Question

Given the following equation, what would be the theoretical yield in grams of acetylsalicylic acid (C9H8O4) that can be produced from the reaction between 2.0 g of salicylic acid (C7H6O3) and 8.0 g of acetic anhydride (C4H6O3)

Answer 1

Answer:

The correct answer is 2.6 g C₉H₈O₄

Explanation:

-First we have to write and to balance the chemical equation:

C₇H₆O₃ + C₄H₆O₃ ⇄ C₉H₈O₄ + C₂H₄O₂

-Then, we calculate the molecular masses of reactants and products:

1 mol C₇H₆O₃= (12 g/mol C x 7) + (1 g/mol H x 6) + (16 g/mol O x 3)= 138 g

1 mol C₄H₆O₃= (12 g/mol C x 4) + (1 g/mol H x 6) + (16 g/mol O x 3)= 102 g

1 mol C₉H₈O₄= (12 g/mol C x 9) + (1 g/mol H x 8) + (16 g/mol O x 4)= 180 g

1 mol C₂H₄O₂= (12 g/mol C x 2) + (1 g/mol H x 4) + (16 g/mol O x 2)= 60 g

The mass balance is correct because:

mass reactants = mass products

138 g + 102 g = 180 g + 60 g

     240 g       =     240 g

-Now we use the masses from the chemical equation to calculate how reactant we need. We know that 138 g of salicylic acid (C₇H₆O₃) react with 102 g of acetic anhydride (C₄H₆O₃). So, the grams of acetic anhydride we need to react with 2 g of salicylic acid will be:

138 g C₇H₆O₃------------------- 102 g C₄H₆O₃

2.0 g C₇H₆O₃ -------------------- x= (2.0 x 102)/138 = 1.48 g C₄H₆O₃

If we compare, the amount of C₄H₆O₃ we need (1.48 g) is lesser than the amount we have (8 g), so C₄H₆O₃ is the excess reactant and C₇H₆O₃ is the limiting reactant.

- Finally, we use the limiting reactant to calculate the theoretical yield in grams of C₉H₈O₄. From the chemical equation, we know that 138 g C₇H₆O₃ yield 180 g of C₉H₈O₄. We have 2.0 g, so:

138 g C₇H₆O₃------------------- 180 g C₉H₈O₄

2.0 g C₇H₆O₃ -------------------- x= (2.0 x 180)/138 = 2.6 g C₉H₈O₄

Answer 2

Answer:

mass of C9H8O4  = 2.61 g

Explanation:

Firstly, we write the chemical equation of the reaction and we balance it.

C7H6O3  = salicylic acid

C4H6O3 =  acetic anhydride

C9H8O4) = acetylsalicylic acid

C7H6O3 + C4H6O3 → C9H8O4 + C2H4O2

We need to get the limiting reactant

molar mass of C7H6O3  = 138.1 g

moles  =  2 / 138.1  = 0.01448225923 moles

molar mass of C4H6O3  = 102.1 g

moles = 8 / 102.1  = 0.07835455435  moles

molar mass of C9H8O4 = 180.2 g

The limiting reactant is C7H6O3 and it will be used to determine the yield of C9H8O4 .

if 138.1 g of  C7H6O3  produces  180.2 g of C9H8O4

2 g of  C7H6O3 will produce ? grams of C9H8O4

cross multiply

mass of C9H8O4 = 180.2 × 2/ 138.1

mass of C9H8O4 = 360.4 /138.1

mass of C9H8O4 = 2.60970311369

mass of C9H8O4  = 2.61 g