1.2 The mole concept Flashcards
to know the quantity the substance requires to react, what do we need to know?
the atoms, molecules, or ions in a specific amount
the mass of an ion, molecule, and particles that make it up are…
very small, so we use a convenient method
definition of relative atomic mass (Ar) of an element
it is the average of the masses of the isotopes in a naturally occurring sample of the element relative to the mass of 1/12 of an atom of carbon-12
definition of relative molecular mass (Mr) of a compound
it is the mass of molecules of that compound relative to the mass of 1/12 of an atom of carbon-12
definition of relative formula mass
it is the mass of one formula unit relative to the mass of 1/12 of an atom of carbon-12
when do we use the relative formula mass?
when a compound is made up of ions so it doesn’t contain discrete molecules
what is the relative formula mass used to refer to?
to the mass of the formula unit of an ionic compound
definition of one mole
it is the amount of a substance that contains the same number of particles as there are carbon atoms in a 12g of carbon-12
what is the number of Avogadro’s constant?
6.02x10^23
how do you find the number of moles (n)?
mass of a substance/ molar mass
definition of molar mass (M) of a substance
it is its Ar or Mr in grams. The unit is gmol^-1
how do you find the mass of one molecule?
molar mass/ Avogadro’s constant
how do you find the % by mass of an element?
number of atoms of the element * Ar / Mr
