Chemical Changes: Reactions of Acids

Acids: Substances that contain hydrogen ions (H+).
Strong Acid versus Weak Acid: The strength of an acid is not about its concentration (how much acid there is in a volume). Rather, it’s about how much it ionises in water. Strong acids, like hydrochloric acid, fully ionise - meaning more hydrogen ions are in the solution. Weak acids, like ethanoic acid, only partially ionise meaning less hydrogen ions are released.
pH of a solution: The acidity or alkalinity of a solution is measured by its pH. Stronger acids have a lower pH than weaker acids.
Reactions of Acids with Metals: An acid reacts with a metal to produce a salt and hydrogen. This is a redox reaction involving the transfer of electrons.
Reactions of Acids with Bases: An acid reacts with a base to produce a salt and water. This is termed a neutralisation reaction. Bases are substances that can neutralise an acid; examples include metal oxides and hydroxides, and ammonia.
Reactions of Acids with Carbonates: An acid reacts with a carbonate to produce a salt, water, and carbon dioxide. This is a two-part reaction involving acid reacting with carbonate to form a salt and carbonic acid, and carbonic acid further breaking down into water and carbon dioxide.
Making Salts: Different methods are used to make salts, including reaction with a base or carbonate. Precipitation reactions can also be used when two solutions react together to form an insoluble solid.
Oxidation and Reduction: Redox reactions involve the transfer of electrons. Oxidation is a gain of oxygen, a loss of hydrogen, or a loss of electrons. Reduction is a loss of oxygen, a gain of hydrogen, or a gain of electrons.
Electrolysis: The process of breaking down ionic substances into simpler substances using electricity is called electrolysis. It requires a substance to be melted or dissolved in water to make a free-moving ions which can conduct electricity and allow a current to flow.
Basic Rules for Naming Salts: The name of the salt formed in a reaction depends on the metal in the base and the acid used. For example, salts made from hydrochloric acid are chlorides, with sulfuric acid are sulphates, and with nitric acid are nitrates.