% purity& what it means
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actual moles of acid/theoretical moles of aspirin in sample
%> 100: most likely due to the presence of un-reacted salicylic acid
as well as acetic acid by-product
%<50: the product may still be wet so that the actual moles of aspirin
are much smaller than what they are supposed to be
,random errors
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unknown/unpredictable changes or environmental conditions. It
becomes a systematic error once the source of random error is
known. Strongly affects the precision of a result.
w/w%
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g/g *100%
grams of solute/100grams solution
maximum amount of a product
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use the limiting reagent and multiply moles by molar weight
major difficult of crystallization
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, putting too much solvent in and not getting the right product because
the more times you crystalize the less product you have
light transmission formula
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I(light being transmitted)/I₀(light coming in)=10^(εlc)
This turns into beer's law (A=-logT=εLC)
identity
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melting point confirms but does not prove the identity of any given
compound since many have similar melting points
Possible kinds of impurities encountered during recrystallization
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1. Mechanical impurities (dust, particles, particles of paper, etc). Can
be easily removed by filtering the solvent while it is hot.
2. Colored impurities. Can be removed by warming the solvent with a
small amount of decolorizing carbon.
3. Soluble impurities. Can be removed by choosing a solvent so that
the impurities will be dissolved even if the solvent is cold
(Possible product impurities: acetic anhydride (reactant), acetic acid
Give this one a try later!
actual moles of acid/theoretical moles of aspirin in sample
%> 100: most likely due to the presence of un-reacted salicylic acid
as well as acetic acid by-product
%<50: the product may still be wet so that the actual moles of aspirin
are much smaller than what they are supposed to be
,random errors
Give this one a try later!
unknown/unpredictable changes or environmental conditions. It
becomes a systematic error once the source of random error is
known. Strongly affects the precision of a result.
w/w%
Give this one a try later!
g/g *100%
grams of solute/100grams solution
maximum amount of a product
Give this one a try later!
use the limiting reagent and multiply moles by molar weight
major difficult of crystallization
Give this one a try later!
, putting too much solvent in and not getting the right product because
the more times you crystalize the less product you have
light transmission formula
Give this one a try later!
I(light being transmitted)/I₀(light coming in)=10^(εlc)
This turns into beer's law (A=-logT=εLC)
identity
Give this one a try later!
melting point confirms but does not prove the identity of any given
compound since many have similar melting points
Possible kinds of impurities encountered during recrystallization
Give this one a try later!
1. Mechanical impurities (dust, particles, particles of paper, etc). Can
be easily removed by filtering the solvent while it is hot.
2. Colored impurities. Can be removed by warming the solvent with a
small amount of decolorizing carbon.
3. Soluble impurities. Can be removed by choosing a solvent so that
the impurities will be dissolved even if the solvent is cold
(Possible product impurities: acetic anhydride (reactant), acetic acid
