IGCSE Chemistry - Formulae, Equations, Redox, Acids, Bases and Salts

Flashcards covering key vocabulary and concepts from the IGCSE Chemistry lecture notes on formulae, equations, redox reactions, acids, bases, and salts.

Empirical Formula

The simplest whole number ratio of the atoms of each element present in one molecule or formula unit of the compound.

Polyatomic Ions

Ionic compounds that contain more than one atom.

Charge Neutrality in Ionic Compounds

Ionic compounds typically have no overall charge because the positive and negative charges of the ions cancel each other out.

Swap-and-Drop Method

A method to determine the formulae of ionic compounds by swapping the charges of the ions and dropping them down as subscripts.

Word Equations

Show the reactants and products of a chemical reaction using their full chemical names.

Symbol Equations

Use the formulae of the reactants and products to show what happens in a chemical reaction.

State Symbols

Solid (s), Liquid (l), Gas (g), Aqueous (aq)

Oxidation Number

The number assigned to an atom or ion in a compound that shows the number of electrons that an atom has lost, gained, or shared in forming a compound.

Oxidizing Agent

A substance that oxidizes another substance and becomes reduced in the process; it gains electrons.

Reducing Agent

A substance that reduces another substance and becomes oxidized in the process; it loses electrons.

Acids

Substances that can neutralise a base, forming a salt and water.

Ions in Acids and Bases

Acids are a source of hydrogen ions, H+ , and bases (or alkalis) are a source of hydroxide ions, OH- .

Reaction between Acid and Base

A salt and water are produced.

Acidic pH

A pH value below 7.

Alkaline pH

A pH value above 7.

Indicators in Bases/Alkali Conditions

In basic (alkaline) conditions red litmus paper turns blue, methyl orange indicator turns yellow, and thymolphthalein indicator turns blue.

Strong Acid

An acid with a low pH.

Weak Acid

An acid with a pH closer to the middle of the scale.

Oxides

Are compounds made from one or more atoms of oxygen combined with one other element.

Acidic Oxides

Oxides are formed when a non-metal element combines with oxygen. They react with bases to form a salt and water and produce an acidic solution with a low pH when dissolved in water.

Basic Oxides

Oxides are formed when a metal element combines with oxygen. They react with acids to form a salt and water and produce a basic solution with a high pH when dissolved in water.

Neutral Oxides

Some oxides do not react with either acids or bases.

Amphoteric Oxides

Oxides are a curious group of oxides that can behave as both acidic and basic, depending on whether the other reactant is an acid or a base.

Salt

A compound that is formed when the hydrogen atom in an acid is replaced by a metal.

Anhydrous Salts

Are those that contain no water in their structure

Hydrated Salts

Salts that contain water within their structure.

Water of Crystallization

Occurs within the structure of some salts during the crystallization process known as

Measuring Cylinders

Are used when approximate volumes are required (accuracy is not an important factor).

Solvent

The liquid in which a solute dissolves.

Solute

The substance which dissolves in a liquid to form a solution.

Titrations

Determines exactly how much alkali is needed to neutralize a quantity of acid – and vice versa.