Question

Aspirin can be made in the laboratory by reacting acetic anhydride (C4H6O3) with salicylic acid (C7H6O3) to form aspirin (C9H8O4) and acetic acid (C2H4O2). The balanced equation is: C4H6O3+C7H6O3→C9H8O4+C2H4O2.In a laboratory synthesis, a student begins with 5.00 mL of acetic anhydride (density = 1.08 g / mL) and 2.08 g of salicylic acid. Once the reaction is complete, the student collects 2.07 g of aspirin. Determine the limiting reactant for the reaction?

Determine the theoretical yield of aspirin for the reaction?

Determine the percent yield of aspirin for the reaction.

Answer 1

Answer:

The limiting reactant for the reaction is 0.0151 moles salicylic acid

theoretical yield of aspirin for the reaction is

2.720 grams of aspirin

The percent yield of aspirin for the reaction = 76.103%

Explanation:

Aspirin can be made in the laboratory by reacting acetic anhydride (C4H6O3) with salicylic acid (C7H6O3) to form aspirin (C9H8O4) and acetic acid (C2H4O2). The balanced equation is: C4H6O3+C7H6O3→C9H8O4+C2H4O2.In a laboratory synthesis, a student begins with 5.00 mL of acetic anhydride (density = 1.08 g / mL) and 2.08 g of salicylic acid. Once the reaction is complete, the student collects 2.07 g of aspirin. Determine the limiting reactant for the reaction?

Determine the theoretical yield of aspirin for the reaction?

Determine the percent yield of aspirin for the reaction.

Given:

5.00 mL of acetic anhydride

Density of acetic anhydride = 1.08 g/mL

Mass of acetic anhydride = Vol × density

= 5.00mL × 1.08g/malt

= 5.4g of acetic anhydride

Moles of C4H6O3 = ?

Mole = mass/molar mass

5.4 grams of C4H6O3

Molar mass of C4H6O3 = 102.09 g/mol

Mole= 5.4g

-----------

102.09g/mol

= 0.0529 moles acetic anhydride

Given:

2.08g of C7H6O3

Molar mass of C7H6O3 = 138.12 g/mol

Mole= 2.08g

------------------

138.12g/mol

= 0.0151 moles salicylic acid

Therefore:

The limiting reactant for the reaction is 0.0151 moles salicylic acid

theoretical yield:

Equation of the reaction:

C4H6O3 + C7H6O3 --> C9H8O4 + C2H4O2

1 : 1 : 1 : 1

0.0151 moles salicylic acid produces an equal number of moles of aspirin = 0.0151 moles of aspirin

Therefore:

molar mass of aspirin: 180.16 g/mol

mass of aspirin = ?

Mass = mol x molar mass

0.0151 moles of aspirin × 180.16 g/mol C9H8O4

= 2.720 grams of aspirin

Therefore

theoretical yield of aspirin for the reaction is

2.720 grams of aspirin

percent yield for the reaction

Given

2.07g of aspirin in the question

2.720 grams of aspirin (theoretical yield)

Percent yield = given mass

----------------------------- × 100%

Theoretical mass

= 2.07g of aspirin

------------------------------------ × 100%

2.720 grams of aspirin 100

= 76.103%

The percent yield of aspirin for the reaction = 76.103%

Answer 2

Answer:

• The limiting reactant is salicylic acid

• Theoretical yield = 2.71 g aspirin

• Percent yield = 76.38%

Explanation:

C₄H₆O₃ + C₇H₆O₃ → C₉H₈O₄ + C₂H₄O₂

In order to determine the limiting reactant, we need to calculate the moles of each reactant, using their respective molecular weight.

• 2.08 g salicylic acid ÷ 138 g/mol = 0.01507 mol salicylic acid

In the case of acetic anhydride we also use its density:

• 5.00 mL acetic anhydride * 1.08 g/mL = 5.4 g acetic anhydride

• 5.4 g acetic anhydride ÷ 102 g/mol = 0.05294 mol acetic anhydride

1 mol of acetic anhydride will react with 1 mol of salicylic acid, and because there are more acetic anhydride moles than salicylic acid moles, then salicylic acid is the limiting reactant.

We calculate the theoretical yield and percent yield using the limiting reactant:

• 0.01507 mol salicylic acid * $\frac{1molAspirine}{1molSalicylic}$ = 0.01507 mol aspirin * 180 g/mol = 2.71 g aspirin

The percent yield is calculated using the experimental and the theoretical yield:

2.07 g / 2.71 g * 100% = 76.38%