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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
Write the mass / percentage and divide it by its Ar
Divide the answers by the smallest answer
Find the simplest whole number ratio → if your answer cant be rounded up, scale all answers until reached a whole number
Write the empirical formula
Explain how to calculate the molecular formula from the empirical formula
Work out the empirical formula
Calculate the empirical mass (Ar of empirical formula)
Divide the given Mr by the empirical mass → gives you the multiple
Multiply the empirical formula by the ‘multiple’ → gives you the molecular formula