Question

determine percent yield of each isomer. (the weight of the other isomer is the difference between the mass of the product and the mass of the starting material..) we weighed out .2 g of maleic acid. added .3 ml of water and .25ml of HCL. then refluxed gently for 30mins. cooled and collected solid product by vacuum filtration using hirsch funnel then recrystallized using hot solvent and air dried. the only data i have taken down is mass starting material (maleic acid): .208 g crude material: .136g mass end material: .024g how would you determine the percent yield of maleic and fumaric acid?

Answer 1

The isomerization reaction is shown below and HCl act as catalyst and the stoichiometry between maleic acid and fumaric acid is 1:1

Sarting material, Maleic acid = 0.208 g

Number of moles of Maleic acid = weight/molacular weight = 0.208/ 116.07 = 0.0018 moles

If the reactions is completed ( i.e. yield is 100%), it should give 0.0018 moles of furmaric acid (0.208 g) as the stoichiometry between maleic acid and fumaric acid is 1:1 as shown by above reaction.

But here you got , 0.024 g as end material.

so, Fumaric acid produced is only 0.024 g (assuming product is highly pure).

So, yield of the Fumaric acid isomer = (0.024/0.208)*100 = 11 %

The yield of other isomer(Maleic acid) whis is a unreacted starting metrial is = 100% -11% = 89%.