2.1.3 - Amount of substance

Question 1

Symbol unit for moles

Answer 1

Mol

Question 2

What is avogardo’s constant

Answer 2

• The number of particles per mole, 6.02 x 10²³_mol^-1

Question 3

What do they mean when they ask you to give and empirical formula ?

Answer 3

The simplest whole ratio of atoms of each element present in a compound.

Question 4

How do we calculate the empirical formula of a molecule/compound when a percentage is given instead for the elements.

Answer 4

1) If you find it easier set up a table like this.
2) Then divide the percentage of that element by its atomic mass to calculate the moles of that atom
3) Do this for each element
4) To find the empirical formula for that molecule/compound divide every element within that compound with the smallest number that you got when finding the answers to step 2/3.

make sure to practice this and look at the example below.

Question 5

How do we calculate the empirical formula of a compound when the mass are given instead.

Answer 5

1) If you find it easier set up a table like this.
2) Then divide the mass number of that element by its atomic mass to calculate the molar mass of that atom
3) Do this for each element
4) To find the empirical formula for that molecule/compound divide every element within that compound with the smallest number that you got when finding the answers to step 2/3.

make sure to practice this and look at the example below.