Chemistry Acids, Bases & Salts Revision Flashcards

Comprehensive vocabulary flashcards covering the definitions, indicators, pH scale concepts, and chemical compounds from the Acids, Bases & Salts chemistry lecture nodes.

Indicator

A substance that tells whether another substance is acidic or basic in nature by a change in colour.

Olfactory Indicators

Substances whose odour changes in acidic or basic media, such as onion, vanilla, and clove oil.

Neutralisation

The reaction between an acid and a base to form salt and water.

Acid

A substance which dissociates or ionises when dissolved in water to release hydrogen ions ($H^+$).

Hydronium ions

Ions formed when hydrogen ions ($H^+$) combine with polar water molecules, represented as $H_3O^+$.

Base

A substance which dissolves in water to produce hydroxide ions ($OH^-$).

Alkalis

Bases which are soluble in water.

pH of a solution

The negative logarithm to the base 10 of the hydrogen ion concentration expressed in mole per litre: $pH = -\text{log}_{10}(H^+)$.

pH scale

A scale ranging from 0 to 14 showing the relative strength of acids and alkalis; $pH = 7$ is neutral, less than 7 is acidic, and more than 7 is basic.

Universal Indicator

A mixture of several indicators that shows different colours at different concentrations of hydrogen ions in a solution.

Acid rain

Rain water with a pH of less than $5.6$.

Antacids

A group of mild bases, such as magnesium hydroxide ($Mg(OH)_2$) or sodium bicarbonate ($NaHCO_3$), used to neutralise excess stomach acid.

Tooth enamel

The hardest substance in the body, made of calcium phosphate, which corrodes when the pH in the mouth falls below $5.5$.

Family of salts

Salts having the same positive ions or the same negative ions.

Common Salt

Sodium chloride ($NaCl$), a neutral salt prepared by the reaction of sodium hydroxide and hydrochloric acid.

Brine

An aqueous solution of sodium chloride used in the electrolysis for the chlor-alkali process.

Chlor-alkali process

The electrolysis of brine that produces sodium hydroxide ($NaOH$), chlorine ($Cl_2$), and hydrogen ($H_2$).

Bleaching Powder

A substance represented as $CaOCl_2$, produced by the action of chlorine gas on dry slaked lime ($Ca(OH)_2$).

Baking Soda

Sodium hydrogen carbonate ($NaHCO_3$), used as an antacid, to make baking powder, and in soda-acid fire extinguishers.

Washing Soda

Sodium carbonate decahydrate ($Na_2CO_3 \times 10H_2O$), produced by the re-crystallisation of sodium carbonate.

Water Of Crystallisation

The water molecules which form a part of the structure of a crystal.

Hydrated salts

Salts that contain a fixed number of molecules of water of crystallisation in their formula unit, such as $CuSO_4 \times 5H_2O$.

Plaster of Paris

Calcium sulphate hemihydrate ($CaSO_4 \times \frac{1}{2}H_2O$), prepared by heating gypsum at $373\text{ K}$.

Gypsum

The starting material ($CaSO_4 \times 2H_2O$) used to manufacture Plaster of Paris.