Safety:
I aim to carry out the experiment in accordance with safety regulations and procedures in an orderly and coherent manner that will allow me to obtain accurate and reliable results.
When conducting my experiment in the laboratory, certain precautions need to be taken. Safety of the user and others safety are paramount. The following precautions will be taken into consideration:
- When handling the phenylammonium chloride, I will take great care not to spill any of it on myself or others as the substance is carcinogenic.
- Due to Ethanoic anhydride’s odour, the preparation will be done in a fume cupboard
- I will wear a lab coat at all times as to prevent any damage to my body from accidental spillages
- At all times, I will be wearing safety goggles as to prevent any acid or foreign bodies entering my eyes.
Calculations:
Organic reactions typically produce a lower yield than expected from the balances equation. This yield is usually expressed as a percentage yield.
The formula I will use is:
Actual Yield
Percentage yield = 100%
Theoretical Yield
Apparatus:
The apparatus I will need to conduct this experiment is as follows:
-
Lab coat 2cm3 Ethanoic Anhydride
- Gloves Buchner’s Funnel
- Glass rod spatula
- Beaker Bunsen burner
- Hot water Heat proof mat
-
50cm3 Measuring cylinder capillary tube
- 1.0g of phenylammonium chloride weighing boat
- Water Glass weighing scale
- Conical flask ( 2) Glass funnel
- Sodium Ethanoate 6.0g Rubber bung
- Filter paper
Diagram : Diagram showing the set up of apparatus:
Method:
- Dissolve 1.0g of phenylammonium chloride in 30cm3 of water in a conical flask
- Prepare a solution of 6.0g of sodium ethanoate in 25cm3 of water in a conical flask
- Carefully add 2cm3 of Ethanoic anhydride to the solution of phenylammonium chloride and stir vigorously until all of the Ethanoic anhydride has dissolved. Now add the sodium ethanoate solution and continue to stir for a further three minutes.
- The solid that has collected is a crude sample of the antifebrin. This should be collected by filtering under reduced pressure. It should then be washed with a little cold water.
- Recrystallise the whole of your product from the minimum volume of hot water. Allow the mixture to cool and when crystallisation is complete, filter off the pure product under the reduced pressure.
- Dry the bulk of your product in air and a small portion between the filter paper. Use this small portion to determine the melting point of the sample.
The reaction that occurs is of the following:
C6H5NH3+CL- + (CH3CO)2O CH3CONHC6H5 + CH3COOH + HCL
Analysing Evidence and Calculations:
Using a portion of the sample produced, I placed this portion into a capillary tube and use a device to measure the melting point of the substance which I found to be at 109.5oC
Therefore using the above mass of the purified sample the percentage yield can be calculated as follows:
Actual Yield
Percentage yield = 100%
Theoretical Yield
The reaction that occurs is of the following:
C6H5NH3+CL- + (CH3CO)2O CH3CONHC6H5 + CH3COOH + HCL
Molar ratio:
1 : 1
The molar mass of Phenylammonium chloride (C6H5NH3CL) is: 129.5 g mol-1
The amount of Phenylammonium chloride used 1.0g
Therefore the moles of Phenylammonium chloride is calculated using:
Mass = 1__ = 0.00722 mol-1
Molar mass 129.5
1 mol of Phenylammonium chloride gives 1 mol of antifebrin.
The molar mass of antifebrin (CH3CONHC6H5) is: 134 g mol-1
Therefore the Theoretical yield of antifebrin is 0.00722 mol x 134 mol-1 = 1.0347g
Actual yield = 0.700 g
Therefore percentage yield: 0.700g x 100 = 67.7%
1.0347
Evaluating Evidence & Procedures:
My experiment worked well and produced good results.
I believe the experimental procedure I followed was coherent and well organized and therefore allowed me to obtain accurate and reliable results, however there is always room for improvement.
There were no anomalous results produced.
To ensure reliability and accuracy of data, I could have used electronic equipment to accurately measure observations. However I could only use the equipment available to me in my school laboratory, therefore I was limited to manual technique whereby some anomalies could occur due to human error.
The precision of collecting data could be improved by:
- Repeating the experiment under laboratory controlled conditions and in an air tight environment
- Repeating the experiment as many times as possible to gain the best possible yield without loosing too much of the product
A perfect reaction would convert all of the starting material to the desired product, but very few do.
My reaction only gave me a yield of 67.7%, reasons why this occurred could be as follows:
- There may have been some side reactions producing by products instead of the desired chemical
- Some of the product is lost during transfer of the reaction mixture from one piece of equipment to another, when the product is purified and separated.
- There may be impurities in the product
- Recovery of all the product from the reaction mixture is usually impossible
Improving any experiment is ultimately reducing any errors within the method.
The experiment could be repeated as many times as possible to gain an average set of results.
