# Moles - Calculations

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How to work out moles?
Mass / Formula Mass
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What volume of gas does 1 mole occupy?
24dm3 (1dm3 = 1000cm3)
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How to work out moles in gases?
Volume / 24dm3
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How to work out empirical formula? (Step 1) e.g butane
Find formula mass of butane = 48 + 10 = 56
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How to work out empirical formula? (Step 2) e.g butane
Then you find the percentage of each element involved - to do this you put their formula mass over total formula mass and x 100 e.g %C 48/58 x 100 = 82.8%
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How to work out empirical formula? (Step 3) e.g butane
Percentage / formula mass of said element ( for 1 of it) - this then gives you the moles e.g. 82..8 / 12 = 6.9 moles of hydrogen
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How to work out empirical formula? (Step 4) e.g butane
Now write the mole ratio and divide each side by the small number - when both numbers are whole for the first time in the ratio that is your empirical formula
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How to find percentage yield?
Actual yield / predicted yield (x 100)
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What mass of sodium hydroxide can be made by reacting (y) grams of sodium water? (Step 1)
Write out equation
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What mass of sodium hydroxide can be made by reacting (y) grams of sodium water? (Step 2)
Write mole ratio
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What mass of sodium hydroxide can be made by reacting (y) grams of sodium water? (Step 3)
(y) grams / formula mass = moles
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What mass of sodium hydroxide can be made by reacting (y) grams of sodium water? (Step 3)
Now that you have moles you can apply it and sub it into the mole ratio
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What mass of sodium hydroxide can be made by reacting (y) grams of sodium water? (Step 4)
moles (of said substance) x formula mass = mass
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Find mass of 6200cm3 of SO2 at RTP? (Step 1)
First you find the moles - volume / 24dm3 (or 24 000 cm3) = 6200 / 24 000 = 0.26 moles
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Find mass of 6200cm3 of SO2 at RTP? (Step 2)
Find mass = moles x formula mass = 0.26 x 64 = 16.64g of SO2 at RTP
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How to find concentration ?
Mass (g) / Volume (dm3) = Concentration (g/dm3) or Moles (mol) / Volume (dm3) = Concentration (mol/dm3) (M)
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How to go from cm3 to dm3?
divide by 1000
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How to go from dm3 to cm3?
times by 1000
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## Other cards in this set

### Card 2

#### Front

24dm3 (1dm3 = 1000cm3)

#### Back

What volume of gas does 1 mole occupy?

Volume / 24dm3

### Card 4

#### Front

Find formula mass of butane = 48 + 10 = 56

### Card 5

#### Front

Then you find the percentage of each element involved - to do this you put their formula mass over total formula mass and x 100 e.g %C 48/58 x 100 = 82.8%