Core Practical 5 Lab

Investigate the oxidation of ethanol

Aim

To oxidise ethanol and use heating under reflux and distillation as practical techniques

These videos & activities will support your laboratory work and help you with the analysis of your results

Techniques

RSC Heating Under Refulx

RSC Distillation

Oxidation of Ethanol

Things to consider CPAC 1a

CPAC 1a - Correctly follows instructions to carry out the experimental techniques or procedures

· Prepare apparatus for reflux:

1. Set up apparatus with minimum help ensuring seals

2. Water in and out correctly set up

3. Ethanol added slowly down condenser with flask on ice

· Carry out reflux:

1. Control heat to flask

2. Water flowing

3. Ensure gases don’t escape

· Prepare apparatus for distillation:

1. Set up apparatus with minimum help ensuring seals

2. Water in and out correctly set up

3. Thermometer in correct place

4. Collection flask

· Carries out distillation:

1. Control heat to flask

2. Water flowing

Chemical Tests

Things to consider CPAC 2a

CPAC 2a - Correctly uses appropriate instrumentation, apparatus and materials to carry out investigative activities, experimental techniques and procedures with minimal assistance or prompting.

· Chose an appropriate place to work – near gas tap & sink

· Set up HUR apparatus confidently with little teacher input

· Confidently rearrange glassware from HUR to distillation

· Carry out the chemical tests on the products confidently, applying good knowledge of the expected positive results

Things to consider CPAC 2b

CPAC 2b- Carries out techniques or procedures methodically, in sequence and in combination, identifying practical issues and making adjustments when necessary.

· Use appropriate sized measuring cylinders to measure out liquids (fresh cylinder for each liquid)

· Water into reflux condenser at bottom, out at top

· Add anti-bumping granules

· Use gas tap to control refluxing rate

· Bulb of thermometer sits at junction of still head

· Collect distillation product over an appropriate (researched) temperature range

· Collect sufficient product to carry out the chemical tests (or changes the volumes accordingly to account for the tests – 4cm³ product minimum needed)

Equipment

chemical-resistant gloves ● 20 cm3 acidified sodium dichromate solution ● anti-bumping granules ● two 50 ml pear-shaped (or round-bottomed) Quickfit® flasks ● Quickfit® condenser ● ethanol ● dropping pipette ● two 10 ml measuring cylinders ● bench acidified potassium dichromate (labelled acidified potassium dichromate for analysis) ● apparatus for distillation with thermometer going up to at least 110 °C ● calcium carbonate powder ● spatula ● magnesium ribbon ● beakers ● 4 test tubes ● universal indicator paper ● Fehling’s solution ● Bunsen burner ● ice-water bath

Procedure

1. Carefully add 20 cm3 of acidified sodium dichromate solution to a 50 ml pear-shaped flask. Cool the flask in an ice-water bath.

2. Set the flask up for reflux (see fig A) keeping it in the ice-water bath.

3. Place a few anti-bumping granules into the pear-shaped flask.

4. Measure out 1 cm3 of ethanol.

5. Using a pipette, add the ethanol a few drops at a time down the reflux condenser. This must be done slowly. Allow for the reaction to subside after each addition before adding more.

6. When all of the ethanol has been added, remove the ice-water bath and allow to warm to room temperature (approximately 5 minutes).

7. Position the flask in a hot water bath using water from a kettle. Light a Bunsen burner and maintain a boiling water bath for 20 minutes. Allow the apparatus to cool.

8. Distil your product using the apparatus shown (see fig B). Collect 3-4cm3 of clear, colourless liquid.

9. Split the distillate into four portions and perform the following tests on each portion:

● Measure the pH of the distillate using universal indicator paper.

● Add a few drops of acidified potassium dichromate solution to 1 cm3 of the distillate. Warm the mixture in a 60 °C water bath.

● Add a quarter of a spatula of calcium carbonate powder to 1 cm3 of the distillate.

● Add a 1 cm long length of magnesium ribbon to 1 cm3 of the distillate.

● Add 1 cm3 of Fehling's solution to 1 cm3 of the distillate. Warm the mixture gently using a water bath.

Understanding How to Stay Safe

Hazcards COSHH

Read the Hazcards COSHH information for the chemicals used in the practical so that you are aware of how to keep yourself and others safe 78C, 98A,40A,19B,59A

Wear goggles.
Ethanol is flammable.
Acidified sodium dichromate is an oxidising agent. It is both corrosive and a carcinogen – wear chemicalresistant gloves

Things to consider CPAC 3b

CPAC 3b - Uses appropriate safety equipment and approaches to minimise risks with minimal prompting.

· Collect all eqpt at start to minimise walking around the lab once practical work

· Set up work space in an organised, tidy & safe fashion

· No spillages/deals with spillages appropriately with minimal fuss

· Keep stoppers on bottles when not in use

· Discuss medical issues prior to practical work that may need considering (ie asthmatic/ epileptic…)

· Correct disposal of reaction mixture (reagents & products) at end of practical

· Area cleared away properly & cleaned down (if needed) for following students without prompting

· Control heat to condenser to avoid gases escaping

· Use of water bath to heat pear shaped flask

· Clamps HUR glassware at neck of pear shaped flask

· Clamp distillation apparatus at neck of pear shaped flask and receiver adaptor

· Wear safety goggles, gloves & lab coat throughout

Required Resources

AS-and-A-level-Chemistry-Core-Practical-5- Student Worksheets.docx

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Consult CLEAPSS Hazcards® 78C, 98A,40A,19B,59A. Perform a risk assessment using up-to-date information before this practical is carried ou

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