24. Stoichiometry II*

it's all about balance!

molecular formula

gives the number of atoms of each element present in a molecule of that compound

empirical formula

gives the simplest whole number ratio of the different types of atoms present

to calculate empirical formula given the % composition by mass

assume 100g sample, convert to moles, divide by smallest number and round, write out empirical formula

to calculate molecular formula when given empirical formula and rmm

empirical formula mass x n = rmm, empirical formula x n = molecular formula

to calculate empirical formula when given masses of reactants and products

write out word equation, find mass of each substance, convert to moles, use ratio to find empirical formula

theoretical yield

the yield that would be obtained if the experiment was 100% efficient

actual yield

the yield that is actually obtained in the experiment

percentage yield formula

actual yield/theoretical yield x 100

limiting reagent/reactant

the substance that limits the amount of products that can be made

reagent/reactant in excess

the substance of which there is more than needed