IGCSE CHEM CHAP 7: ACIDS & BASES

Acid

A chemical which can neutralise bases, acids have a pH value less than 7 and contains H+ ions.

Acids

They are proton donors.

Acidic oxide

This compound is formed when a non-metal reacts with oxygen. It produces an acid when reacted with water.

Alkali

It is a base that is soluble (dissolve in aqueous solutions to release hydrogen ions OH ions).

Amphoteric

This compound is able to act as an acid and a base.

Amphoteric oxide

This compound reacts with acids and bases to produce a salt and water.

Anhydrous substance

a substance that does not contain water.

Base

A chemical which reacts with acids in neutralisation reactions.

Bases

They are proton acceptors.

Basic oxide

This compound is formed when a metal reacts with oxygen.It produces a base when reacted with water.

Hydrated substance

a substance that is chemically combined with water

Litmus

A chemical dye which is used to identify acids and bases. The dye is red in the presence of an acid and blue in the presence of a base.

Methyl orange

A chemical indicator which is used to identify acids and bases. The indicator is red in acids and yellow in bases.

Neutralisation

The reaction in which an acid and a base react together to form a salt and water.

pH scale

A measure of the acidity or alkalinity of a solution. The scale ranges from 0-14 and can be measured using universal indicator or a pH probe.

Precipitation reaction

A reaction in which solutions react to form an insoluble product.

Strong acid

This compound is completely ionised in an aqueous solution so that nearly all the H+ ions are released.

Universal indicator

A mixture of dyes that changes colour gradually over a range of pH and is used in testing for acids and alkalis.

Water of crystallisation

This term refers to the water molecules that are present in hydrated crystals.

Weak acid

This compound is only partially ionised in an aqueous solution. This means only a small number of the H+ ions are released.

Ethanoic, citric and carbonic acids

Examples of weak acids

Salt and hydrogen

What are the products when a dilute acid reacts with a metal?

Salt and water

What are the products when an acid reacts with a metal oxide?

Salt and water

What are the products when an acid reacts with a metal hydroxide?

Salt, water and carbon dioxide

What are the products when an acid reacts with a metal carbonate?

HCl + NH3 → NH4Cl

Chemical equation for hydrochloric acid and ammonia

H2SO4 + 2NaOH → Na2SO4 + 2H2O

Chemical equation for sulfuric acid and sodium hydroxide

NH4Cl (s) + KOH (aq) → KCl (aq) + H2O (l) + NH3 (g)

Chemical equation for ammonium chloride and potassium hydroxide

Acid - Turns red
Alkali - Stays blue

What colour is blue litmus paper in acid and alkali?

Acid - Stays red
Alkali - Turns blue

What colour is red litmus paper in acid and alkali?

Bases are oxides and hydroxides of metals Alkalis are bases that are soluble (dissolve in aqueous solution)

What is the difference between a base and an alkali?