Ok so I have a Chemistry make up exam tomorrowso..?
Answer:
moles = mass / molecular weight
molecular weight can be found from adding up the atomic masses given in a periodic table
molarity of A = moles A / liters solution
example 10 moles salt in 1 liter water = 10 moles / 1 liter = 10 molar salt solution.
molality of A = moles A / kg solvent
example:
117 grams NaCl dissolved in 4 kg water
mw NaCl = 58.5 g/mole (from periodic table)
so moles NaCl = 117 g / (58.5 g/mole) = 2 moles
molality = 2 moles / 4 kg water = 0.5 molal
molar fraction = moles A / moles total
mass fraction = mass A / mass total
normality = equivalents / liters.
this is a bit abstract. in acids and bases, the H+ or OH- part are considered "equivalents" of acid. so if you had HCl (hydrochloric acid) there would be 1 molecule of H+ per molecule of HCl. or 1 mole of H+ per mole of HCl. for H2SO4 (sulfuric acid), there are two moles H+ per mole of acid (from H2...).
examples.
109.5 grams HCl in 6 liters water.
mw HCl = 36.5, moles HCl = 109.5 / 36.5 = 3 moles HCl
1 H per 1 HCl ----> 3 moles HCl
normality = 3 moles HCl / 6 liter water = 0.5 normal.
49 grams H2SO4 in 4 liters water.
mw H2SO4 = 98 g/mole, moles H2SO4 = 49/98 = 0.5 moles
2 moles H+ per 1 mole H2SO4 ---> 2 x 0.5 = 1 mole H+
normality = 1 mole H+ / 4 liters water = 0.25 normal
You will find everything you need right here!
http://en.wikipedia.org/wiki/concentrati...
good Luck!
Molarity is number of moles per litre of solution
Molalilty is number of moles per kg of solvent
Molar Fraction is number of moles of a /number of moles of a and b
Mass percent is mass of a/mass of a + mass of b
Normality is number of equivalents per litre of solution
I would say if you have an exam tomorrow and don't know a better source than FunQA.com for finding basic formulas needed for said exam...
don't bother going to it.
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