in an experiment, 2.50g of salicylic acid is reacted with 10.31g of methanol. the yield of methyl salicylate, C8H8O3, is 1.27g. what is the percentage yield?

This is a limiting reagent problem. I know that because amounts for BOTH reactants are given.

Write and balance the equation.
Convert 2.50 g SA to mols. mol = g/molar mass
Do the same for methanol.
Using the coefficients in the balanced equation, convert mols SA to mols of the product.
Do the same for mols methanol.
It is quite likely that the two values for mols of the product will not be the same which means one of them is wrong. The correct value in limiting reagent problems is ALWAYS the smaller value and the reagent producing that value is the limiting reagent.
Use the smaller value and convert to grams. g = mol x molar mass. This is the theoretical yield (TY). The actual yield (AY) is 1.27 g from the problem.
% yield = (AY/TY)*100 = ?

46.4%

92.6

To calculate the percentage yield, you need to compare the actual yield of the desired product (methyl salicylate) to the theoretical yield. The theoretical yield is the amount of product that would be formed if the reaction went to completion based on the limiting reactant.

To find the theoretical yield, you need to determine the limiting reactant first. The limiting reactant is the reactant that is completely consumed in the reaction, thus limiting the amount of product that can be formed.

To find the limiting reactant, you can use the molar masses of salicylic acid and methanol.

The molar mass of salicylic acid (C7H6O3) can be calculated as follows:
C: 7 atoms x 12.01 g/mol = 84.07 g/mol
H: 6 atoms x 1.01 g/mol = 6.06 g/mol
O: 3 atoms x 16.00 g/mol = 48.00 g/mol
Total: 138.13 g/mol

The molar mass of methanol (CH3OH) is:
C: 1 atom x 12.01 g/mol = 12.01 g/mol
H: 4 atoms x 1.01 g/mol = 4.04 g/mol
O: 1 atom x 16.00 g/mol = 16.00 g/mol
Total: 32.05 g/mol

Next, you need to calculate the number of moles for each reactant using their respective masses and molar masses.

Number of moles of salicylic acid = Mass of salicylic acid / Molar mass of salicylic acid
Number of moles of salicylic acid = 2.50 g / 138.13 g/mol

Number of moles of methanol = Mass of methanol / Molar mass of methanol
Number of moles of methanol = 10.31 g / 32.05 g/mol

Now, you can determine the stoichiometry of the reaction by comparing the balanced equation for the reaction:

Salicylic acid + Methanol → Methyl salicylate + Water

The stoichiometric ratio of salicylic acid to methyl salicylate is 1:1, meaning that for every 1 mole of salicylic acid, 1 mole of methyl salicylate is produced. Therefore, the number of moles of methyl salicylate formed is equal to the number of moles of salicylic acid.

Now, you can calculate the theoretical yield of methyl salicylate in grams using the number of moles of salicylic acid and its molar mass:

Theoretical yield of methyl salicylate = Number of moles of salicylic acid x Molar mass of methyl salicylate
Theoretical yield of methyl salicylate = (2.50 g / 138.13 g/mol) x 152.15 g/mol

Finally, you can calculate the percentage yield using the actual yield and the theoretical yield:

Percentage yield = (Actual yield / Theoretical yield) x 100
Percentage yield = (1.27 g / Theoretical yield) x 100

Now, substitute the value of the theoretical yield into the formula to obtain the percentage yield.