1) Determine % yield of aspirin 2) compared the melting point of the crude and t
ID: 581077 • Letter: 1
Question
1) Determine % yield of aspirin 2) compared the melting point of the crude and the recrystallized aspirin with the theoretical melting point . a) Determine the % error. AaBbCcl Aab I Normal No Results Salicylic acid 1.0g Weighing paper 0.2152g 2.5ml Acetic H3PO4 Crude Weight Crude Melting Point 2-3 drops 1.0021g 130 C Part 2 Recrystallization 250m 0.3804g 0.2227 0.75ml 02416g 135 C Group aspirin weighted Filter Paper Ethanol Weight of recrystallized aspirin Melting Point of recrystallized aspirin
Explanation / Answer
Q1
% yield = actual/theoretical * 100%
theoretical >
1 g of S.A acid = mass/MW = 1/138.122 = 0.0072399 mol
mol of Acetic anhydriide A,A
mass of AA = D*V = 2.5*1.08 = 2.7 g
MW of AA = 102.09
mol = (mass/MW= (2.7/102.09 ) = 0.02644
ratio is 1:1 so
S.Acid is limiting
1 mol of S.Acid = 1 mol of aspirin
0.0072399 mol --> 0.0072399 mol
mass of aspirin expected = mol*MW = 0.0072399 *180 = 1.303182 g expected
then
%Yield = 1.0021/1.303182*100 = 76.89
2) compared the melting point of the crude and the recrystallized aspirin with the theoretical melting point .
crude point --> 130°C
recrystallized point --> 135°C
theoretical melting point = Actual point = 135°C
therefore, the recrystallization has purified the aspirin
a)
Error --> (obtained-real)/real*!00% = (130-135)/135*100 = 3.7%
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