Required Practical 6 - Testing for functional groups

Give 2 ways for testing for an alcohol

1. Using Metallic sodium

2. Using Potassium Dichromate

Give the 3 step method to test for alcohols via Metallic sodium

1. Add a small piece of metallic sodium to the solution

2. Place test tube above the reaction to collect Hydrogen (or use a water-gas jar)

3. Dispose any excess sodium safely using excess ethanol in a separate beaker

Give the 1 step method to test for alcohols via Potassium Dichromate (+pos/neg results)

1. Add potassium dichromate to solution

• Positive = Orange → Green

• Negative = Orange

Give the 4 step method to test for aldehydes

1. Add Fehlings to all test tube solutions

2. Add 5 drops of Fehlings to 1cm³ Sodium carbonate in a test tube containing a few anti-bumping granules and add 1cm³ of the solution

3. Warm the test tube gently for approx 2 minutes in a hot water bath

4. Observe changes

What is the positive test result for aldehyde testing?

Blue → Red

Give the 3 step method for testing for Alkenes (+ positive result)

1. Add bromine water to a few drops of alkene

2. Shake the contents of the tube vigorously 

3. Observe colour change

• Orange → Colourless

Give the 2 step method to test for Carboxylic acids (+positive result)

1. Place a spatula of solid Sodium carbonate in a test tube and add a volume dilute ethanoic acid using a pipette

2. Collect the gas and bubble to limewater

• Limewater turns cloudy

Give the 3 step method to test for Halogenoalkanes (+ positive result)

1. Using a pipette add 5 drops of the sample to a volume of NaOH in a test tube

2. Warm contents of the test tube for a few minutes in a beaker with hot water (60 degrees celsius)

3. Acidify contents of the test tube by adding dilute nitric acid and then add some silver nitrate

• Silver halide forms → Precipitate forms

Give 3 ways to uncertainty for experiments

1. Compare to known solutions

2. White tile under containers to observe colours

3. Using separate, dry/clean test tubes