Sodium Benzoate And Hydrochloric Acid

Abstract:

This experiment demonstrated the effect of acidity to promote protonation in a chemical reaction. Sodium benzoate and hydrochloric acid was mixed to evaluate if the chemical reaction moved to the right or left. Due to a change in pH, the protonation of sodium benzoate produced an appropriate amount of benzoic acid as a product. To retrieve it, a vacuum filtration and recrystallization process was completed. The melting point range of the final product was precise and accurate to the literature measurement of benzoic acid, indicating its purity. The final product had a percent yield of 74%.

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Introduction:

The pH of a substance decides what will happen

The use of water as a solvent gave a high yield because of its high solubility in high temperature and low solubility in low temperature. This explains the process of boiling and placing in an ice bath during recrystallization. Figure 3. Physical information pertaining to sodium benzoate.

Chemical compounds Exact weight (grams) pH (with solution) Physical observations sodium benzoate 2.15 1.3 White powder; clumps up easily

Once the crude product had dried completely, the melting point was taken. Sodium benzoate and benzoic acid had extremely different melting points so it was simple to determine what the final product was (Figure 4). The final product had corrected melting point ranges that accurately matched benzoic acid (Figure 5). The corrected melting point equation used was: y = 0.995x – 0.304

Attempts Corrected Final product melting point (ºC) Final product melting point (ºC)

1 122.7-123.7

10 mL of deionized water was added and stirred until fully dissolved. 5.0 mL of 3.0 M of hydrochloric acid was slowly pipetted into the mixture and stirred. The pH was checked to be less than two. The solution was placed into an ice bath to decrease the temperature to 10°C. A vacuum filtration apparatus was built with an Erlenmeyer flask with a vacuum arm and connected to a vacuum source and secured for safety using a ring hoop. The cooled mixture was funneled through, and the solids remained on the top. After being washed by iced water, the crude material was observed and stored for later