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

Identify an unknown organic compound.

Extracts from this document...


IDENTIFICATION OF AN ORGANIC UNKNOWN Introduction: In this assessed practical we have to plan a sequence of simple chemical test tube tests in order to identify an unknown organic compound containing a functional group. The functional group could be an alkene, primary alcohol, tertiary alcohol, aldehyde, ketone, carboxylic acid, ester or phenol. Safety: During all experiments Laboratory coats and safety glasses must be worn. When using a Bunsen burner tie long hair back and use a safety mat to protect the bench. Plastic gloves must be worn when handling the chemicals. There are some chemicals that need special attention when handling them: * 2, 4-DNP - is an irritant to skin and eyes. * Bromine water - is harmful if ingested or inhaled and prolonged skin contact can cause burns. It is an irritant to the eye and also make sure there is good ventilation. * Silver nitrate - is an irritant and can cause burns. * Ammonia - is an irritant and can cause burns. * Sodium hydroxide - is an irritant to skin and eyes. * Iron (III) Chloride - is toxic and can cause burns. Can also give off Hydrogen Chloride gas. * Sodium carbonate - is a low hazard, but still needs to be considered * Organic unknown - can be considered to be toxic and harmful if swallowed. If any of the above chemicals come into contact with skin or eyes, wash off immediately with cold water. ...read more.


A positive test will give a violet colour. Test 3 - 2,4-DNP Using a dropping pipette, place 5 drops of the organic unknown in a test tube. Measure out and add 2cm3 of 2,4-DNP solution. This is if the unknown is a liquid. If the unknown is a solid then measure out 20cm3 of de-ionised water and add 1g of the unknown solid and 2cm3 of 2,4-DNP in a test tube. Now do the same for the unknown if it is a liquid. Give the test tube a mix. A positive test will give an orange/yellow precipitate and a negative test will not give a precipitate. Test 4 - Tollens reagent (Ammoniacal Silver Nitrate solution) Take a 500cm3 beaker and fill it approximately half full with water. Place this on a tripod and gauze and heat the beaker of water using a Bunsen burner. Measure out 1cm3 of 0.05 mol dm-3 of silver nitrate in a measuring cylinder and place it in a test tube. Now add 5 drops of sodium hydroxide solution (2M) using a dropping pipette. Using a different dropping pipette, add 2M of ammonia solution drop wise until the precipitate has just dissolved. Then add 5 drops of the organic unknown and shake gently. Place the test tube in the beaker of warm water. A positive test will give a silver mirror on the inside of the test tube and a negative test will not give a mirror. ...read more.


Place this on a tripod and gauze and heat the beaker of water using a Bunsen burner. After the water has boiled, remove the flame and place the test tube into the beaker. Leave the test tube for about 5 - 10 minutes. A positive test will give a green coloured solution and a negative test will not give a green colour. Potassium Dichromate is a reagent, which oxidises alcohols when mixed with dilute sulphuric acid and warmed. The dichromate ion gives a colour change from orange to green, because it is reduced from an oxidation state of +6 to +3. However, this test does not oxidise a tertiary alcohol, therefore does not turn green. Alternative tests: For some of the tests that have been selected, there are alternatives that can be used. Firstly, to distinguish an aldehyde and a ketone, a test involving a solution called Fehling's can be used. This would involve mixing Fehling's A (aqueous copper sulphate), with Fehling's B (aqueous sodium hydroxide) and then adding the carbonyl. This test would give a brick red precipitate with an aldehyde but no precipitate with a ketone. However, Tollens will be used because it a test which is more familiar to me. An alternative test for an alkene that could be used is to add iodine in methylene chloride solution. This will produce a light tan solid, while retaining the purple colour of the iodine solution. However, this will not be used as it also gives a positive test for some alcohols and ketones. ...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

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. Peer reviewed

    Identification of an Organic Unknown.

    4 star(s)

    SAFETY: Follow general safety procedures and bromine water can be toxic and corrosive so always make reference to the hazcards. 3. Test with 2, 4 DNP (2, 4-dinitrophenylhrazine) EQUIPMENT: Test tube Pipettes 2, 4 DNPH solution 1cm� of Ethanol Water Bath PROCEDURES: To 1cm� of 2, 4-dinitrophenylhydrazine solution and 1cm�

  2. Identification of an Organic Unknown.

    HCOO-Na+ + H20 + CO2 Esters also contain a C=O bond but here the carbon is attached to another oxygen, which is bonded with another carbon. There is no simple test to carry out for identifying an ester, however esters have a distinct fruity smell.

  1. identifying an unknown compound

    Test to find an alcohol Procedure- Add 1cm3 of potassium dichromate into a test tube also add 1 cm of sulphuric acid to the test tube and add few drops of the unknown and warm using water bath. Outcome- A colour change to green shows an alcohol is present.

  2. Organic compound identification.

    proved that there was an OH group of an alcohol in the compound. 3. The color changing of the solution from pale yellowish/green to pale blue tells us that the alcohol has been oxidized to ketone. Identity And Structure The unknown compound A is likely to be Propan-2-ol.

  1. Identification of an unknown organic compound

    Primary alcohols are oxidized on heating with acidified aqueous potassium dichromate: however tertiary alcohols remain unchanged with the reagent. (Chemistry 1 endorsed by OCR page 131 first paragraph). The test I will be using to identify whether it is a primary or tertiary alcohol will be by adding acidified potassium dichromate to the unknown organic compound.

  2. How much Iron (II) in 100 grams of Spinach Oleracea?

    This could have effected the results of this experiment as it was focusing on the effect temperature has on this particular redox reaction. Improvements This experiment could be improved in a number of ways. The Oxalic Acid (aq) and the Potassium Manganate (VII)

  1. Identification of an organic unknown.

    Phenol - or hydroxybenzene Iron (III) chloride when reacted with phenol will produce a violet/purple colour (in fact, any colour other than yellow indicates a type of phenol is present.) Method - logically explained: Firstly I will need to gather groups that have the same reacting atoms.

  2. To identify an organic unknown using basic cohesive chemical tests to discover the functional ...

    Phenol acts as a very weak acid which will neutralise a strong base. By adding sodium hydroxide to the Phenol Sodium Phenoxide is made along with water. Then if concentrated HCl is added a milky emulsion is formed indicating the presence of Phenol.

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