Amounts Of Substances Flashcards
Define relative molecular mass and relative formula mass
(Mass of a molecule of the compound) / 1/12 mass of one atom of 12C
(Mass of a one formula unit of an ionic compound) / 1/12 mass of one atom of 12C
Define the mole
The mole is the amount of substance that contains many particles as there are in exactly 12 g of carbon-12
Formula for number of atoms
Number of moles / avogadros constant
Define empirical and molecular formula
Empirical formula is the simplest whole number ratio of atoms of each element present in a compound.
Molecular formula is the actual number of atoms of each element present in a molecule.
Formula for percentage error
( Uncertainty / Value ) x 100
How to find water of crystallisation
Just find empirical formula
Formula for % yield
(Actual yield / Theoretical Yield) x100
Actual yield - the actual number of moles obtained from the product.
Theoretical yield - the number of moles that were expected to be obtained from the product.
Possible reasons for low % yield
-Incomplete reaction / reversible reaction
-Side reactions may occur
-Loss of product during transfer or purification steps
-Impurities in the reactants
If something decomposes it means
Its a reversible reaction
Formula for atom economy
(Mr of desired product / Sum of Mr of all the products) x 100
Addition, substitution and elimination reactions
Addition reactions have an atom economy if 100%
Substitution and elimination reactions have an atom economy below 100%
