Recrystallization - finding the amount of the final product of Cmpd A

In summary: You have 20 mL of ethanol, so you will have 20 mL * 0.08 g/mL = 1.6 g of compound A left in the solution. So you will have 10.4 g - 1.6 g = 8.8 g of compound A as the final product.In summary, after recrystallization of the sample using 20mL of ethanol, the final product should be approximately 8.8 g of compound A, with a percent recovery of (8.8 g / 11.0 g) x 100 = 80%.
  • #1
bluenarwhals
8
0

Homework Statement


Compound A
mass - 11.0g
solubility in ethanol at 78 deg C - 0.53 g/mL
solubility in ethanol at 0 deg C - 0.08 g/mL

Impurity B
mass - 2.5 g
solubility in ethanol at 78 deg C - 0.82 g/mL
solubility in ethanol at 0 deg C - 0.12 g/mL

Impurity C
mass - 2.5 g
solubility in ethanol at 78 deg C - insoluble
solubility in ethanol at 0 deg C - insoluble

The sample is recrystallized using 20mL of ethanol. It is boiled with 20mL of ethanol, filtered by gravity and then cooled in ice and filtered by suction. How much compound A should be obtained as the final product?

Homework Equations



Percent recovery = pure mass / crude mass x 100

The Attempt at a Solution



0.53 g/mL. 20 mL of ethanol. totals to 10.4 g.
2.5 g is insoluble due to Impurity C

Honestly, I do not know where to start as it feels like I am missing one piece of essential information.
 
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  • #2
bluenarwhals said:
0.53 g/mL. 20 mL of ethanol. totals to 10.4 g.

And that's almost the final answer. You should just take into account amount that was left dissolved in ethanol.

Mass of the recrystallized solid will be higher (because of the presence of B), but question doesn't ask for the mass of solid after recrystallization, but for the mass of compound A. Can be just a lousy wording though.
 
  • #3
10.4 g. The amount that was left dissolved in ethanol? Do you mean the 0.08 g? I'm not exactly sure what you're saying. Thanks for answering.
 
  • #4
0.08 g per mL of ethanol - this is what is left in the solution after recrystallization (and it is lost with the ethanol that you are throwing out).
 
  • #5
The amount of Compound A obtained as the final product will depend on the efficiency of the recrystallization process and the solubility of Compound A and its impurities at different temperatures. Without knowing the solubility of Compound A at 0 degrees Celsius and the efficiency of the recrystallization process, it is impossible to accurately calculate the amount of Compound A obtained. Additionally, the information provided does not specify the percentage of Compound A in the original sample, which would also affect the final amount obtained.

In order to accurately determine the amount of Compound A obtained as the final product, more information is needed, such as the percentage of Compound A in the original sample, the solubility of Compound A at 0 degrees Celsius, and the efficiency of the recrystallization process. Without this information, it is not possible to provide a precise answer.
 

FAQ: Recrystallization - finding the amount of the final product of Cmpd A

How does recrystallization work to find the amount of the final product of Cmpd A?

Recrystallization is a process used in chemistry to purify a solid compound by dissolving it in a solvent and then allowing it to cool and crystallize. By carefully controlling the conditions of the recrystallization, impurities can be removed from the compound, leaving behind a purer final product. The amount of the final product can be determined by measuring the mass of the crystals obtained after the recrystallization process.

What factors can affect the efficiency of recrystallization for determining the amount of the final product of Cmpd A?

The efficiency of recrystallization can be affected by several factors, including the choice of solvent, the temperature at which the compound is dissolved and cooled, and the rate of cooling. The solubility of the compound in the solvent and the solubility of any impurities in the solvent can also impact the efficiency of the process.

Is it necessary to use a specific type of solvent for recrystallization when determining the amount of the final product of Cmpd A?

It is important to choose a solvent in which the compound has a high solubility at high temperatures and a low solubility at low temperatures. This allows for the compound to be easily dissolved at high temperatures and then precipitated out of solution at low temperatures, resulting in a purer final product. The solvent should also be relatively non-toxic and easy to remove from the final product.

Can recrystallization be used for all types of compounds to determine the amount of the final product of Cmpd A?

Recrystallization is a commonly used technique for purifying solid compounds, but it may not be suitable for all types of compounds. Some compounds may decompose or react with the chosen solvent, making recrystallization ineffective. In these cases, alternative purification methods may need to be used to determine the amount of the final product.

How can the yield of the final product be calculated after recrystallization is complete?

The yield of the final product can be calculated by dividing the mass of the purified compound obtained after recrystallization by the initial mass of the compound used. This value can then be multiplied by 100 to obtain a percentage yield. It is important to note that the yield may be affected by losses during the recrystallization process, such as through filtration or transfer of the crystals.

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