adding new packs of study cards all the time, so check back if you can’t find what you’re looking for or contact us to make a suggestion.

Grade
Subject
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Grade 12 Physical Sciences, Chemical change

In a fuel cell, what is the anode?

Grade 12 Physical Sciences, Chemical change

The anode of a fuel cell refers to the electrode at which oxidation occurs.

Grade 12 Physical Sciences, Chemical change

Explain an auto-redox reaction in terms of hydrogen peroxide.

Grade 12 Physical Sciences, Chemical change

Hydrogen peroxide spontaneously reacts to form water and oxygen. One molecule of hydrogen peroxide acts as the reducing agent and one molecule acts as the oxidising agent.

Grade 12 Physical Sciences, Chemical change

What is the role of a catalyst in a reaction?

Grade 12 Physical Sciences, Chemical change

A catalyst is a substance that takes part in a reaction but that is not used up. The catalyst increases the rate of the reaction by providing an alternative pathway.

Grade 12 Physical Sciences, Chemical change

When is a dynamic equilibrium achieved in a system?

Grade 12 Physical Sciences, Chemical change

A dynamic equilibrium occurs when the rate of the forward reaction equals the rate of the reverse reaction.

Grade 12 Physical Sciences, Chemical change

What is an electrolyte?

Grade 12 Physical Sciences, Chemical change

An electrolyte is a substance that dissolves in water to produce a solution that conducts an electric current.

Grade 12 Physical Sciences, Chemical change

Explain what happens during an electron transfer reaction.

Grade 12 Physical Sciences, Chemical change

During an electron transfer reaction, one reactant loses electrons and another gains electrons.

Grade 12 Physical Sciences, Chemical change

What is the equation for the equilibrium constant?

Grade 12 Physical Sciences, Chemical change
Grade 12 Physical Sciences, Chemical change

Explain the difference between forward reactions and reverse reactions.

Grade 12 Physical Sciences, Chemical change

During a forward reaction, reactants are used up and products are formed. During a reverse reaction, the products are used up and reactants are formed.

Grade 12 Physical Sciences, Chemical change

What are galvanic cells?

Grade 12 Physical Sciences, Chemical change

Galvanic cells are electrochemical cells. Galvanic cells generate a voltage across their terminals. They are a source of energy and do not need an external potential difference like electrolytic cells.

Grade 12 Physical Sciences, Chemical change

Define half-cells.

Grade 12 Physical Sciences, Chemical change

An electrochemical cell has two half cells. Each half cell has an electrode. One half cell is the seat of oxidation. The other half is the seat of reduction.

Grade 12 Physical Sciences, Chemical change

State Le Chatelier's principle.

Grade 12 Physical Sciences, Chemical change

Le Chatelier's principle states that if we increase the temperature/pressure/concentration of a substance, there is a shift to decrease the temperature/pressure/concentration of the substance.

Grade 12 Physical Sciences, Chemical change

In a reaction, what is the limiting reagent?

Grade 12 Physical Sciences, Chemical change

The limiting reagent will stop the reaction when it is used up. In a reaction, if one reactant is available in excess, the other reactant will be the limiting reagent.

Grade 12 Physical Sciences, Chemical change

What does the rate of the reaction refer to?

Grade 12 Physical Sciences, Chemical change

The rate of the reaction tells us how fast the reaction occurs.

Grade 12 Physical Sciences, Chemical change

How do we find the reaction quotient?

Grade 12 Physical Sciences, Chemical change

The reaction quotient is the ratio of products to reactants.

Grade 12 Physical Sciences, Chemical change

What is the reaction quotient at equilibrium?

Grade 12 Physical Sciences, Chemical change

At equilibrium the reaction quotient equals the equilibrium constant.

Grade 12 Physical Sciences, Chemical change

Why do we use the word redox for redox reactions?

Grade 12 Physical Sciences, Chemical change

Redox is a combination of reduction and oxidation. A redox reaction consists of two half-reactions, namely a oxidation and a simultaneous reduction.

Grade 12 Physical Sciences, Chemical change

Define a saturated solution and give an example.

Grade 12 Physical Sciences, Chemical change

In a saturated solution you cannot dissolve any more of a solid. If we add sodium chloride to water until no more will dissolve, the resultant solution is saturated.

Grade 12 Physical Sciences, Chemical change

In a reaction, what is a spectator ion?

Grade 12 Physical Sciences, Chemical change

A spectator ion is present in the reaction mixture throughout but the ion does not take part in the reaction.

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