Amount Of Substance Flashcards
Define relative atomic mass
The Weighted average mass of an atom of an element taking into account its naturally occurring isotopes relative to 1/12 th the mass of an atom of carbon 12
Define relative molecular mass
The mass of a molecule compared to the 1/12 the relative atomic mass of an atom of carbon 12
What is relative formula mass?
Similar to Mr however this is used for ionic compounds as they do not exist as molecules.
What is a mole?
The amount of substance that contains the same number of atoms as 12g of carbon 12
Avagadros constant:
6.02x10^23
What’s is empirical formula?
The simplest whole number ratio of atoms in each element present in a compound
What is stoichiometry?
The quantitative relationship between reactants and products in a balanced equation.
What equations do we use to find moles?
Moles = mass / Mr
Moles = volume x concentration / 1000
What is the ideal gas equation?
PV=nRT
P-pressure V-volume n-number of moles R-gas constant (8.314) T-temperature
What key assumptions are made when using the gas constant?
Any intermolecular forced between the gas molecules is negligible
Relative to the volume of their container the volume occupied by the molecules themselves is negligible.
How do you find the empirical formula?
- Find the masses of each of the elements present in a compound
- Work out the number of moles of atoms of each element
- Convert the number of moles of each element into a whole number ratio.
What is the molecular formula?
The actual number of atoms of each element in a molecule or compound.
What is the equation for atom economy?
Atom economy= mass if desired product / total mass of reactants
What is the equation for percentage yield?
% yield= actual yield / theoretical yield
What may cause the percentage yield to not be 100%?
Some reactant may remain unreacted
Some reactant may be lost
The reaction may not have gone to completion.
How do you calculate percentage uncertainty
% uncertainty = absolute uncertainty / measured value x100
