2 amount of substance
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what is Mr?
relative molecular mass
what is Ar?
relative atomic mass
define Mr
the mean mass of a molecule of a compound divided by 1/12 of the mass of a carbon12 isotope
define Ar
the mean mass of an atom of an element divided by 1/12 of the mean mass of an atom of carbon12 isotope
what is avogadros constant?
6.022x10^23
define avogadros constant
the number of atoms in 12g of C12
how do you calculate moles from mass and Mr/Ar?
moles = mass/Mr
where do you find the Ar of an element on the periodic table?
above the letters
what is the ideal gas equation?
pV=nRT
what do the letters stand for in the ideal gas equation? what are all the units for each?
p= pressure (Pa) V= volume (m^3) n= moles R= molar gas constant (always 8.31JKmol) T= temp (K)
how do you go from dm^3 to m^3?
divide by 1000
how do you go from cm^3 to m^3?
divide by 1000000
how do you go from °C to K?
+273
how do you go from kPa to Pa?
x1000
define empirical formula
simplest whole number ratio of atoms of each element
define molecular formula
actual number of atoms of each element
how do you find the empirical formula?
• divide mass of each element by Ar of that element (moles) • divide all moles by the smallest number of moles
how do you find the molecular formula of an element?
• divide mass of each element by Ar of that element (moles) • divide all answers by smallest value of moles • find the total mass of empirical formula • divide Mr given by mass of empirical formula
what is the equation for % atom economy?
mass of desired product/mass of reactants x100
what is the formula for % yield?
amount of specific product formed/ theoretical mass x100
what does a high atom economy mean?
• produce less waste • less expensive
why are %yields almost always under 100%?
• side reactions occur • reaction doesn’t go to completion • waste
how do you find moles from concentration and volume?
moles = conc x vol
what is 1dm in cm?
10