RP 6 - Organic Tests

Question 1

How do you test for an alcohol?

Answer 1

1. Add 1 cm^3 of alcohol to a test tube, add a small piece of sodium
2. Presence of alcohol is indicated by a white precipitate and effervescence

Question 2

How do you distinguish between different alcohol types? (primary, secondary etc.)

Answer 2

1. Heat under reflux with acidified potassium dichromate (VI).
2. Primary and secondary alcohols will be oxidised - shown by a colour change from orange to green. Tertiary alcohols can’t be oxidised and will remain orange

Question 3

How do you test for an aldehyde?

Answer 3

• Add Fehling’s solution to the sample
• If an aldehyde is present, a red precipitate will form

Question 4

How do you test for an alkene?

Answer 4

• Add bromine water to the sample
• If an alkene is present, the bromine water will decolourise

Question 5

How do you test for a carboxylic acid?

Answer 5

• Add Na2CO3 to the sample
• If a carboxylic acid is present, CO2 will be given off

Question 6

How do you test for a haloalkane?

Answer 6

1. Add 5 drops of haloalkane to about 1 cm^3 of NaOH solution in a test tube
2. Warm the contents of the test tube at 60°C for a few minutes
3. Add 2 cm^3 of nitric acid and 1 cm^3 of silver nitrate solution
4. If a haloalkane is present, a precipitate should form. The colour of the precipitate formed depends on the halide ion present in solution
   - White = Cl-, Cream = Br- and Yellow = I-

Question 7

What are some common potential hazards, risks and controls in the lab when doing organic tests?

Answer 7

• Bunsen burner risks burns so keep away from flammable chemicals and away from the edge of the desk
• Chemicals may be: an irritant or corrosive, causing irritation to skin, eyes or lungs; toxic; flammable. So handle with care and while wearing gloves. Also, keep away from the edge of the desk & from an open flame and don’t ingest
• Glassware i.e. beakers or test tubes may break or cut you so handle with care and keep away from the edge of the desk