Chemical calculations Flashcards
Relative atomic mass
Average mass of one atom of the element relevant to 1/12 of the mass of one atom of carbon 12
relative isotopic mass
Average mass of one atom to isotope relevant to 1/12 of the mass of one atom of carbon 12
Amount of substances
mol= mass x Mr
Mol= PV/RT
Mol= CxV/1000
Atom economy
Mr of required Product/ Mr of total reactants
x100
empirical formula
smallest whole number ratio of atoms of each element in a compound
ideal gas equation
PV=nRT
P-Pressure in pascals x1000 from Kpa
V-volume in m3 /1000 from dm
n-moles
R- gas constant 8.31 JK-1mol-1
T- temp in K +273 from celcius
Molar mass
Mass of one mole of a substance in gmol-1
percentage yield
actual/theoretical x100
Molecular forumula
Mr of molecule / empirical Mr
Mass spectrometer
Technique used to identify compounds and determine their relative molecular mass
ionisation 1
A sample of Electrons are vaporised and injected into the mass spectometer where high voltage is passed over the chamber causing electrons to be removed from the atoms leaving plus charged ions in the chamber
acceleration 2
The positively charged ions are then accelerated towards negatively charged detection plate
deflection 3
Ions are then deflected by a magnetic field into a curved path radius
Path is dependent on the charge and mass of ion
detection 4
When the positive ions hit the negatively charged detection plate they gain an electron producing a flow of charge
The greater the abundance the greater the current produced
why is there a vaccum
A vacuum is needed inside the apparatus so that ions produced in the chamber have a free run through the machine without hitting air molecules
