Apparatus list
- Lab coat
- Safety goggles
- Safety gloves
- Lab jack
- Clamp and clamp stand
- Filter paper
- Glass funnel
- Glass beakers
- Heat bath/heating mantle
- Conical flask
- Condenser
- Distillate flask
- Thermometer
- Measuring cylinder
Diagram 1 – Gravity filtration
Diagram 2 – Distillation
Method
- Firstly, I used the gravity filtration technique to remove the charcoal from the water sample. Gravity filtration is the method of choice to remove solid impurities from an organic liquid. I poured the water into the glass beaker that had the glass funnel and filter paper in until the insoluble impurity was left behind on the filter paper and the rest of the water sample went through into the glass beaker.
- Then, I established that the insoluble impurity was removed from the water because bits of it were seen on the filter paper and before the gravity filtration was used the charcoal was seen floating at the top of the water. After using gravity filtration it was no longer seen floating at the top of the water as it had been completely removed.
- Next, I used the distillation technique to remove the sodium hydroxide and purple dye from the water sample. Distillation is a method of separating chemical substances based on differences in their volatilities in a boiling liquid mixture. The sample water was heated until it boiled and the resulting hot vapours were captured and cooled. They were then collected in a receiving flask.
- Finally, the two soluble impurities were left behind in the boiling flask and were clearly seen inside it. The collection flask was now filled with 10cm3 of purified water. Visibly I could see that it did not have the purple dye inside.
Exercise 2 – Syntheses and Use of the Vat Dye Indigo
Objective
To prepare indigo and record the yield of it. Also to use to the indigo on a cotton and to use the vat dying process.
Safety
To reduce the risk caused by the chemicals I used appropriate PPE (personal protective equipment) which consisted of gloves, goggles and a lab coat. If there are any spillages alert the lab technicians. To stop the inhalation of any of the chemicals conduct the experiment in a fume cupboard.
Apparatus list
- 2-nitrobenzaldehyde
- Acetone
- Glass beakers
- Glass rod
- Sodium hydroxide solution
- Ethanol
- Heat bath
- Buchner funnel
- Filter paper
- Clamp and clamp stand
- Measuring cylinder
- Lab coat
- Safety goggles
- Safety gloves
- Watch glass
- Steam bath
Method for preparing the Indigo
- Firstly, I dissolved 1g of 2-nitrobenzaldehyde in 20cm3 of acetone in a 100cm3 beaker, and diluted the solution with 35cm3 of water.
- Secondly, I stirred the solution vigorously using a glass rod whilst adding 5cm3 of 2 M sodium hydroxide solution.
- Next, I continued to stir for approximately 5 minutes and then I collected the purple-blue precipitate by suction filtration. Suction filtration is a technique for separating a solid product from a solvent or liquid reaction. The mixture of solid and liquid is poured through a filter paper in a Buchner funnel. The solid is trapped by the filter and the liquid is drawn through the funnel into the flask below by a vacuum.
- After that, I washed the product with water until the washings became colourless.
- Thereafter, I washed the product with 25cm3 ethanol.
- Then, I dried the solid with suction for 10 minutes, and then at 100-120 degrees for 30 minutes.
- Finally, I recorded the yield of the product.
Method for Vat dying of cotton
- Firstly, I placed the 100mg of indigo on a watch glass and added a few drops of ethanol.
- Secondly, I made a past by rubbing the mixture with the glass rod.
- Next, I suspended the past in 1cm3 of water in a 100cm3 beaker, and added 3cm3 of 2 M sodium hydroxide solution.
- After that, I made up a solution of the sodium hydrosulphite in 20cm3 of water and added this to the mixture in the beaker.
- Thereafter, I heated up the mixture up to 50 degrees on the steam bath and as soon as a clear yellow solution was obtained I added 40cm3 water.
- Then, I immersed the cotton in the ‘vat’ and left it to dry for 1 hour at 50 degrees. In addition to this I occasionally moved the fabric to ensure even dyeing.
- Finally, I removed the cotton, squeezed it dry and hanged it in the air for 30 minutes to let it develop the colour.
