Question

1. 1. A student performed the recrystallization process that you already know. At the end of the experiment and drying the sample for 1 week, the student goes to the laboratory to be able to use some equipment and identify the compounds obtained. What is the importance of preparing the sample correctly, using the proper precautions and specificity of the equipment to be used? Do you think that this step can alter my results if I have not prepared the sample well to run it on any computer? How can this affect the integrity of the team? (example: bring a wet sample for a dry material analysis kit). 2. A student performs the synthesis of fumaric acid with 5g of maleic acid, whose molecular weight is 134.08g/mol. At the end of the synthesis the student obtains 4.27g of fumaric acid, whose molecular weight is 134.08g/ mol (it is the same value of MW). Calculate the following a. Moles of maleic acid b. Moles of fumaric acid c. Theoretical grams (stoichiometry) d. Yields (obtained / expected x 100%)

Answer 1

1) Before any identification we have to prepare sample for that. a) we have to check the yield.b) we have to check the stable condition like if it is hydroscopic then keep in closed system. c) Solubility check d) note down the colour of compound. After that we can check physical properties like melting point, boiling point, density, refractive index. After that identification lik NMR, mass ,single XRD.

2)a)mole of maleic acid = mass/mw =5/134.08= 0.0372mole

b) mole of fumaric acid =4.27/134.08 = 0.0318.

c) Theoretical yield = 5g as reactant only 5 gram.

d) % of yield = 4.27×100/5 =85.4%