moles I 4.4 Flashcards
what is relative formula mass
the mass of a formula unit of a substance
how is the farm calculated
adding the relative atomic masses (RAMs) of atoms
what is percentage by mass
the mass of a substance that comes from a particular element
how to calculate the percentage by mass
%x = (mass of x / RFM) *100
what are moles
the unit of amount of substance
how is moles calculated
mass/RFM
what is empirical formula
the simplest mole ration of its elements
how to calculate empirical formula
-convert the masses(or %) into moles
-cancel down the mole ratio
-write the simplest mole ratio into a formula
what is molecular formula
the actual number of atoms in a molecule
how to calculate the molecular formula from empirical formula and RFM
-calculate how many times the empirical formula fits into the RFM by division
-multiply this value by the empirical formula
what is water of crystallisation
hydrated salt crystals contain water trapped inside them in a fixed mole ratio
how to calculate water of crystallisation
-calculate the mass of water lost
-draw a mass, moles, ration table
what do the balancing numbers in a balanced equation for a reaction tell us
how many moles of each reactant are needed and how many moles of each product are made
how to calculate the mass needed for a reaction
convert mass of reactant 2 into moles
use the mole ratio from the balancing numbers
covert moles of reactant 1 into mass
if there isn’t enough of a substance its
limiting
if there is more than enough of a substance its
in excess
how to find out which reactant is in excess
calculate how much of the other one would be needed to react with it, then compare with how much there actually
% yield=
experimental/theoretical x 100
what is experimental mass
measured in experiment
what is theoretical mass
calculated based on mass of reactant
