Chemistry equations (unit 2)

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

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

                                               Mr (of element or compound)

Percentage Mass of an Element in a Compound =

        Ar x No of atoms (of that element)

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

               Mr (of whole compound

• 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!

• 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

         Actual yield (grams)

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

       Predicted yield (grams)

Amount of reactant used or amount of product formed

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                                     Time