Chemistry 2.2 Acids, Bases and Salts

What is an acidic solution

A solution with pH less than 7 and the lower the pH the stronger the acid

What is an alkaline solution

A solution with pH more than 7 the higher the pH the stronger the alkali and an alkali is a base dissolved in water

pH of a neutral solution

pH 7

Ions in acids

Hydrogen ions H+

Ions in alkalis

Hydroxide ions OH-

Strong acid

An acid that completely dissociates to release H+ ions in aqueous solution

Weak acid

An acid that partially dissociates to release H+ ions in aqueous solution

Strong base

A base that completely dissociates to release OH- ions in aqueous solution

Weak base

A base that partially dissociates to release OH- ions in aqueous solution

Metal plus dilute acid products

Acid + Metal -> Salt + Hydrogen

Generally, the more reactive the metal in the reactivity series, the faster the reaction

Neutralisation reactions of acids

Acid + alkali → salt + water

Acid + base → salt + water

Acid + metal carbonate → salt water + carbon dioxide

Neutralisation

Reaction of H+ ions with OH- ions to form H₂O

Test for carbonates

Add dilute acid and bubble the gas through limewater if it turns cloudy carbon dioxide is present

Preparing crystals of soluble salts

Neutralise acid with excess base filter evaporate solution and allow crystals to form

Preparing soluble salts

React an acid with an insoluble metal metal oxide hydroxide or carbonate

Salts from acids

Hydrochloric acid makes chlorides nitric acid makes nitrates sulfuric acid makes sulfates

Test for sulfate ions

Add dilute hydrochloric acid then barium chloride a white precipitate forms

Titration

A method to prepare soluble salts and determine concentrations of acids and alkalis

Calculating concentration

Concentration = moles ÷ volume

Units are mol dm^-3

Concentration of an acid or base

The number of moles of acid or base in solution

Strength of an acid or base

How easily it ionises and releases H+ or OH- ions

Preparing insoluble salts

Use precipitation react two solutions filter wash and dry the precipitate