Reacting Masses and Empirical

Formulas

· You can use moles to calculate masses in reactions. First you write out a balanced

equation, then calculate the number of moles in the mass you have been given. Then

look at the ratio of moles in the equation. Finally calculate the mass of moles in what

you are trying to find out.

· Percentage composition by mass = Ar x no. of atoms of element / Mr of whole

compound x100

· Empirical formulas give the smallest whole number ratio of atoms in a compound.

You can work it out by following simple steps.

· 1. List the elements

· 2. Write in the experimental masses or percentages

· 3. Divide by the Ar for each element

· 4. Turn the numbers you get into a simple ratio by multiplying and/or dividing them

· 5. Get its ratio in the simplest form, and that's the empirical formula.

e.g. the chemical formula for ethane is CH and the empirical formula is CH…read more

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