Crystallization of Benzoic Acid

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In summary, the conversation discusses the preparation of a pre-lab for a lab experiment. The main question is whether to include the # moles and density of reagents, specifically 2 g of crude benzoic acid and water. The person asking the question is unsure about converting the crude benzoic acid to # moles due to impurities and also about including water since the amount needed is uncertain. They also inquire about using a density of 1 g/mL for water and 1.32 g/mL for solid benzoic acid, as none were given in the lab manual. Another person suggests using "maximum number of moles" for benzoic acid to clarify its impure state.
  • #1
thE3nigma
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Hi there,

This may seem like weird question, but for my pre-lab this week I need to add along with intro and flow chart a table of reagents. now my only two reagents that I will be using is 2 g of crude Benzoic acid (including impurities) and water. in my table though, they ask for the # moles and density of applicable.

since my 2 grams of crude benzoic acid is not pure, should I still convert it into # moles. My thinking is that I should not. Also for water, since I do not know exactly how much I will have to add during the boiling process, I believe I should not add this either.

As for densities, since none were given in the lab manual - is it customary to use 1 g/mL for water and 1.32 g/mL for benzoic acid in its solid form?

Thanks.
 
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  • #2
I would convert benzoic to moles stating something like "maximum number of moles" to underline that it is not really true.
 
  • #3
That is what I was thinking should have been done. Thanks for the tip Borek.
 

What is the purpose of crystallization in the purification of Benzoic Acid?

Crystallization is used to purify Benzoic Acid by separating it from impurities. As Benzoic Acid has a higher solubility in hot solvent compared to cold solvent, it can be dissolved in hot solvent and then allowed to cool and form crystals. This process helps to remove impurities that may have been dissolved in the hot solvent, leaving behind pure Benzoic Acid crystals.

What factors affect the rate of crystallization of Benzoic Acid?

The rate of crystallization of Benzoic Acid can be affected by factors such as temperature, solvent choice, and agitation. Higher temperatures can speed up the process, while agitation can help to create more nucleation sites for crystals to form. Choosing the right solvent is also important as it should have a high solubility for Benzoic Acid at high temperatures, but low solubility at lower temperatures.

How do you determine if the crystallization of Benzoic Acid is successful?

The success of crystallization can be determined by measuring the purity and yield of the resulting crystals. A high purity and yield indicate a successful crystallization process. Additionally, the crystals should have a defined shape and be free of impurities, indicating that they have been separated from the impurities during the process.

What are the potential sources of error in the crystallization of Benzoic Acid?

Potential sources of error in the crystallization process include using the wrong solvent, not allowing enough time for the solvent to cool and crystals to form, and not filtering the crystals properly. Other factors such as temperature fluctuations, impurities in the starting material, and inadequate stirring can also affect the success of the process.

Can the same process be used to crystallize other organic compounds?

Yes, the process of crystallization can be used to purify and separate other organic compounds. However, the specific conditions such as temperature, solvent choice, and agitation may vary depending on the compound. It is important to optimize the process for each compound to achieve the best results.

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