Ph of Food Preservation Discussion and Questions

Discussion

The purpose of the experiment was to evaluate if a new substance is formed when sodium benzoate is placed in an environment that stimulates stomach acid.  This was stimulated by adding 3M hydrochloric acid to the sodium benzoate until the pH was ~2. Stomach acid is an aqueous hydrochloric acid with a pH solution between the ranges of 1-3. After adding the HCl the solution changed from clear solution to a white solution and began to clump together. With constant stirring the solution became a paste like substance.

During my experiment I used unknown #2.  After calculations I achieved a 40% yield and a density of 1.25g/mL. Comparing my density to the given densities of all the unknowns I must assume my unknown was heptane as the chart shows the density of chlorobenzene is 1.11 g/mL which is the closest to my calculated density. 40% yield may have been caused by multiple errors.  For example, I did not leave my solution in the ice bath long enough, I was unable to completely extract from the walls of the vial and I had some difficulty with the vacuum filtration. I may have also not measured my mass and volume as accurately. Additionally I may have experienced pipet issues because multiple lab members were using the same pipet. Since others were using the pipet in between there may have been a mixture of my unknown with theirs causing error.  These errors most likely affected my results because the anticipated reaction may not have occurred or accomplished because my yield was 40%.

If I were to repeat this experiment I would try to ensure all my measurement are accurate as possible, leave my solution in the ice bath longer and avoid any pipet related issues.  Upon completion of the experiment as benzoic acid precipitated from the solution. My original hypothesis was that a new substance would form although taking my 40% yield into consideration I remain unsure and believe I would need to repeat the experiment in hopes that the yield would be closer to 100% and have density closer in range to the given density of chlorobenzene.