3.2 - Determination of formulae

Question 1

Molecular formula

Answer 1

Number of atoms of each element in a molecule

Question 2

Empirical formulae

Answer 2

Simplest whole number ratio of atoms of each element in a compound

Question 3

RMM

Answer 3

compares the mass of a molecule with the mass of an atom of carbon-12
(adding the RAM of elements thats make up the molecule)

Question 4

RFM

Answer 4

Compares the mass of a formula unit with the mass of an atom of carbon-12
(adding the RAM of elements in the empirical formula)

Question 5

Hydrated

Answer 5

When water is part of the crystalline structure

Water of crystallisation

Question 6

Blue crystals and White substance

Answer 6

Hydrated copper (II) Sulfate is heated and the bonds in the water are broken, leaving white anhydrous copper (II) sulfate

Question 7

The 2 assumptions of experimental formula

Answer 7

1) hydrous and anhydrous have different colors, you know the water is removed however if the colors are similar is more difficult because you can only see the surface of the crystal
= Heat the crystal repeatedly until the mass of the residues doesn’t change (all the water is removed)

2) Salts can decompose further when heated so it becomes more difficult to see the color change