[cyberdx16]

Calculate the theoretical mass of aspirin that would have been obtained from the reaction of 1.10 g of salicylic acid with an excess of acetic anhydride.

I am only given one value of mass, wouldnt i need to know the mass of acetic anhydride? or when they say excess, does it mean that the ratio of salicylic acid and acetic anhydride is 1:1?

[enahs]

When they say excess they mean excess.
Or that the other is the limiting reagent.

Or
A + B -> C

If B is in excess, it means you get to completely use up all of A.

[cyberdx16]

so would this be correct, find the molar value of chem A and chem B, then divide Chem B over Chem A which will give me my ratio. then take this value and mutiply it by the molar value of chem B which will give me my weight value of Chem B. Add weight of Chem A and Chem B and that should give me my theoretical mass of aspirin?

[enahs]

First, write a balanced equation (even if you do not do it here).

Is the molar ratio 1:1?

Because you know salicylic acid is the limiting reagent, the amount(in mol's) of the salicylic acid is the maximum possible amount (in mol's) of the product (in a 1:1 reaction, is this reaction 1:1?). Therefor if you assume a 100% complete reaction, the amount of salicylic acid (in mols) = maximum possible amount of acetyl salicylic acid (in mols) [aspirin].

In short, but you really should understand why.
Calculate mols of salicylic acid, relate that with mols of aspirin; convert mols of aspirin to grams. You are done. It is just one division and one multiplication.

[cyberdx16]

First, write a balanced equation (even if you do not do it here).

Is the molar ratio 1:1?

Because you know salicylic acid is the limiting reagent, the amount(in mol's) of the salicylic acid is the maximum possible amount (in mol's) of the product (in a 1:1 reaction, is this reaction 1:1?). Therefor if you assume a 100% complete reaction, the amount of salicylic acid (in mols) = maximum possible amount of acetyl salicylic acid (in mols) [aspirin].

In short, but you really should understand why.
Calculate mols of salicylic acid, relate that with mols of aspirin; convert mols of aspirin to grams. You are done. It is just one division and one multiplication.

Thx a lot, i dont remember anything from first semester chem