Can somebody point out the step i have to take to solve this problem. It would be much appreciated. Thanks a lot!!!!
_____________________________________________________________________________________________________________________
Asprin, C9H8O4, is prepared by reacting salicylic acid, C7H6O3, with acetic anhydride, C4H6O3, in the reaction:
C7H6O3 + C4H6O3 ---> C9H8O4 + C2H4O2
A student is told to prepare 45.0 g asprin. She is also told to use a 55% excess of acetic anydride and to expect to get an 85% yeild in the reaction. How many grams of each reactant should she use?
Balance the equation.
consider a mass of 55(1/.85) g of aspiring as the product, determine the moles of aspirin. Using the coefficents, determine the moles of each reactant, and for the acetic anydride, multiply it by 1.55
ok thanks!!
wait isn't the equation already balanced?
To solve this problem, we can break it down into steps:
Step 1: Determine the molar masses of each compound
The molar mass of salicylic acid (C7H6O3) is:
7 * atomic mass of carbon + 6 * atomic mass of hydrogen + 3 * atomic mass of oxygen
The molar mass of acetic anhydride (C4H6O3) is:
4 * atomic mass of carbon + 6 * atomic mass of hydrogen + 3 * atomic mass of oxygen
The molar mass of aspirin (C9H8O4) is:
9 * atomic mass of carbon + 8 * atomic mass of hydrogen + 4 * atomic mass of oxygen
Step 2: Calculate the theoretical yield of aspirin
The theoretical yield of aspirin is the amount that would be obtained if the reaction goes to completion. It can be calculated using the stoichiometry of the reaction. From the balanced equation, we see that 1 mole of salicylic acid reacts with 1 mole of acetic anhydride to produce 1 mole of aspirin. So, the theoretical yield can be calculated by converting the given mass of aspirin to moles and then moles to grams using the molar mass of aspirin.
Step 3: Calculate the mass of reactants required
To calculate the mass of reactants required, we need to take into account the excess of acetic anhydride and the expected yield of the reaction. We will assume that the yield is 85% of the theoretical yield.
To determine the mass of salicylic acid required, we use the mole ratio from the balanced equation. For every 1 mole of salicylic acid, we need 1 mole of acetic anhydride. From this information, we can write an equation:
(mass of salicylic acid) / (molar mass of salicylic acid) = (mass of acetic anhydride) / (molar mass of acetic anhydride)
Since the acetic anhydride is given in excess (55% excess), we need to multiply the calculated mass of acetic anhydride by 1.55.
Step 4: Calculate the mass of each reactant
Using the equation from Step 3, we can solve for the mass of salicylic acid and acetic anhydride. Remember to include the 85% yield factor in the calculation.
Step 5: Verify the results
To verify the calculated masses, we can add them up and check if they match the desired total mass of 45.0 g. If they do not match exactly, there may be rounding errors or errors in the calculation. In such cases, adjust the masses slightly and re-calculate.
By following these steps, you should be able to determine how many grams of each reactant the student should use to prepare 45.0 g of aspirin with a 55% excess of acetic anhydride and an 85% yield.