formed when a substance is dissolved in water

a negatively charged electrode, in an electrolysis cell, to which the anions are attracted

a positively charged electrode, in an electrolysis cell, to which the cations are attracted

a liquid or solution that contains freely moving ions

Electrolysis of aqueous solutions

Chemistry

In the Using Earth's Resources unit, pupils learned about the extraction, production and uses of hydrocarbons from crude oil, as well as metal extraction.

This unit focuses on electrolysis, electrode reactions, and predicting products, including competing reactions in solutions. It explains metal extraction through electrolysis and writing ionic equations. It also covers tests for gases like oxygen, hydrogen, carbon dioxide, and chlorine.

Electrolysis

Which ions compete to be discharged at the cathode?

only negative ions compete; the more abundant ion is discharged

positive and negative ions compete; the ion with the highest charge is discharge

negative ions compete; the one with the lower reactivity is discharged 

positive ions compete; the ion with the lower charge is discharged

Which ions compete to be discharged at the anode, and what determines their discharge?

chlorine, because it is produced at the cathode

hydrogen, because sodium is more reactive than hydrogen

nitrogen, because it is the most abundant in the atmosphere

What gas is commonly formed at the cathode during the electrolysis of sodium chloride solution, and why?

a litmus test; the paper turns red then bleaches white

How can you test for the presence of hydrogen gas, and what is the expected result?

the reactivity of the metal compared to hydrogen

What determines whether hydrogen or a metal is produced at the cathode during electrolysis?

it bleaches it white because chlorine is a strong oxidising agent

there is no change because chlorine is inert

it turns blue because chlorine is alkaline

What is the expected result when litmus paper is exposed to chlorine gas, and why?

It is a charged particle formed by an atom gaining or losing proton.

It is a neutral particle formed by an atom gaining or losing electrons.

It is a charged particle formed by an atom gaining or losing electrons.

It is a neutral particle formed by an atom gaining or losing neutrons.

Mass can be created and destroyed, allowing for new matter.

Mass is always lost in a chemical reaction, reducing reactants.

Mass is neither created nor destroyed in a chemical reaction.

What does the law of conservation of mass state?

It is a method of mixing substances to form a solution.

It is a process that uses electric current to drive a chemical reaction.

It is a technique for measuring the mass of an element.

It is the flow of electrons in a circuit.

What is electrolysis and what is its purpose?

It is a solution in which a substance is dissolved in acid.

It is a solution in which a substance is dissolved in water.

It is a solution in which a substance is dissolved in alcohol.

It is the negatively charged electrode where reduction occurs.

It is the positively charged electrode where oxidation occurs.

What is the role of the anode in electrolysis?

What is the role of the cathode in electrolysis?

This lesson will be removed by end of Summer Term 2025.

Electrolysis of aqueous solutions

Lesson outcome

This lesson will be removed by end of Summer Term 2025.