Amount of substance Flashcards
Define relative atomic mass
the average mass of an atom over 1/12th of the mass of one atom of 12C.
Define relative molecular mass
Average mass of a molecule over 1/12th of the mass of one atom of 12C.
Define relative formula mass
the sum of the relative atomic masses of the atoms ina formula unit of a compound.
working out relative atomic mass from isotopic abundance and isotopic mass.
isotopic abundance X isotopic mass
Add them up
Divide by 100
unit for concentration
mol dm^-3
formula for mol
mol= m/mr
avogadro constant
6.02 X 10^23
number of particles found in one mol
equation to find number of particles
mol X avogadro constant
concentration formula
mol/volume(dm^-3)
ideal gas equation
PV=nRT
p: pa
v: m^3
T: k
degrees celcius to kelvin
degrees celcius + 273
KPa to Pa
X 1000
Cm^3 to m^3
cube root
divide by 100
cube it
what is Empirical formula?
Empirical formula is the simplest whole number ratio of
atoms of each element in a compound.
what is molecular formula?
Molecular formula is the actual number of atoms of each
element in a compound.
how to work out empirical formula
percentage of each element/Ar
then divide all elements by the smallest number.
How to work out molecular formula
work out empirical mass
divide molecular mass by empirical mass
multiply empirical formula by the answer from step above
Atom economy formula
mr of desired product / sum of mr of all reactants X 100
Law of conservation of mass
in a closed system, mass of the system remains constant over time and cannot change.
(substances can’t be added or removed)
what is a spectator ion?
an ion that doesn’t change state or charge in reaction
state symbols
metals (s)
Acids (aq)
certain elements e.g. oxygen, nitrogen,hydrogen (g)
Reactions in solutions (aq)
percentage yield
(actual yield / theoretical yield) X 100
