I have a lab dis monday .. plz someone help .. Lab Title is

(( Recrystallization of a Solid ))

Pre-Lab Questions....

Explain the purpose of the following in this experiment.

a) using hot filtration

b) not cooling (chilling) the hot filtered solution immediately

c) washing the crystals in the final step with ice cold water

d) using gravity filtratoin ( not vacuum filration) in the hot filtration step

e) using a stemless funnel in the hot filration step

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in the experiment we have to determine the MP ( literature value 114 C ) ... and percent mass recovery of acetanilide in the orginal mixture ..

ANY clue how to approach to dese problems.. or is dere any kind of formula .. ot steps ..

Thnks for ur help in advance

REally appreciate ur help ..

thnks again

Not knowing what you are crystallizing or the procedure you are using, the following is the best I can do as far as guessing at the answers.

a) using hot filtration
You want as much of the solid as possible to go through with the filtrate. If it's the solute you are trying to separate from some solid material then it is the filtrate you don't want to lose. If it's the solute you are trying to get rid of then you don't want it crystallizing before you can separate it.

b) not cooling (chilling) the hot filtered solution immediately
I'm not sure what you are filtering an with what.

c) washing the crystals in the final step with ice cold water
You don't want the solid to dissolve during the washing procedure. Dissolution of the solid will cause the yield (percent recovery) to decrease.

d) using gravity filtration ( not vacuum filtration) in the hot filtration step
Vacuum filtration will cool the solution and you want to avoid that.

e) using a stemless funnel in the hot filtration step
Crystals may form in the stem of the funnel. If that happens the filtration step stops.

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in the experiment we have to determine the MP ( literature value 114 C ) ... and percent mass recovery of acetanilide in the original mixture ..
%recovery = (mass recovered/mass initially)*100 = ??
By the way, your English and capitalization and the use of punctuation marks is very good; too made that "dis" and "dese" slipped into the question.

By the way...... too made (I meant too bad) that "dis" and "dese" slipped into the question.

a) Using hot filtration: Hot filtration is used to remove impurities that are insoluble in the hot solvent. By heating the solution, the solute will dissolve, but any impurities that are insoluble in the hot solvent will remain behind and can be filtered out. This is done to obtain a pure solid product.

b) Not cooling (chilling) the hot filtered solution immediately: If the hot filtered solution is cooled immediately, the solute may start to crystallize out while still in solution, resulting in the formation of small crystals. This can lead to a lower yield and impure crystals. Allowing the solution to cool slowly or at room temperature before chilling promotes the formation of larger, more pure crystals.

c) Washing the crystals in the final step with ice-cold water: Washing the crystals with ice-cold water helps to remove any remaining impurities that may be present on the surface of the crystals. Ice-cold water is used to minimize any solubility of the crystals in water and to maintain the purity of the final product.

d) Using gravity filtration (not vacuum filtration) in the hot filtration step: Gravity filtration is used instead of vacuum filtration in the hot filtration step to prevent the crystallization of the solute on the filter paper and to maintain a higher yield. Vacuum filtration can cause the solution to cool quickly, leading to the premature crystallization of the solute before it passes through the filter paper.

e) Using a stemless funnel in the hot filtration step: A stemless funnel is used in the hot filtration step to prevent the solution from cooling too quickly. The stemless funnel provides a larger surface area for heat dissipation and allows for a more controlled filtration process.

To approach the problems of determining the melting point and percent mass recovery of acetanilide in the original mixture, you can follow these steps:

1. Perform the recrystallization process as outlined in the lab procedure.
2. Once you have obtained the pure acetanilide crystals, dry them thoroughly to remove any remaining solvent.
3. Determine the melting point of the pure acetanilide crystals using a melting point apparatus or a melting point capillary tube. Compare the obtained melting point with the literature value of 114°C to assess the purity of the crystals.
4. To calculate the percent mass recovery, weigh the final purified acetanilide crystals and divide it by the initial mass of the impure mixture. Multiply the result by 100 to obtain the percentage.

Remember to record all your observations and measurements accurately during the experiment. Good luck!

a) Using hot filtration:

The purpose of using hot filtration in this experiment is to remove any insoluble impurities from the solid during recrystallization. Hot filtration is performed by heating the mixture to a suitable temperature, allowing the solid to dissolve, and then filtering the hot solution to separate it from the impurities. This is done to obtain a pure solid product.

To perform hot filtration, follow these steps:
1. Set up a filtration apparatus, including a funnel and filter paper.
2. Heat the mixture in a suitable container until it reaches its boiling point.
3. Slowly pour the hot mixture into the filter funnel, ensuring the liquid passes through the filter paper while the solid remains behind.
4. Collect the filtrate in a separate container.

b) Not cooling (chilling) the hot filtered solution immediately:
The purpose of not cooling the hot filtered solution immediately is to allow the desired compound to recrystallize slowly. If the solution is cooled quickly, the crystals may form too rapidly and trap impurities within the crystal lattice, leading to impure crystals.

To prevent fast cooling, follow these steps:
1. After the hot filtration, let the filtered solution cool naturally at room temperature.
2. Do not place the solution in a refrigerator or use any external cooling sources.

c) Washing the crystals in the final step with ice-cold water:
The purpose of washing the crystals with ice-cold water is to remove any residual impurities and soluble contaminants that may be attached to the crystal surface. Ice-cold water helps to minimize the solubility of the impurities, allowing for a more effective wash.

To wash the crystals with ice-cold water, follow these steps:
1. Prepare a beaker or container with ice-cold water.
2. Carefully transfer the crystals into the cold water and gently stir or swirl to wash them.
3. Let the crystals settle, and then decant or filter off the wash water.

d) Using gravity filtration (not vacuum filtration) in the hot filtration step:
The purpose of using gravity filtration instead of vacuum filtration in the hot filtration step is to prevent the crystallization of the compound during the filtration process. Vacuum filtration may cause the solvent to evaporate quickly, leading to premature crystallization on the filter paper, which can result in poor recovery of the desired compound.

To perform gravity filtration, follow these steps:
1. Set up a filtration apparatus, including a funnel and filter paper.
2. Place a clean flask below the funnel to collect the filtrate.
3. Wet the filter paper with a small amount of the solvent before pouring the hot mixture into the funnel.
4. Allow the liquid to pass through the filter paper under the force of gravity.

e) Using a stemless funnel in the hot filtration step:
The purpose of using a stemless funnel in the hot filtration step is to prevent clogging or trapping of the solid particles during filtration. A stemless funnel allows for better flow and avoids any blockages that could compromise the separation of the solid and liquid phases.

To use a stemless funnel, follow these steps:
1. Select a stemless funnel appropriate for the volume of the mixture being filtered.
2. Ensure the stemless funnel is clean and dry before use.
3. Place the stemless funnel in the filtration apparatus, securely fitting it into the funnel holder or stand.
4. Proceed with the hot filtration process as described earlier.

For determining the melting point (MP) and the percent mass recovery of acetanilide in the original mixture, follow the specific procedures outlined in your lab manual or provided by your instructor. It is important to carefully follow the experimental steps to obtain accurate results.