Question

Aspirin is prepared by reaction of salicylic acid (C7H6O3) with acetic anhydride (C4H6O3)according to the following equation:

C7H6O3Salicylicacid+C4H6O3Aceticanhydride→C9H8O4Aspirin+CH3COOHAceticacid

a. How many grams of acetic anhydride are needed to react with 3.07 g of salicylic acid?
b. How many grams of aspirin will result?
c. How many grams of acetic acid are formed as a by-product?

Answer 1

For a: The mass of acetic anhydride reacts is 2.25 grams

For b: The mass of aspirin produced is 3.96 grams

For c: The mass of acetic acid produced is 1.32 grams

Step-by-step explanation:

To calculate the number of moles, we use the equation:

`\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}` .....(1)

Given mass of salicylic acid = 3.07 g

Molar mass of salicylic acid = 138.12 g/mol

Putting values in equation 1, we get:

`\text{Moles of salicylic acid}=(3.07g)/(138.12g/mol)=0.022mol`

The chemical equation for the reaction of salicylic acid and acetic anhydride follows:

`C_7H_6O_3+C_4H_6O_3\rightarrow C_9H_8O_4+CH_3COOH`

• For a:

By Stoichiometry of the reaction:

1 mole of salicylic acid reacts with 1 mole of acetic anhydride

So, 0.022 moles of salicylic acid will react with =
`(1)/(1)* 0.022=0.022mol` of acetic anhydride

Now, calculating the mass of acetic anhydride from equation 1, we get:

Molar mass of acetic anhydride = 102.1 g/mol

Moles of acetic anhydride = 0.022 moles

Putting values in equation 1, we get:

`0.022mol=\frac{\text{Mass of acetic anhydride}}{102.1g/mol}\\\\\text{Mass of acetic anhydride}=(0.022mol* 102.1g/mol)=2.25g`

Hence, the mass of acetic anhydride reacts is 2.25 grams

• For b:

By Stoichiometry of the reaction:

1 mole of salicylic acid produces 1 mole of aspirin

So, 0.022 moles of salicylic acid will produce =
`(1)/(1)* 0.022=0.022mol` of aspirin

Now, calculating the mass of aspirin from equation 1, we get:

Molar mass of aspirin = 180.16 g/mol

Moles of aspirin = 0.022 moles

Putting values in equation 1, we get:

`0.022mol=\frac{\text{Mass of aspirin}}{180.16g/mol}\\\\\text{Mass of aspirin}=(0.022mol* 180.16g/mol)=3.96g`

Hence, the mass of aspirin produced is 3.96 grams

• For c:

By Stoichiometry of the reaction:

1 mole of salicylic acid produces 1 mole of acetic acid

So, 0.022 moles of salicylic acid will produce =
`(1)/(1)* 0.022=0.022mol` of acetic acid

Now, calculating the mass of acetic acid from equation 1, we get:

Molar mass of acetic acid = 60 g/mol

Moles of acetic acid = 0.022 moles

Putting values in equation 1, we get:

`0.022mol=\frac{\text{Mass of acetic acid}}{60g/mol}\\\\\text{Mass of acetic acid}=(0.022mol* 60g/mol)=1.32g`

Hence, the mass of acetic acid produced is 1.32 grams