Section Two: Formulas And Equations

Question 1

define the empirical formula and the molecular formula

Answer 1

empirical: Simplest whole number ratio of atoms of each element present in a compound

molecular: actual number of atoms of each type of element in a molecule

Question 2

how do you calculate the molecular formula if you know the emperical formula and the molecular mass of a compound?

Answer 2

1. find empirical mass (relative atomic mass values of all atoms in empirical formula)
2. divide molecular mass by the empirical mass, this gives you the number of empirical units in the molecule
3. multiply the empirical formula by the no. of empirical units in the molecule

Question 3

how do you calculate the empirical formula from experimental data?

Question 4

how do you work out then empirical formula from percentage compositions?

Question 5

how do you work out the molecular formula without the molecular mass of a compound?

Question 6

how to calculate relative atomic mass?

Answer 6

(abundance A x mass charge of A) + (abundance B x mass charge of B) ➗ total abundance

Question 7

how do you work out the formula of an ionic compound?

Answer 7

swap and drop method:
1. write ions
2. swap the charges
3. drop the charges
4. simplify to lowest whole number ratio (if needed)

Question 8

are salts an example of an ionic compound?

Answer 8

• yes, they can be hydrated or anhydrous (with or without water)