Chemical Formulae, Equations and Calculations

Question 1

Solid, Liquid. Gas, Aqueous

Answer 1

(s), (l), (g), (aq)

Question 2

Calculating Mr

Answer 2

Sum of all atoms present: E.g. H2O
2 x 1 + 16 = 18

Question 3

Mole:

Answer 3

The unit for amount of a substance

Question 4

Formula for Moles:

Answer 4

Moles = Mass/Mr

Question 5

%yield

Answer 5

actual amount of product/theoretical amount of product

Question 6

Empirical Formula:

Answer 6

The simplest whole number ratio between atoms/ions in a compound
E.g. Pentene C5H10 -> CH2

Question 7

Molecular Formula:

Answer 7

The actual number of atoms of each type of element in a molecule

Question 8

Calculating Empirical Formula

Answer 8

1. Put symbols for each element at top of page
2. Underneath, write masses of each element combining.
3. Divide by their relative atomic mass
4. Divide all the numbers by the smallest of these numbers to give a whole number ratio
5. Use this to give the empirical formula
   (If ratio is 1:1.5 multiply by 2, 1:1.33 x 3, 1:1.25 x 4)

Question 9

Calculating Molecular Formula

Answer 9

1. Calculate mass of empirical formula
2. Find out the number of times the relative mass of the empirical formula goes into the Mr of the compound
3. Multiply the empirical formula by this number