Amount of substance (mass). Flashcards
Amount of substance definition.
(n)- the quantity used to count the number of particles in a substance.
Mole (mol) definition.
What amount of substance is measured in. 1 mole is the amount of substance that contains 6.02 x 10^23 particles.
Avogadro’s constant.
6.02 x 10^23 mol ^-1. The number of particles in each mole of carbon-12.
Molar mass definition.
The mass in grams in each mole of the substance/mass per mole of substance (g mol ^-1).
Moles equation.
Mass / Mr = moles.
Molecular formula definition.
The number and type of atoms of each element in a specific molecule.
Empirical formula definition.
The simplest whole number ratio of atoms of each element in a compound.
Hydrated salt definition.
Coloured crystals that are hydrated and water molecules are part of their crystalline structure.
Water of crystallisation definition.
Water molecules that are in hydrated salts.
Anhydrous salts definition.
When a hydrated salt is heated, bonds holding water in the crystal are broken and water is driven off=anhydrous salt.
emp form and mol form.
Practise exam questions.
Magnesium oxide practical (PAG 1.3).
1) Measure mass of crucible and lid.
2)Put Mg ribbon into crucible (coil so fits) and reweigh contents and crucible and lid.
3)Put crucible on clay pipe triangle on Bunsen and heat strongly. Raise lid with tongs slightly to control reaction.
4)When reaction nearly complete, place lid on heat-proof mat and heat crucible strongly for 5 mins. During, tap MgO gently with tongs to break up residue and expose any Mg that has not reacted/ was covered/inside.
5) Allow crucible to cool and reweigh all.
6)Calculate formula and write balanced equation.
Relative molecular mass(Mr) definition.
The weighted mean mass of a molecule of a compound compared with 1/12th of the mass of an atom of carbon-12.
Relative formula mass definition.
The weighted mean mass of the formula unit of a compound compared with the 1/12th of the mass of an atom of carbon-12.
Amount of substance definition.
The quantity, whose unit of the mole, used as a means of counting any species such as atoms, ions and molecules.
