Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: sam12103 on October 13, 2009, 02:12:51 AM
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1. If an aqueous solution ____ is added to a mixture of Ba^2+ and Fe^3+, the barium ion will precipitate, but the iron ion will remain in solution
a.NaOH
b.Na2SO4
c.K3PO4
d.KCl
e.Pb(NO3)2
answer is Na2SO4
but how and why did they get that answer, I don't understand. Can you please explain to me how they got the answer.
2. Aspirin (C9H8O4) is produced by the reaction of salicylic acid (M=138.1 g/mol) and acetic anhydride (M=102.1 g/mol)
C7H6O3 (s) + C4H6O3 (l) -> C9H8O4 (s) + C2H4O2 (l)
If you mix 2.00 g grams if each reactant, what mass of aspirin (M=180.2 g/mol) can theoretically be obtained?
a. 2.00 g
b. 2.61 g
c. 2.71 g
d. 3.53 g
e. 4.00 g
the answer is 2.61 g, can you please explain how to get this answer, what steps to take etc. I am very confused on how to solve this problem too.
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1. Google solubility rules.
2. Basic stoichiometry & limiting reagent:
http://www.chembuddy.com/?left=balancing-stoichiometry&right=stoichiometric-calculations
http://www.chembuddy.com/?left=balancing-stoichiometry&right=limiting-reagents
(basic assuming you know how to convert between masses and moles).
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Im pretty sure the first one has something to do with solubility rules.
For the second question, first work out the moles of the limiting reagent (i think thats the term i should be using). Then use the formula n=mass / molar mass. Using the value u get for n, sub it into the same formula again except this time using the molar mass of aspirin. This should give you a value of 2.61