How to guide to working out Empirical formula

Step by step guide to working out empirical formula by mass =]

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  • Created by: Maddison
  • Created on: 02-06-09 10:20
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Empirical and Molecular Formulae
The Empirical Formula of a compound is the simplest whole-number ratio of
atoms of each element present in a compound ­ the simplest mole ratio.
Empirical formulae are calculated from the masses of the elements in a
compound. The best way to work it out, I think, is to use a table...
Worked Example:
"Calculate the empirical formula of silicon oxide if 3.50g of silicon
combines with 4.00g of oxygen."
Si O
Mass (g)
Amount (mol)
Mole Ratio
Empirical
Formula
Here's the table you start off with. Fill in what you know...
Si O
Mass (g) 3.50
4.00
Amount (mol)
Mole Ratio
Empirical
Formula
Next, you calculate the amount of moles of each element you have. You do this
by dividing the mass in grams, by the molecular mass. (Remember that the mass
number is the top number on the Periodic table! ; ] )
Si O
Mass (g) 3.50
4.00
Amount (mol)

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Mole Ratio
Empirical
Formula
Now, you have to divide the amount of mol of each element by the
smallest number of moles you have ­ in this case, it's 0.125. ...And from this,
you're given a ratio, and therefore the Empirical formula!
Si O
Mass (g) 3.50
4.…read more

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