Quantifying atoms and compounds Flashcards
Mass spectrometer
used to confirm the existence of isotopes
Percentage abundance using the spectrum
% abundance= peak height / total peak height x 100
Mass spectrum
Graph of the relative mass of isotopes, calibrated on the C12 scale, plotted against the percentage abundance
RAM calculation
E(RIM x %) / 100
Mole
unit for counting particles
n
amount in moles
Avogadro’s number
6.02 x 10^23
NA
Avogadro’s number
Relative Mr
Molar mass
Sum of the relative atomic masses of elements in the molecular formula
Mr
g mol ^-1
Mass of one mole of a particular element or compound
n=
m/Mr- amount
Stoichometry
n(unknown)= coefficient(unknown) / coefficient(known) x n(known)
Percentage composition of an element
Mr of that element x number of atoms of that element in compound/ Mr of compound x 100
Empirical formula
Shows the elements and simplest whole number ratio of atoms
Molecular formula
shows exact number of atoms of each element in a molecule
X (molecular formula)=
Mr(MF) / Mr(EF)
Elemental analysis of an organic compound procedure
- Mass of organic compound recorded
- Complete combustion occurs through apparatus
- Sodium hydroxide solution absorbs carbon dioxide in organic compound. Mass of carbon dioxide equal to mass increase of sodium hydroxide (carbon dioxide absorber)
- Drying agents absorb water in organic compound. Mass of water is equal to mass increase of drying agents (water absorber)
Elemental analysis to determine empirical formula
- Calculate mass of carbon from mass of carbon dioxide produced via stoichometry
- Calculate mass of hydrogen from mass of water produced
- Subtract mass of carbon plus hydrogen from original mass to find mass of oxygen
- Using masses of O, C and H, calculate empirical formula
RAM
Weighted average of isotopic masses of atoms of an element compared to the standard C12 isotope
n= (not mass)
N / NA
N
number of particles-how many
RIM
mass of an atom of an isotope compared to the mass of a carbon 12 atom
Relative molecular mass
Mass of 1 molecule of a substance compared to the the mass of 1 atom of C12 taken as 12 exactly
Molar mass
Mass, in grams, of 1 mole of a substance
