[purplemonkey123]

If 1.20 grams of salicylic acid is reacted with excess methanol, what mass of ester should you expect to achieve theoretically?

Molar masses of..
salicylic acid is 138.13g/mol
methanol is 32.05g/mol
ester (methyl salicylate) is 152.16g/mol

Mole ratio
1:1

My work:
1. 1.20 g salicylic acid (1 mol salicylic acid/138.13 g salicylic acid) = 0.008687468 mol salicylic acid

2. 0.008687468 mol salicylic acid (1 mol ester/1 mol salicylic acid) = 0.008687468 mol ester

3. 0.008687468 mol ester (152.16 g ester/1 mol ester) = 1.32 g ester


so 1.32g of ester would be expected.

Is my work correct? or do I have to use the excess reagent to find the mass of the product?

[Corribus]

Approach is correct. Since they specified excess methanol, salicylic acid is understood to be the limiting reagent.

[Borek]

In other words - stoichiometry for organic reactions is not different from stoichiometry in general, exactly the same rules apply.

On some general level the only real difference between inorganic and organic reactions is that organic reactions rarely go to completion (more precisely - their equilibrium constants are typically orders of magnitude lower than equilibrium constants for inorganic reactions). Thus it is nothing strange to have yields like 99.99% in inorganic preparative chemistry (thats what makes them suitable for the gravimetric analysis), while typical yield in organic chemistry will be something between 40-80% (as a rule of thumb subtract 10% from the yield reported in the literature ).