the masses of atoms are compared by measuring them relative to atoms of carbon-12.
the relative formula mass of a compound can be worked out by adding up the relative atomic masses of the elements in it, in the ration shown by the formula.
one mole of any substance is the relative formula mass in grams
number of moles = mass in grams/ relative formula mass
avogadro's constant is 6.02 x 10^23
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C4.2: Equations and Calculations
balanced symbol equations tell you the number of moles of substances involved in a chemical reaction
you can use balanced symbol equations to calculate the masses of reactants and products in a chemical reaction
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C4.3: From Masses to Balanced Equations
balanced symbol equations can be deduced by the masses (and the ratio of the numbers of moles) of substances involved in a chemical reaction
the reactant that gets used up first is the limiting factor
this is the reactant that is NOT in excess
amounts of product formed in a chemical reaction are determined by the limiting reactant.
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C4.4: Expressing Concentrations
concentration is measures in g/dm^3
concentration = amount of solute (g) / volume of solution (dm^3)
dm^3 = 1000cm^3
to calculate the mass of a solute in a certain volume with a known concentration:
calculate the mass in grams for 1dm^3 of solution
calulate the mass in grams of solute im 1cm^3 (divide by 1000)
calculate the mass in grams of solute in the given volume of solution
a more concentrated solution has more solute in the same volume of solution than a less concentrated solution
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