Answers to questions
-
The common name is basic fuchsin. The structure is
- They can be used for food colouring/food dying.
- Azo dyes are a synthetic dye containing the azo group of two nitrogen atoms (NN) connecting aromatic ring compounds. Azo dyes are usually red, brown, or yellow, and make up about half the dyes produced. They are manufactured from aromatic amines. The reaction scheme is below:
Exercise 3 – Synthesis of Acetyl salicylic acid (Aspirin)
Objective/Theory
The aim of this report is to determine the yield and the purity of aspirin that we synthesised from acetic anhydride and salicylic acid. The way in which the purity will be determined is by finding its melting point. The theory is that I will be testing is to find out the purity and the yield of the aspirin that we produce.
C2H603 + C7H603 C9H804 + C2H402
Since we know all the details of what went in and the stoichiometry of the reaction shows that 1mol of salicylic acid will react with 1mol of acetic anhydride which will produce 1 mole of aspirin we can use the data to calculate the theoretical yield that can be obtained and once we have this information we can use that to deduce the percentage yield. The melting point of pure aspirin is in the region of 35-40 c we can use this information to find out the purity of the aspirin.
Safety
The chemicals that i used were potentially dangerous so that’s why i had to take great to reduce the human error. For this experiment i carried out a COSHH assessment and I also brought with me the MSDS sheets for all the chemicals that we were going to use.
Furthermore, to reduce the risk caused by these chemicals i used appropriate PPE (personal protective equipment) which consisted of gloves, goggles and a lab coat. If there are any spillages alert the lab technicians. To stop the inhalation of any of the chemicals conduct the experiment in a fume cupboard.
Apparatus List
- Clamp and Clamp stand
- Isomantel
- Buckner Funnel and Flask
- Capillary Tube
- Bunsen Burner
- Melting Point Apparatus
- Refluxing Apparatus
- Filter paper
- Tripod
- Gauze
- Distilled Water
- Beakers
- Balance
- Spatula
- Glass Rod
- Measuring Cylinder
- Pipette
- 2-hydroxybenzoic acid
Method
- Firstly, I added approximately 3.50g of 2-hydroxybenzoic acid and 8cm3 of acetic anhydride.
- Next, I added 1cm3 of phosphoric acid and swirled the mixture.
- Then, I fitted the flask wit ha reflux condenser and reflux the mixture with an isomantal for 10 minutes.
- After that, without cooling I added 4cm3 of water in small portions down the condenser. This made the unused anhydride hydrolyse and the contents of the flask to boil.
- Thereafter, when the reaction was over, I removed the condenser and poured the mixture into a 250cm3 beaker filled with approximately 100cm3 of cold water.
- Next, I cooled it to room temperature and stirred to induce crystallisation.
- Then, I collected the product by suction filtration and washed it with 5cm3 of ice-cold water.
- After that , I re-crystallised from the water.
- Then, I weighted the total yield.
- Finally, I calculated the % yield and found the melting point of yield.
Results table
Salicylic Acid
Aspirin
The stoichiometry of the reaction shows there is a 1:1 ratio. Therefore we can work out the theoretical yield.
Relevant molecular mass of salicylic acid= 138
Number of moles of salicylic acid = mass/rmm
= 50.1208/138
=0.3632
Relevant molecular mass of aspirin = 180
The mass of aspirin produced = moles x mr
= 180 x 0.3632
= 65.376g
Theoretical yield of aspirin = 65.376g
Actual yield of aspirin = 46.8421g
Therefore % yield = Actual yield/ theoretical yield x 100
= 46.8421/65.376 x 100
= 71.65 %
Conclusion
As you can see from the calculations the ideal reaction did not take place this was due to:
- Not given enough time for the reaction to complete
- It was very hard to regulate the temperature at 70 c with the equipment provided.
- Some residue remained when transferring contents from the flask to the beaker.
- Some of the product was left behind when filtering.
After reviewing the experiment once more I have come to the conclusion that with the apparatus and method that I used I achieved a relatively high yield and purity therefore I am pleased with the way the experiment went.
