3.1.2: Amount of Substance

Define relative atomic mass

The weighted mean mass of an atom of an element compared to one twelfth of the mass of an atom of carbon-12

Define relative isotopic mass

Mass of an atom of a specific isotope compared to 1/12 the mass of a carbon-12 atom

Define relative molecular mass (Mr)

Sum of the Ar values of the atoms in a molecule (used for simple molecules)

Define relative formula mass (Mr)

Sum of the Ar values of the atoms in one formula unit (used for ionic compounds)D

Define relative molar mass (M)

Mass of one mole of a substance in grams, numerically equal to Mr

Equations for calculating relative atomic mass

How to calculate Ar from percentage isotope abundance

How to calculate relative atomic mass from mass spectrum

Define a mole

an amount of substance containing 6.022 × 10²³ entities

What is avogadro’s constant?

The number of particles in a mole

6.022 x 10²³

What is molar mass and what are its units?

mass per mole
units: g/mol

the same numerical value as the Ar/Mr

Equation for moles

moles = mass/ Mr

Equation linking moles, concentration, volume

moles = conc x vol