1. Chemical synthesis Lesson 5

2. Learning objective: To understand how the purity of a sample can be determined by performing a titration. Must: Give examples of products with different grades of purity. Should: Be able to carry out a titration. Could: Measure accurately the purity of the sample of citric acid. Keywords: Pure, grades, titration, burette and end point. Starter: What does pure mean?

3. Pure. Only contains one substance. Free from contaminants. Is the water opposite really pure?

4. Both are salt are they the same purity? Rock saltTable salt

5. Grades of purity. Purifying a chemical is done in stages. The higher the purity the more expensive it becomes. Manufacturers only buy the quality most suitable for their purpose. Both contain limestone, which will be most pure?

6. Deciding the grade of chemical. 1. The amount of impurities. 2. What the impurities are. 3. How they can affect the process. 4. Whether they will end up in the product, and whether it matters if they do.

7. Checking purity. There are various methods of checking purity; 1. Melting points. 2. Spectroscopic techniques. 3. Chromatography. 4. Titration.

8. Discover - Performing a titration. Key skills Read and understand texts and take appropriate action. Use appropriate mathematical procedures. Team worker – collaborate with others to work towards common goals.

9. Titration Step 1. Fill the burette with a solution of acid or alkali of known concentration.

10. Titration Step 2. Weigh out accurately the sample that you want to test the purity.

11. Titration Step 3 Dissolve the substance in pure water. Add a few drops of indicator.

12. Titration Step 4. Add alkali/acid from the burette to the solution. Swirl the contents during each addition. Near the end point (when the indicator changes colour) add the alkali/acid drop by drop.