Calculations Flashcards
(17 cards)
How to calculate relative formula mass (Mr)
Multiply relative atomic mass (Ar) of every element by the amount of atoms (small numbers)
How to work out a percentage
Small number/big number x 100
How to work out the percentage of an element in a compound
% of element = Ar of all atoms of element (element needed) /Mr of whole compound x100
What is a mole?
A mole is 6.02 x 10(23) things
How to work out moles
Moles = mass/Ar
How to work out mass from Ar and moles
Mass = moles x Mr
What is the avogadros constant?
The avigadros constant is 6.02 x 10(23)
Who is the avogadros constant named after?
Amadeo avogadro
How to work out number of atoms
Work out moles from moles v mass/!r
Number of atoms = number of moles x 6.02 x 10(23)
How do we work out molar ratio
Using the big numbers in front of reactants and products in an equation
(Equation may need to be balanced first)
What is meant by a limiting reagent?
The limiting reagent is the first reactant to get
used up (run out), and the reaction must stop.
It limits the amount of product made
What is meant by molar gas volume
• The volume of 1 mole of ANY gas is 24dm3
at room temperature and pressure (20oC and 1atm).
How to work out volume of gas (dm3)
volume of gas (dm3) = Number of moles x 24 dm3
How many cm3 is in 1dm3
1dm3 =1000cm3
How to calculate concentration
Concentration (g/dm3) = mass (g) / volume (dm3)
