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

Identifying an Unknown Compound

Extracts from this document...

Introduction

Identification of an Unknown Organic Compound Ensure a lab coat, safety glasses and gloves are worn during the experiments and work in a ventilated area. For all experiments test tubes and pipettes will be required. ALKENES: Alkenes contain a double carbon-carbon bond. APPARATUS: Unknown compound, bromine water. METHOD: Add 5 drops of bromine water to a test tube containing 1cm3 of the unknown and shake. OBSERVATION: Bromine water will decolourise from orange. EXPLANATION: The alkene decolourises bromine water and produces 1,2-dibromoethane. The double bond allows electrophilic addition reactions to occur. HAZARDS: Bromine vapour released from the water is 1^harmful^1 (see appendix). ESTERS: Esters are sweet- smelling products from reactions between carboxylic acids and alcohols. APPARATUS: Unknown compound, phenolphthalein, water bath, NaOH. ...read more.

Middle

Phenol- 3^corrosive^3 and 4^toxic^4. CARBOXYLIC ACIDS: Carboxylic acids are products of the oxidation of a primary alcohol or an aldehyde. Their functional group is -COOH. APPARATUS: Unknown compound, water, limewater, NaHCO3. METHOD: 3Add water and NaHCO3 to the unknown compound.3 OBSERVATION: Effervescence occurs after NaHCO3 is added; test the gas with limewater and it will go cloudy. EXPLANATION: Carboxylic acids although weak acids react like any other acid and undergo the same reactions. So CO2 is produced when reacted with NaHCO3. HAZARDS: NaHCO3- 2^irritant^2. CARBONYL COMPOUNDS: Carbonyl compounds consist of the C=O bond, examples are aldehydes, ketones and esters. However the 2,4-DNPH test is only positive for aldehydes and ketones. APPARATUS: Unknown compound, 2,4-DNPH. METHOD: Add 5 drops of 2,4-DNPH to the unknown in a test tube. OBSERVATION: A deep yellow/ orange precipitate appears. EXPLANATION: 4See diagram below. ...read more.

Conclusion

The orange dichromate (VI) ion, Cr2O72-, is reduced to green chromium (III), Cr3+. If the solution has remained orange it proves the presence of a tertiary alcohol as they cannot be oxidised.6 Another test can be carried out to confirm the presence of a tertiary alcohol, it is known as Lucas' test. APPARATUS: Lucas' reagent: a solution of ZnCl2 in concn HCl. METHOD: Add 2cm3 of Lucas' reagent to 1cm3 of the unknown and shake. OBSERVATION: A cloudy emulsion may be seen rapidly or no reaction may occur after 5 minutes. EXPLANATION: 7The reagent dissolves the alcohol and removes the OH group leaving a carbocation. The cloudiness is caused as the carbocation reacts with Cl- forming a chloroalkane. Tertiary alcohol is present if the emulsion forms rapidly and a primary alcohol if no reaction occurs.7 HAZARDS: K2Cr2O7- 4^toxic^4 and 6^oxidising^6. H2SO4- 1^harmful^1 and 3^corrosive^3. Lucas' reagent- 4^toxic^4 and 3^corrosive^3. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Organic 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 AS and A Level Organic Chemistry essays

  1. Marked by a teacher

    Reactions of aldehydes and ketones. The purpose of this experiment is to compare ...

    5 star(s)

    The solution was dark blue after the precipitate redissovled. 16. For ethanal, the solution turned dark green and after a long period of time, there was brown solid deposited at the bottom. 17. For propanone, there was no observable change.

  2. Determination of the formula of Hydrated Iron (II) Sulphate crystals

    In order to improve the accuracy of the results; rather than only completing 3 repeats, 12 repeats should be completed and an average titre found between the 12. This would greatly increase the reliability as well as accuracy of the experiment .

  1. Find the enthalpy change of combustion of a number of alcohol's' so that you ...

    Also use a calorimeter that conducts heat more efficiently. Another major error I my experiment is incomplete combustion of the fuel. It produces soot and CO, therefore resulting in the release less energy to the water and therefore decreasing the enthalpy of combustion value.

  2. The aim of this experiment is to produce Aspirin. This is an estrification in ...

    This suggests that the re-crystallised aspirin is pre with very little impurities. However if impurities are present, forward titration will neutralise acetylsalicylic acid and the impurities as well. Also using this titration it was difficult to identify the end point because aspirin is a weak acid and the reaction takes place very slowly.

  1. investigating the amount of ascorbic acid present in fruit

    of Average Results: Appendix D shows a bar chart of my average titres for the orange, lime and lemon sample I used in the experiment. The x-axis indicates the sample of fruit that was used in the titration and the y-axis shows the average titre which is measures in cm3.

  2. Comprehensive and Detailed Chemistry notes

    atoms split into separate oxygen atoms, the atoms are called oxygen free radicals. -- These have 2 paired electrons and 2 unpaired -- This makes radicals very reactive -- Oxygen free radicals are more reactive than ozone * identify the origins of chlorofluorocarbons (CFCs)

  1. Compare the enthalpy changes of combustion of different alcohols

    It is important that neither is inhaled or swallowed. If any of these two fuels were to spill, I would inform the nearest member of staff rather than clean it up myself. The member of staff would instruct me what to do. Whilst doing the experiment, it would be necessary to carry it out in a fume cupboard so that no fumes get into the atmosphere.

  2. Investigating the Enthalpy Changes of Combustion of Alcohols.

    = 966.94 J x 46/1.95 ?E = 22573.98 J ?E = 22.6 kJ (or -22.6 kJ) Now, we know that the total energy released to the water and the copper calorimeter is -456.5 kJmol-1, however this is still nowhere near the actual amount of energy released when ethanol is burnt, -1367.3 kJmol-1.

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