2) Atoms, molecules and stoichiometry Flashcards
Relative atomic mass (Ar)
the weighed average mass of an atom of an element compared with 1/12 of the mass of an atom of carbon-12
Relative isotope mass
the mass of an atom of an isotope as compared to 1/12 of the mass of an atom of carbon-12
Relative molecular mass (Mr)
the weighted average mass of 1 molecule of an element or compound compared with 1/12 of the mass of an atom of carbon-12
Relative formula mass
the weighted average mass of 1 unit of a substance compared with 1/12 of the mass of an atom of carbon-12
Ionic equations
example in notes
The mole- Avogadro’s constant
number of particles/atoms/molecules= 6.02 x 10 ^ 23 x moles
The mole- Mass and Mr
triangle in notes
Conversion of units
cm^3 to dm^3= /1000
dm^3 to cm^3 = x 1000
The mole- Solutions
triangle in notes
Concentration in g/dm^3 = mass of substance (g) /volume (dm^3)
The mole- Gasses
triangle in notes
Empirical formula
- the simplest whole ratio of elements in a compound
Steps: (table)
1) Write out the elements involved
2) Write the % as masses
3) Divide the masses by relative atomic mass to get the moles
4) Divide all the numbers by the smallest number of moles
Calculating water of crystallisation
1) Write out the 2 molecules involved
2) Write the masses of each molecule
3) Divide these by relative molecular mass to get number of moles
4) Divide all the numbers by the smallest number of moles
How to work out molecular formula
1) Work out Mr of empirical formula
2) Divide by Mr of molecular formula
3) Use that number to multiply all atoms in empirical formula
Using equations to work out masses
(Calculating a theoretical mass from an equation)
1) Write out the equation and balance it
2) Work out Mr/Ar of species involved. Write these as mass in g
3) Divide the one side by the answer previous to this and do the same to the other side
4) Multiply that answer by the amount they want
*example in notes
