Unit 4 Assignment 1
1.6 In the preparation of making paracetamol, there are many techniques used.
One of which is recrystallisation which is used to purify solid compounds. Solids are usually
more soluble in hot liquids than in cold liquids. During recrystallization, an impure solid
compound is dissolved in a very hot liquid until the solution is holding as much water as can be
absorbed, and then the liquid is allowed to cool. Slow cooling of the solution is key as it
promotes the formation of pure crystals as the molecules of the impurities that don't fit too well
have time to go back to the solution. As the crystal develops, impurities are eliminated from the
crystal lattice, and so complete the purification process. The principle behind recrystallization is
that the amount of solute which can be dissolved by a solvent increases via temperature. For
example, at a high temperature, the solute has an increased solubility in the solvent, therefore a
much smaller quantity of hot solvent is required than when the solvent is at room temperature.
This influences the purity of the paracetamol because it removes the aminophenol making the
paracetamol isolated and therefore more pure. The longer the crystals are left to cool will
produce larger crystals which are more pure.
Additionally, filtration is used in order to prepare paracetamol. This is a technique used to
separate solids from liquids. This can be done by pouring a mixture onto a membrane (filter
paper) which allows the passage of liquid, resulting in the collection of the solid. This is done by
the filter paper allowing the liquid to run through and into the beaker below and so any larger
molecules (solid) will be maintained in the paper and so can be collected. Filter paper is a
semi-permeable paper barrier placed perpendicular to a liquid or air flow. It is used to separate
fine substances from liquids or air. It is used in science labs to remove solids from liquids. This
can be used to remove sand from water. For example, this is used in step 4 where the solid is
filtered off using a Hirsch funnel filter and a vacuum pump. By filtering out the liquid, the solid
can become purer as impurities are removed, leaving the desired product behind. This will filter
out the ethanoic acid and the anhydride and keep the aminophenol and paracetamol in the
paper. This influences the synthesised paracetamol into being as pure as possible by getting rid
of the impurities. In theory, insoluble impurities can be removed from a compound easily. The
compound is dissolved in a solvent, the solution is filtered to remove the insoluble impurities,
and the solvent evaporates to produce the solid compound. The insoluble impurities are left
behind in the filter paper.
As well as filtration, the final step is drying which occurs in the dessicator. A dessicator is a
specialist type of equipment used as sealable enclosures containing desiccants which
preserves moisture sensitive things, like cobalt chloride paper. They protect chemicals which
react with water from humidity by drying them out. The interior of the desiccator is dry due to the
desiccant at the bottom and because it is sealed to keep outside, moist air from getting inside.
The purpose of drying is to keep the physico-chemical properties (meaning being physical and
chemical). of materials; ensure the preservation of materials over prolonged periods and
eliminate excess weight in shipping. Preservation is the main advantage of the drying technique,
however it is useful in influencing the purity of paracetamol by removing the water and
improving the yield of the paracetamol.
, Unit 4 Assignment 1
1.7 Techniques of chromatography and melting point are fairly accurate on estimating the purity
of paracetamol.
Chromatography techniques are good because they are simple which makes it easy and
straightforward for students to carry out in the college laboratory. Results also are produced
quickly which is effective as it keeps students intrigued in the practical they are completing -
instead of them losing interest which could occur if results were long to develop.
Chromatography is also environmentally friendly which means that it is harmless to the
environment that is beneficial as the practical can occur without a worry of affecting the
environment itself. Additionally, you can visualise impurities by comparing them to reference
samples. However, this technique can be viewed negatively because the spots are not clearly
defined which may have been due to an individual's error where too much of the sample has
been used. As well as this, chromatography does not give a percentage purity, making it more
advanced and difficult for individuals to estimate the purity of paracetamol. The technique gives
accurate results but requires a longer procedure for results to be produced. Another
disadvantage is that it cannot tell you all of the impurities present therefore the sample cannot
be scanned in too much depth. The stationary phase on the tlc plate is extremely delicate which
means that there is a risk of it breaking easily and having an effect on results. As well, there is
another risk of interference from contaminations on plates like oils and fingers.
Overall, I think that chromatography is a good technique because it does complete the
objectives of separating the substances. It does this in a quick, easy, cheap and straightforward
way which is suitable for a college laboratory. However, a method providing very imprecise
results is not accurate. To get accurate chromatographic results, a laboratory must first check
the precision of the chromatographic method. The accuracy can be affected by the absorbent,
the solvent, the chromatography plate itself, application technique and the temperature of the
solvent and plate.
Additionally, the melting point technique is good because it provides quick results and only uses
one piece of equipment in order to take place. This makes the experiment easy and
straightforward for students to carry out. No specialists are required to operate the equipment
and so more individuals can carry out the melting point technique.
