• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Identification of an Organic Unknown.

Extracts from this document...

Introduction

A-Level Chemistry Coursework Practical 1- Identification of an Organic Unknown Introduction 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: (1.TEST WITH UNIVERSAL INDICATOR) TURNS RED TURNS ANY OTHER COLOUR (2.TEST WITH BROMINE WATER) (3.TEST WITH 2, 4 DNP) (4.TEST WITH TOLLENS REAGENT) 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. 1. Test with Universal Indicator EQUIPMENT: Universal indicator Test tube Pipette 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. ...read more.

Middle

4. Test with Tollens Reagent EQUIPMENT: Test tube Pipette Silver nitrate solution Sodium hydroxide solution Ammonia solution Water Bath PROCEDURES: Put about 1cm� of 0.05M silver nitrate solution into a very clean test tube and add 3 or 4 drops of sodium hydroxide solution. Drop by drop; add ammonia solution until the precipitate of silver oxide nearly dissolves. Add a few drops of unknown to the tube and shake gently. Place tube in a beaker of warm water, note observations and immediately rinse out test tube. OUTCOMES: A change from clear to a silver mirror precipitate on the side of the test tube indicates the presence of an aldehyde. No change indicates a ketone. EXPLANATION: Aldehydes are easily oxidised to make them acids. Ketones cannot be oxidised, as there is no place for the oxygen from the oxidising agent. When the silver nitrate is mixed with ammonia to form Tollens reagent, the complex ion [Ag (NH3) 2] + is formed. This is reduced to silver during the process; Tollens reagent is the oxidising agent. SAFETY: Follow general safety procedures and silver nitrate solution, sodium hydroxide solution and ammonia solution are all corrosive so always make reference to the relevant hazcards. 5. Test with Acidified Potassium Dichromate EQUIPMENT: Test tube Pipette Potassium dichromate solution Sulphuric acid Water bath PROCEDURES: Add 1cm� of potassium dichromate ...read more.

Conclusion

To get a more specific answer I had to use the physical techniques as well. With all chemical techniques there is always a possibility of an error occurring through the contamination of equipment, chemicals or the unknown compound itself. This would result in an incorrect result so therefore I had to pay particular care when conducting all parts of the chemical tests. None of the spectra are particularly useful independently and only really come in to good use when one or more of them are used together. The mass spectrum gives the relative atomic mass of the unknown this can be used to give a general idea of the molecular formula. However the atomic mass could be appropriate to more than one functional group so I would not be able to use this technique on its own to find the identity of any organic unknown substance. The infrared spectrum doesn't simply make a distinction between an aldehyde and ketone so other tests would be required to make this distinction if this situation occurred. The NMR spectrum was very useful as it gave most information needed to identify an unknown. Another technique I could use to identify an unknown which I didn't use would be finding the melting and boiling points. There would however be difficulties if the compound contained any impurities so I would have to make sure the organic unknown was pure. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Aqueous Chemistry section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Here's what a star student thought of this essay

4 star(s)

Response to the question

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 ...

Read full review

Response to the question

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.

Level of analysis

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.

Quality of writing

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


Did you find this review helpful? Join our team of reviewers and help other students learn

Reviewed by alireza.parpaei 14/03/2012

Read less
Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Aqueous Chemistry essays

  1. Marked by a teacher

    The Effect of pH on the Strength of Keratin (hair protein).

    4 star(s)

    ions will cause ionisation of the important bonds holding the keratin fibres together. This will cause damage to the bonds in the hair strand leaving it with less resilience and less strength. Method: To test my prediction I shall immerse individual hair strands in solutions of five (varying)

  2. Indigestion Tablets Investigation

    This is the same as what I predicted (see 'Justification' for theory). Not including the 350C line, the lowest temperature experiment lasted the longest time (24oC, for 6mins), decreasing in time until the highest temperature (72oC, for 1min 45secs).

  1. Investigating the effects of varying pH levels on the germination of cress seeds

    be detrimental to the experiment as a whole, as all of the samples will be subject to identical conditions, whatever the change. After completing the experiment, it was clear that the only samples which were successful in any germination were those of both acids with either 0% concentration or 20% concentration i.e.

  2. The aim of this experiment is to answer the following question: What is the ...

    Fill the water bath up with water, and set water bath to the desired temperature. In the case of my preliminary work I will set it to 20oC and 60oC. I will place a thermometer in the bath to make sure the correct temperature is reached.

  1. Preparation of Potassium Trioxalatoferrate (III)

    Once dry, the crystals and clock glass were reweighed. Safety Safety glasses were worn throughout this experiment. Gloves were also worn throughout the experiment. Results Mass of beaker = 48.69g Mass of beaker + hydrated ammonium iron (II) sulphate = 53.64g Mass of hydrated ammonium iron (II) sulphate = 4.95g hydrated ammonium iron (II)

  2. Why do penguins huddle to keep warm?

    70 degrees and measure the temperature of it until it is at 70 degrees and then submerge the test tube arrangement into it until they are all fill. By doing this I shall have assured that all the test tubes start off at 70 degrees unlike if I were to pour water into each individual test tube.

  1. The oxidation of Ethanol.

    The next step involved mixing of the sodium dichromate, which was a bright orange solid, and the water with the ethanol, which was a clear solution. The reason for this was because the reaction between the two solutions caused it to continue boiling.

  2. Precipitation of Salts & Identification of Unknown Solutions

    light yellow solution -No precipitate Bubbly, fizzy, dark orange solution -Thick orange precipitates formed at the bottom Clear, light yellow solution -No precipitate Clear solution -No precipitate Mg2+ Clear solution -No precipitate Thick, white cloudy precipitates floating around the tube Clear solution -No precipitate Cloudy, misty, white precipitates on top

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work