Effect of pH ona food preservative

Topics: Benzoic acid, Sodium benzoate, Solubility Pages: 3 (683 words) Published: December 12, 2013
September 10th, 2013

The purpose of this experiment was to investigate a competitor’s claim that the food preservative, sodium benzoate (C6H5COONa), made by Fresh Foods International (FFI), changed into a new substance in stomach acid. Stomach acid has a pH between 1 and 3 due to the hydrochloric acid content. Based on the net equation given in the book as well as the solubility of the product our hypothesis is that a new substance will form. Net reaction: C6H5COONa(aq) + HCl(aq)  C6H5COOH(s) + NaCl(aq)

Upon completion of this experiment students will gain experience using common extraction techniques such as vacuum filtration, as well as familiarity with common calculations used in chemistry, such as mass measurements and percent yield. Description of Procedure:

2.00 g of sodium benzoate was dissolved in 10.0 mL of H2O. 7.0 mL of HCl was added to the solution and a pH of 2 (similar to stomach acid) was reached. Upon addition of the HCl, a white precipitate formed. The mixture was cooled in an ice bath until a temperature of 10 degrees Celsius was obtained to reduce solubility further. Using vacuum filtration the solid precipitate was extracted from the mixture. To allow the solid precipitate sufficient time to dry mass of the substance was obtained one week later and was found to be 1.59g. Trace amounts of the solid precipitate were lost during transfer as they stuck to the stir stick and beaker. Data, Calculations and results:

.007L * (3mol HCl)/L * (1mol C6H5COOH)/1mol HCl =0.0210 moles C6H5COOH 2.00g C6H5COONa * (1mol C6H5COONa)/(144.1g)* (1mol C6H5COOH)/(1 mol C6H5COONa) =0.0139 moles C6H5COOH Limiting Reactant: C6H5COONa

Theoretical Yield: 0.0139 mol C6H5COOH*122.1g/ mol C6H5COOH = 1.70 g mol C6H5COOH mol C6H5COOH Actual Yield: 1.59g C6H5COOH
Percent Yield: (1.59g/1.70g)*100 = 93.5%

Based on the net equation listed in...
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