I asked this already but for some reason the answer I got isnt being accepted online
Question:
In the laboratory, 3.50 grams of salicylic acid were reacted with 7.20 ml of acetic anhydride (density equal to 1.08 g/ml). Determine the limiting reagent.
I did:
salicylic acid + acetic anhydride → acetyl salicylic acid + acetic acid
C6H4(OH)COOH + (CH3CO)2O → CH3COOC6H4COOH + CH3COOH
moles C6H4(OH)COOH = (mass C6H4(OH)COOH) / (mole mass C6H4(OH)COOH)
moles C6H4(OH)COOH = (3.50 g) / (138.12354 g/mol)
moles C6H4(OH)COOH = 0.025396 mol
density (CH3CO)2O = [mass (CH3CO)2O] / [volume (CH3CO)2O]
or
mass (CH3CO)2O = [density (CH3CO)2O][volume (CH3CO)2O]
mass (CH3CO)2O = [1.08 g/mL][7.20 mL]
mass (CH3CO)2O = 7.776 g
moles (CH3CO)2O = [mass (CH3CO)2O] / [mole mass (CH3CO)2O]
moles (CH3CO)2O = [7.776 g] / [102.09024 g/mL]
moles (CH3CO)2O = 0.0761679 mol
So the answer would be salycic acid b/c its the lower number 0.025 mol
BUT my answer is incorrect apparently. Is here something I did wrong?
Thanks for showing your work.
Nope. You're right on target and your numbers are correct. Salicylic acid is the limiting reagent. One of several things may be the problem.
1. You posted the wrong numbers.
2. You didn't post all of the problem.
3. The reaction you have is wrong.
4. The problem was given to you with the wrong numbers.
5. The database (key) is wrong.
But I can assure you that if the numbers you posted are correct and the equation is correct, then the limiting reagent is salicylic acid. In MOST of the aspirin problems the acetic anhydride is the limiting reagent but that isn't true here.
Based on the calculations you provided, the number of moles for salicylic acid is indeed 0.025 mol, and the number of moles for acetic anhydride is 0.0761679 mol. Based on these values, it appears that your answer of salicylic acid being the limiting reagent is correct.
However, there could be other factors at play that may have resulted in your answer being marked as incorrect. Here are a few possibilities to consider:
1. Mathematical Accuracy: Double-check your calculations to make sure there are no rounding errors or miscalculations in the values you obtained. Even a small mistake in one of the steps can lead to a different final answer.
2. Stoichiometry: Confirm if the balanced chemical equation you used accurately represents the stoichiometry of the reaction. If the stoichiometry is incorrect, it could impact the determination of the limiting reagent.
3. Assumptions: Check if any assumptions were made that could affect the validity of the answer. For example, if there is any additional information or condition given in the problem that you missed or overlooked, it could change the outcome.
4. Answer Format: Consider if there are any specific requirements or conventions for expressing the answer in the particular online platform. Sometimes, the format or units of the answer can affect its acceptance.
If after reviewing these factors you still believe your answer is correct, it may be helpful to consult with your instructor or refer to the specific guidelines provided by the online platform to determine why your answer is not being accepted.