Chem Lab final
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How do you know if a molecule will be soluble in water or not?
molecules dissolve in water becasue they have the ability to hydrogem bond (they have F,O,N,Cl in their structure). The more sites of hydrogen bonds the more soluble the molecule is.
golden rule of solubility
- like dissolves like (take the whole molecule)
- methanol is soluble in water
- octanol is not
what reagents were used to make aspirin (acetylsalicylic acid)?
salicylic acid + acetic anhydride = aspirin + acetic acid
what modification takes place on salicylic acid to make aspirin?
phenol group on salycilic acid transformed into an ester group in aspirin
what functional groups does aspirin have?
- carboxylic acid
- benzene ring
what catalized the reaction of salicylic acid and acetic anhydride?
the strong acid (phosphoric acid)
is the aspirin reaction reversible?
- yes old aspirin often has a vinegar smell due to the precence of acetic acid
- test by adding iron (III) chloride to aspirn it will turn violet if salicylic acid is present.
how do you calculate the theoretical yield of aspirin from salicylic acid?
- 1:1 ratio of moles of salicylic acid used and aspirin produced
- every 1 mole of salicylic acid used will equal 1 mole of aspirin.
- 1) determine what 1 mole of salicylic acid is (C7H6O3) 1mole = 138g found from periodic table
- 2) use how many grams of salicylic acid you started with 3.0grams and convert that to moles 3.0g(1mol/138g)=0.02 mol salicylic acid
- 3) determine grams per mole of aspirin (C9H8O4) = 180g/mol
- 4) convert salicylic acid mole to grams of aspirin 0,02mol salicylic acid(180g/1mol)=3.6g aspirin
how do you calculate the percent yield of aspirn from salicylic acid?
(mass of dried product made g /theoretical yield g )x100= percent yield
what is the difference between and acid and a base?
- Acid is proton donor and produce hydronium ions (H3O+)
- Bases are proton acceptor and produce hydroxide ions (OH-)
Ph is a measure of what?
The amount of hydronium ions in a solution (H3O+)
what is relationship between hydronium ions in solutions and hydroxide ions?
- as long as you have either the pH or the amount of OH or H3O then you can figure out all of the other numbers
- (remember 1X10-14 is a ver small number compared to 10-1)
what is a buffer and how does it work?
buffer = a solution that keep the pH constant consists of a weak acid and conjugate base or weak base and conjugate acid
- the acid shock absorbs the hydroxide ions when added to system and the base shock absorbs the hydronium ions when added to the system
- (acid absorbs base)(base absorbs acid)
what is the affect of CO2 on the pH of a solution?
It decreases it making it more acidic
what are some antacids and how much HCl will the neutralize?
- 1calcium carbonate neutralizes 2HCl
- 1magnesium hydroxide neutralizes 2HCl
- 1 sodium bicarbonate neutralizes 1HCl
- 1aluminum hydroxide neutralizes 3HCl
explain antacid procedure
- 1.) start with acid + antacid
- 2.) add acid until all of the antacid is consumed (color change to yellow)
- 3.) add base until color change to blue
- 4.) Base and aicd on 1:1 ration (amount base added = amount acid used to consume antacid tablet)
- 5.) ml used to consume antacid = acid added (total) - base added
to find moles of HCl you have to know the molarity of solution and liters but what is equation?
moles= molarity x Liters
how do you find theoretical amnt HCl a tablet should be able to consume?
- know the ratio of consumption 1:2, 1:1, 1:3 etc.
- determine moles of active ingredient in tablet (grams to moles conversion)
- convert moles of tablet to moles of HCl based upon ratio
isoelectric point =
the point at which a molecules surface carries no net electrical charge
when does a protein become insoluble?
at its isoelectic point the protein will precipitate out of solution
when is a protein soluble in solution
at a pH above or below its isoelectic point
what is proteins charge when below its isoelectric point? why?
overall charge is positive becasue there are excess H+ in solution
protein charge when above isoelectric point? why
overall charge is negative becsasue there are excess OH-in solution
What is Casein?
The most abudant protein in milk
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