Calculations

Question 1

Relative Formula Mass

Answer 1

Mr = the sum of all relative atomic masses for the elements.

Question 2

Empirical Formula

Answer 2

The simplest whole number ratio of the atoms in each element present.

Eg; C2H6 can be simplified to CH3

Question 3

Calculating Empirical Formula

Answer 3

For each element, divide the given masses by the Ar (Relative atomic mass).

Then by comparing the two results, divide them both by the smallest unit, this will give you the formula.

Question 4

Molecular Formula

Answer 4

Shows the actual amount of atoms of each element in the molecule, without it being simplified.

Question 5

Empirical to Molecular Formula

Answer 5

The relative atomic mass is usually given.

Calculate the Mr for each atom.

Then divide the relative atomic mass by the Mr.

Finally, multiple that answer with the empirical formula numbers to get the molecular formula.

Question 6

Moles

Answer 6

A unit for an amount of substance.

Avogadro’s Constant = 6.02 x 10(to the power of 23)

Question 7

Calculations for Moles

Answer 7

Moles = Mass / Mr

Question 8

Calculating Number of Particles

Answer 8

Particles = Avogadro Constant (6.02 x 10(23)) x mole

Question 9

Concentration

Answer 9

concentration in g dm-3 = mass of solute in g / volume in dm-3.

Question 10

Volume units

Answer 10

1dm(3) = 1000cm (3)

ml and cm are the same.