1.6 In the preparation of making paracetamol, there are many techniques used.
One of which is recrystallisation which is used to purify solid compounds. Solids are usually
more soluble in hot liquids than in cold liquids. During recrystallization, an impure solid
compound is dissolved in a very hot liquid until the solution is holding as much water as can be
absorbed, and then the liquid is allowed to cool. Slow cooling of the solution is key as it
promotes the formation of pure crystals as the molecules of the impurities that don't fit too well
have time to go back to the solution. As the crystal develops, impurities are eliminated from the
crystal lattice, and so complete the purification process. The principle behind recrystallization is
that the amount of solute which can be dissolved by a solvent increases via temperature. For
example, at a high temperature, the solute has an increased solubility in the solvent, therefore a
much smaller quantity of hot solvent is required than when the solvent is at room temperature.
This influences the purity of the paracetamol because it removes the aminophenol making the
paracetamol isolated and therefore more pure. The longer the crystals are left to cool will
produce larger crystals which are more pure.
Additionally, filtration is used in order to prepare paracetamol. This is a technique used to
separate solids from liquids. This can be done by pouring a mixture onto a membrane (filter
paper) which allows the passage of liquid, resulting in the collection of the solid. This is done by
the filter paper allowing the liquid to run through and into the beaker below and so any larger
molecules (solid) will be maintained in the paper and so can be collected. Filter paper is a
semi-permeable paper barrier placed perpendicular to a liquid or air flow. It is used to separate
fine substances from liquids or air. It is used in science labs to remove solids from liquids. This
can be used to remove sand from water. For example, this is used in step 4 where the solid is
filtered off using a Hirsch funnel filter and a vacuum pump. By filtering out the liquid, the solid
can become purer as impurities are removed, leaving the desired product behind. This will filter
out the ethanoic acid and the anhydride and keep the aminophenol and paracetamol in the
paper. This influences the synthesised paracetamol into being as pure as possible by getting rid
of the impurities. In theory, insoluble impurities can be removed from a compound easily. The
compound is dissolved in a solvent, the solution is filtered to remove the insoluble impurities,
and the solvent evaporates to produce the solid compound. The insoluble impurities are left
behind in the filter paper.
As well as filtration, the final step is drying which occurs in the dessicator. A dessicator is a
specialist type of equipment used as sealable enclosures containing desiccants which
preserves moisture sensitive things, like cobalt chloride paper. They protect chemicals which
react with water from humidity by drying them out. The interior of the desiccator is dry due to the
desiccant at the bottom and because it is sealed to keep outside, moist air from getting inside.
The purpose of drying is to keep the physico-chemical properties (meaning being physical and
chemical). of materials; ensure the preservation of materials over prolonged periods and
eliminate excess weight in shipping. Preservation is the main advantage of the drying technique,
however it is useful in influencing the purity of paracetamol by removing the water and
improving the yield of the paracetamol.
, Unit 4 Assignment 1
1.7 Techniques of chromatography and melting point are fairly accurate on estimating the purity
of paracetamol.
Chromatography techniques are good because they are simple which makes it easy and
straightforward for students to carry out in the college laboratory. Results also are produced
quickly which is effective as it keeps students intrigued in the practical they are completing -
instead of them losing interest which could occur if results were long to develop.
Chromatography is also environmentally friendly which means that it is harmless to the
environment that is beneficial as the practical can occur without a worry of affecting the
environment itself. Additionally, you can visualise impurities by comparing them to reference
samples. However, this technique can be viewed negatively because the spots are not clearly
defined which may have been due to an individual's error where too much of the sample has
been used. As well as this, chromatography does not give a percentage purity, making it more
advanced and difficult for individuals to estimate the purity of paracetamol. The technique gives
accurate results but requires a longer procedure for results to be produced. Another
disadvantage is that it cannot tell you all of the impurities present therefore the sample cannot
be scanned in too much depth. The stationary phase on the tlc plate is extremely delicate which
means that there is a risk of it breaking easily and having an effect on results. As well, there is
another risk of interference from contaminations on plates like oils and fingers.
Overall, I think that chromatography is a good technique because it does complete the
objectives of separating the substances. It does this in a quick, easy, cheap and straightforward
way which is suitable for a college laboratory. However, a method providing very imprecise
results is not accurate. To get accurate chromatographic results, a laboratory must first check
the precision of the chromatographic method. The accuracy can be affected by the absorbent,
the solvent, the chromatography plate itself, application technique and the temperature of the
solvent and plate.
Additionally, the melting point technique is good because it provides quick results and only uses
one piece of equipment in order to take place. This makes the experiment easy and
straightforward for students to carry out. No specialists are required to operate the equipment
and so more individuals can carry out the melting point technique.
