Question

calculate the cost/gram of crude and recrystallized product for the reaction given the following: salycylamide ($0.38/g); NaI ($0.78/G); 6% (W/V) NaOCl ($1.34/l); sodium thiosulfate ($10.16/L); ethanol (absolute and 95%) ($11.17/L).You can ignore the cost of 10% HCl since the amount used was not determined accurately and it is dirt cheap. The product you made is not readily available from commercial suppliers so we could have to conclude this reaction is economically feasible!

Answer 1

To answer this question it is important to know an experimental procedure extracted the web:

"Measure out ~1.0 g of salicylamide and record the mass to the nearest 0.1 g. Place the salicylamide into a 100-mL round-bottom flask. Dissolve the salicylamide in 20 mL of absolute ethanol, warming the flask with your hand to speed up the dissolution. Once the salicylamide is completely dissolved, add 1.2 g of sodium iodide (NaI) to the reaction mixture, stirring with a glass stirring rod until the solution is homogeneous. Place the 100-mL round-bottom containing the reaction mixture into an ice bath. (Think about thermal contact!! Ice bath means ice AND water.) When the reaction is cooled to 0 ˚C (about 5 minutes), remove the reaction vessel from the ice bath and quickly add 9.2 mL of 6% (w/v) sodium hypochlorite solution (ultra strength household bleach). Swirl the flask vigorously to completely mix the contents. The solution will change colors from the initial clear reaction mixture to a dark red-brown to increasingly lighter shades of yellow. When the solution reaches a faint, pale yellow color, the reaction is complete. (Typically, this takes less than five minutes.) Allow the reaction vessel to sit on the benchtop undisturbed for 10 minutes. Add 10 mL of a previously prepared solution of 10% (w/v) sodium thiosulfate to the reaction solution and swirl the flask until the contents are thoroughly mixed. Next, acidify Lab Documentation, p.4 the reaction solution by slowly adding 10% HCl. Monitor the acidity of the solution using litmus paper. You will notice a white solid beginning to form in the reaction vessel. At this point, the pH of the solution is near the desired acidity. Continue adding 10% HCl, but carefully monitor the acidity. Once the mixture is acidic, filter using vacuum filtration and a Büchner funnel. Collect the precipitate from the filter paper and recrystallize from 95% ethanol. (After the recrystallization mixture has cooled to room temperature, place it an ice bath for ~15 minutes to complete crystallization.) Filter using vacuum filtration and allow the crystals to remain on the funnel with air being drawn over them for 20 minutes to speed up the drying process."

http://www.mycrandall.ca/faculty/MSchriver/labrefs/jchemedgreeneas/JCE2008p1426wGreenEASstd.pdf

Salycylamide = $0.38/g x 1g = $0.38

NaI = $0.78/g x 1.2g = $0.94

NaOCl = $1.34/1000mL x 9.2mL = $0.01

Na₂S₂O₃ = $10.16/1000mL x 10mL = $0.10

Ethanol = $11.17/1000mL x 20mL = $0.22

Crude product = $0.38 + $0.94 + $0.01 + $0.10 + $0.22 = $1.65

We can assume that it takes 20 mL of ethanol to recrystallize the product:

Recrystallized product = $1.65 + $0.22 = $1.87