Mole Concept and Stoichiometry

Relative Masses (no units, 1dp)

Relative Atomic Mass (Ar)

Relative Isotopic Mass

Relative Molecular Mass (Mr)

Relative Formula Mass (Mr)

Definition

RMM of a molecule is the ratio of the average mass of one molecule to 1/12 the mass of an atom of carbon-12

Definition

RAM of an element is the ratio of the average mass of one atom of that element to 1/12 the mass of an atom of carbon-12

Found in the Periodic Table (the mass number)

Definition

RIM of a particular isotope is the ratio of the mass of one atom of that isotope to 1/12 the mass of an atom of carbon-12.

Definition

RFM of an ionic compound is the ratio of the average mass of one formula unit of that compound to 1/12 the mass of an atom of carbon-12

The mole

Definition

A measure for the amount of substance, which is equal to 6.02x10^23 [particles / elementary entities]. (6.02x10^23 is Avogadro's Constant)

One mole of (element/compound) has a mass of exactly (Ar/Mr)g. Eg: 1 mol of Cl has a mass of 35.5g

Calculations

Relationship between Amount, Number of Particles, Mass and Molar Mass

Empirical and Molecular Formulae

Empirical Formula

Molecular Formula

Definition

A formula of a compound that shows the simplest ratio of each type of atoms in a compound

Definition

A formula of a compound that shows the actual number of atoms in a compound

Relationship

Determination

Determination

Stoichiometry of Gases

Avogadro's Law

Law: Equal volumes of all gases contain the same number of particles at the same temperature and pressure.

Molar Volume

The volume occupied by 1 mol of gas

stp: 22.7 dm3mol-1

rtp: 24.0 dm3mol-1

Implied: When 2 gases are measured at same t & p, Mole ratio = Volume Ratio

Stoichiometry of Gases

Limiting Reagent

The one that is completely used up in the reaction.

Percentages

Percentage Composition by Mass: Fig 3 of https://tinyurl.com/ChemIP3

Percentage Yield: Fig 4 of https://tinyurl.com/ChemIP3

Percentage Purity: Fig 5 of https://tinyurl.com/ChemIP3

Concentrations

Determines the amount of products formed

Calculation Approach: Fig 6 of https://tinyurl.com/ChemIP3