Core Practical 15 Lab

Analyse organic and inorganic unknowns

Aims

To research the tests for ions and organic compounds

To successfully test unknown substances to establish their identity

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

Testing Organics

Testing inorganics

Learning Tip

Make sure you know the flame test colours for the ions of Group 1 and Group 2 elements.
Negative test results are important as they inform you what your unknown substance is not.

Things to consider CPAC 2c

CPAC 2c- Identifies and controls significant quantitative variables where applicable, and plans approaches to take account of variables that cannot readily be controlled.

· Choose appropriate equipment for measuring solutions

· Choose appropriate equipment for maintaining temperatures

· Hold test tubes in rack

· Check temperatures with thermometer

· Use blue Bunsen flame during flame tests

· Clean wire rod between flame tests

· Use clean test tubes and pipettes for each test

· Keep lab bench tidy and organised

· Work methodically

· Label test tubes

Things to consider CPAC 4a

CPAC 4a – Makes accurate observations relevant to the experimental or investigative procedure.

· Correctly identify colour changes for organic tests from and to

· Correctly identify colour changes for inorganic tests from and to

· Correctly identify flame test colours.

· Identify other signs of chemical reactions eg fizzing and bubbling / temperature changes

· Recall expected results of different chemical tests

· Understand negative results are important in identifying unknowns

Equipment

● concentrated hydrochloric acid ● 1 mol dm−3 sodium hydroxide ● 1 mol dm−3 nitric acid ● 0.1 mol dm−3 silver nitrate solution ● 1 mol dm−3 ammonia solution ● 1 mol dm−3 dilute hydrochloric acid ● barium chloride solution ● limewater ● bromine water ● sodium carbonate solution ● ethanol ● concentrated sulfuric acid ● four tubs labelled A, B, C and D ● three bottles labelled X, Y and Z ● nichrome wire ● delivery tube ● Bunsen burner and safety mat ● test tubes and bungs ● distilled water ● dropping pipette ● spatula ● boiling tube ● 250 cm3 beaker ● 100 cm3 beaker ● access to a kettle

Procedure

Identifying inorganic ions

1. Look up how to carry out the flame test to identify metal cations.

2. Write a plan for the safe conduct of a flame-test experiment. You should describe in detail how you would carry out the experiment and the results you would expect.

3. Look up how to use sodium hydroxide to identify metal cations.

4. Write a plan for the safe conduct of this sodium hydroxide experiment. You should describe in detail how you would carry out the experiment and the results you would expect.

5. Look up how to use silver nitrate to identify halide ions.

6. Write a plan for the safe conduct of this silver nitrate experiment. You should describe in detail how you would carry out the experiment and the results you would expect.

7. Look up how to test for sulfate ions.

8. Write a plan for the safe conduct of this experiment to test for sulfate ions. You should describe in detail how you would carry out the experiment and the results you would expect.

9. Look up how to test for carbonate ions.

10. Write a plan for the safe conduct of this experiment to test for carbonate ions. You should describe in detail how you would carry out the experiment and the results you would expect.

11. Carry out your experiments to identify substances A–D.

12. Pay particular attention to the management of safety.

Organic analysis

1. Look up how to test for alkenes.

2. Write a plan for the safe conduct of this experiment to test for an alkene. You should describe in detail how you would carry out the experiment and the results you would expect.

3. Look up how to test for an aldehyde.

4. Write a plan for the safe conduct of this experiment to test for an aldehyde. You should describe in detail how you would carry out the experiment and the results you would expect.

5. Look up how to test for carboxylic acids.

6. Write a plan for the safe conduct of this experiment to test for carboxylic acids. You should describe in detail how you would carry out the experiment and the results that you would expect.

7. Carry out your experiments to identify substances X–Z.

8. Take appropriate safety precautions

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 6,10A,15B,40A,47A,67,87,91A,95A,98A,98B,26,19A,55B,45C,83,38A

Wear goggles.
Concentrated hydrochloric acid, sodium hydroxide and concentrated sulfuric acid are corrosive.
Nitric acid, hydrochloric acid and limewater are irritants.
Barium chloride and bromine water are toxic and irritants.
Ethanol is flammable – do not use it near a lit Bunsen burner.
Pay attention to the hazard warnings on the tubs and bottles of unknown substances. In particular, if anything is marked flammable, do not use anywhere near a lit Bunsen burner. If heating a flammable substance is required then it must be heated by standing it in a beaker of hot water.
Perform a risk assessment using up-to-date information before this practical is carried out.
Disposal: All the ammoniacal silver nitrate solution should be washed down the foulwater drain with plenty of water. It must not be stored – silver filaments form, which have been known to explode.

Things to consider CPAC 3b

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

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

· Sets up work space in an organised fashion

· No spillages/deals with spillages appropriately with minimal fuss

· Keeps 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

· Wears safety goggles, gloves & lab coat throughout

Required Resources

Core Parctical 15 - Student Sheet.docx

Home Labs

Core Practicals

Return to Core Practical 15

Consult CLEAPSS Hazcards® 6,10A,15B,40A,47A,67,87,91A,95A,98A,98B,26,19A,55B,45C,83,38A Perform a risk assessment using up-to-date information before this practical is carried out

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