Chemistry equations (unit 2)

Hope this helps you to remember some of the equations we need to learn, there are SO many !!

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  • Created by: Jemima
  • Created on: 22-05-12 12:41

Number of moles

Number of moles   =           Mass in g (of element or compound)

                                         ------------------------------------------------

                                               Mr (of element or compound)

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Percentage mass of an element in a compound

Percentage Mass of an Element in a Compound =


        Ar x No of atoms (of that element)

        -----------------------------------------           x100

               Mr (of whole compound

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Finding the empirical formula

  • List all the elements in the compound
  • Underneath them write experimental masses or percentages
  • Divide each mass or percentage by the Ar for that element 
  • Turn numbers you get into simple ratio by dividing by the smallest number or multiplying
  • Get the ratio in the simplest form 

BOOOM ITS AS EASY AS THAT!

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Calculating masses in reactions

  • Write out the balanced equation
  • Work out the Mr (just for the two bits you want)
  • Apply the rule; DIVIDE TO GET ONE THEN MULTIPLY TO GET ALL

SIMPLES

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Percentage Yield

         Actual yield (grams)

    --------------------------------        x100

       Predicted yield (grams)

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Rate of reaction

Amount of reactant used or amount of product formed

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                                     Time

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