Identification of an Organic Unknown.

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A-Level Chemistry Coursework

Practical 1- Identification of an Organic Unknown


In this investigation I will be supplied with a compound which will contain one of the following functional groups:

* Alcohol

* Aldehyde

* Carboxylic acid

* Ester

* Ketone

* Phenol

The following is a flow diagram of the chemical tests I will use to identify the functional groups outlined above:






General Safety Procedures

For all experiments involving any unknown compound the wearing of goggles, lab coat and gloves is necessary because one or more of the compounds could be an irritant/corrosive/etc.

. Test with Universal Indicator

EQUIPMENT: Universal indicator

Test tube


PROCEDURE: Add several drops of the unknown substance to universal indicator inside a test tube using a pipette.

OUTCOME: A colour change to red indicates either a carboxylic acid or phenol is present. Any other colour change shows alcohol, aldehyde, ketone or ester.

EXPLANATION: Single indicators, such as litmus, are very weak acids. If the concentration of hydrogen ions is changed at a certain pH the indicator will change to a different structure.

Universal indicator is a mixed indicator i.e. it is several indicators with different pH values mixed together. When added to solutions of different pH, different indicators change colour as above. The colour you see is a result of colour mixing. The colour has been linked to a specific pH and a colour chart provided.
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SAFETY: Follow general safety procedures and be aware that universal indicator can be dangerous so always make reference to the hazcards.

2. Test with Bromine Water

EQUIPMENT: Test tube


Bromine water

PROCEDURE: Add several drops of bromine water into a test tube which if filled with 1cm³ of the unknown substance.

OUTCOME: A white precipitate formed indicates a phenol present; no change shows a carboxylic acid.

EXPLANATION: Aqueous phenol decolourises bromine water to form a white precipitate of 2, 4, 6-tribromophenol.

The presence in phenol of the OH ...

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The grammar, spelling and the usage of technical terms are completely fine and there is nothing to be pointed out.

The analysis of the experiment is good and produces a very detailed manual for the reader. However there can be some debate concerning some stages of the test. The usage of Universal indicator might not be accurate as the pH of phenol is above 5 and very close to 6 which is not easily detected by Universal indicator so usage of a digital pH meter or blue litmus paper would be a better option. I can also point out at the test used to distinguish between an alcohol and an ester. This test definitely works unless a tertiary alcohol is used as stated however we do not know if the alcohol is tertiary or not. so it is better to use Phosphorus pentachloride (PCl5) to detect alcohols as all alcohols produced steamy fumes of Hydrogen Chloride with PCl5. In another part of the coursework, If Brady's reagent test is negative it would only conclude that alcohol or ester is the compound since the posiblity of Phenol & Carboxylic acid is already eliminated before doing the test with the Brady's reagent. However in general this is a very excellent coursework.

An excellent coursework that produces a very detailed series of tests for identification of organic compounds. This is an A Level coursework however it is classified under GCSE. This coursework might be extremely confusing for the GCSE level chemistry. The coursework is very clear and easy and well-organised to give the reader a very complete information about this procedure. The usage of diagram/chart to show the series of the reactions is incredible however for this level of coursework, diagrams for the apparatus used for each test should be included.