Ar + Mr and emperical + molecular formula

Define relative atomic mass (Ar)

The mean mass of an atom of an element, divided by one twelfth of the mean mass of an atom of the atom of the carbon-12 isotope

What is relative molecular mass?

The mean mass of a molecule of a compound divided by 1/12 of the mean mass of an atom of the carbon-12 isotope

* for ionic compounds, its known as relative formula mass

Define molecular formula

Actual number of each atom in the molecule

What must something have in order for it to be a molecule?

Have covalent bonding

→ CANNOT INVOLVE METALS i.e ionic / metallic bonding

What is the emperical formula?

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

* C6H12O6 → CH₂O

What does diatomic mean?

Consisting of 2 ions

Give some examples of diatomic substances

H₂ , N₂ , F₂ , O₂ , I₂ , Cl₂ , B₂

* Have No Fear Of Ice Cold Beer

Explain how to find the empirical formula of a substance with only known mass/percentage

1. Write the mass / percentage and divide it by its Ar

2. Divide the answers by the smallest answer

3. Find the simplest whole number ratio → if your answer cant be rounded up, scale all answers until reached a whole number

4. Write the empirical formula

Explain how to calculate the molecular formula from the empirical formula

1. Work out the empirical formula

2. Calculate the empirical mass (Ar of empirical formula)

3. Divide the given Mr by the empirical mass → gives you the multiple

4. Multiply the empirical formula by the ‘multiple’ → gives you the molecular formula