Chemistry GCSE AQA Year 9: Acids, Bases and Salts

What can acids be neutralised by?

. Alkalis (e.g soluble metal hydroxides)

. Bases (e.g insoluble metal hydroxides and metal oxides)

. Metal carbonates

Acid + metal →

salt + hydrogen

Acid + metal oxide →

salt + water

Acid + metal carbonate →

Salt + Water + Carbon dioxide

What type of salt does nitric acid produce?

nitrate

What type of salt does sulfuric acid produce?

sulfate

What type of salt does hydrochloric acid produce?

chloride

What is the formula for hydrochloric acid?

HCl (aq)

What is the formula for sulfuric acid?

H₂SO₄ (aq)

What is the formula for nitric acid?

HNO₃ (aq)

How can soluble salts be made from acids?

. By reacting them with solid insoluble substances, such as metals, metal oxides, hydroxides, or carbonates

. The solid is added to the acid until no more reacts and the excess solid is filtered off to produce a solution of the salt

. Salt solutions can be crystallised to produce solid salts

What is a salt?

. Product of neutralisation

. Formed from metal of base and everything in acid except H⁺ ion

What is the pH scale?

. From 0 to 14

. A measure of the acidity or alkalinity of a solution

. Can be measured using universal indicator or a pH probe

What are acids?

. Produce H⁺ ions in aqueous solutions

. Aqueous solutions of acids have pH values of less than 7

What are alkalis?

. Aqueous solutions of alkalis contain hydroxide ions (OH-)

. Aqueous solutions of alkalis have pH values greater than 7

. (A base that dissolves in water)

. Any group 1 hydroxide is an alkali

What is a base?

. A substance that neutralises an acid

. Generally is (or contains) a metal

What is a solution with pH 7?

neutral

What is the symbol equation for what happens to hydrogen ions and hydroxide ions in neutralisation reactions between acids and alkalis?

H⁺ (aq) + OH⁻ (aq) → H₂O (l)

What is a strong acid?

An acid that is completely ionised in aqueous solution

What are examples of strong acids?

. Hydrochloric

. Nitric

. Sulfuric

What is a weak acid?

An acid that is only partially ionised in aqueous solution

What are examples of weak acids?

. Ethanoic

. Citric

. Carbonic

How is pH affected by the strength of acids?

. For a given concentration of aqueous solutions, the stronger the acid, the lower the pH

. As the pH decreases by one unit, the hydrogen ion concentration of the solution increases by a factor of 10

What is the concentration of a solution?

. A measure of the mass or amount of solute dissolved in a given volume of solvent or solution

. Opposite of concentrated is dilute

How does the concentration of an acid affect its pH?

The more concentrated the acid the lower the pH