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
