7 CHEMICAL CALCULATIONS (mol) Flashcards
how to calculate relative atomic mass (Ar)
js take it from the periodic table
[(% x mass) of each isotope added up]
how to calculate relative molecular mass (Mr)
all the Ar added up
O = 16.0 –> Ar
O3 = 16.0x3=48 –>Mr
how to calculate percentage composition of a compound
Ar of the element / Mr of the compound
% of H in H2O
H=1x2
O=16.0
2/16+2 = 1/9
calculate percentage composition of water in a compound
its the same as b4 js tat now H2O is considered 1 element
5(H2O) = 5 x 18
5(O) = 5 x 16
how much is one mole
6.02 x 10^23
relationship between
mass(g), number of moles(mol), molar mass(Ar,Mr)
its the same as the dst triangle
mass(g) on top
moles (mol) molar mass (Ar.Mr)
what is the empirical formula for
the empirical formula of a compound is the simplest formula which shows the ratio of the atoms of the different elements in the compounds.
formula for empirical formula
- mass(g) of each element (given in qn)
- molar mass(Ar,Mr) of element (given in period table)
- no. of moles(mol) DST it g/Mr
4.Mole ratio (divide each value by the smallest value) from 3. - simple ratigo it