using moles
what is a mole
the number of particles obtained by weighing out Ar or Mr
how is a mole written
6.02 times 10^23 the symbol of mole is mol
how to find molar mass
write down symbols and formula of a substance -find its Mr or Ar -express its mass in grams
calculation with moles
number of moles in mass = mass /mass of moles
how to calculate mass from an equation
-write a balanced equation -write Ar or Mr -using Ar or Mr change mole into grams -this gives theoretical masses
avogrados law
one mol of gas has the same volume as all other gases at room temperature and a pressure of 24dm
how to find the concentration of a solution in moles
find Mr of the solute -use equation ammount of solute/volume of solution
how to find the amount of solute in a solution
-use equation amount of solute=concentration times volume -convert moles to grams by multiplying Mr
what does the emperical formula tell you
-how many moles of different atoms combine -how many grams of different elements combine
how to find the empirical formula
find mass -change grams to moles -find ratio -write formula
what is the empirical formula
the empirical formula shows the simplest ratio in which atoms combine to form a compound
an experiment to find the empirical formula
1 weigh out a crucible lid eempty and add a coil of magnesium ribbon and weigh again to find the mass of magnesium 2 heat the crucible allowing oxygen to enter by raising the lid 3 let crucible cool and weigh again the mass has increased due to oxygen
the formula of an ionic compound
is the same as its empirical formula
the formula of a molecular compound
shows the actual number of atoms that combine to form a molecule -it gives more information than the empirical formula
what do you need to know to find molecular formula
-empirical mass -empirical formula -the relative molecular mass
how to find the molecular formula
Mr/empirical mass -multiply number of atoms in the empiricla formula by n
yield
amount of product obtained from reaction
theoretical mass of yield
mass of product in a reaction is the mass obtained by calculation
calculation to find purity
actual mass of product obtained/ theoretical mass
boiling points in realtion to purity
-impurites lower melting points and raise boiling points -the more impure the greater the change