1. Titrations How can use titrations to work out the concentration of a chemical Starter: HCl + NaOH  NaCl +H 2 O H + + OH -  H 2 O 1)What do these reactions show? 2)What conditions are necessary for this to occur?

2. explain the importance of checking the purity of chemicals used in synthesis carry out an acid–alkali titration interpret the results of a titration

3. Glossary Titration – a method for measuring the volumes of two solutions that react together. Alkali – A soluble base with a pH more than 7.

4. Titrations -strong acid + strong alkali = neutralise & form a salt -But ONLY if they are in exactly the right quantities. Otherwise, one (acid or alkali) will be in excess Quick Check: -If there is more acid than alkali to start with in a neutralisation reaction, what will happen? The final solution will be acidic

5. Glossary Titration A way to measure volumes precisely End Point The point at which the acid and alkali have reacted completely. This is shown using an indicator.

6. Concentration = no. of moles volume Learn this formula triangle! n cv number of moles concentration (in mol dm -3 ) volume (in dm 3 )

7. The Method V:\Science\Teaching resource store\Freezeray Chem Simulations\titrations[1].swfhttp://www.mhh e.com/physsci/chemistry/animations/chang_7 e_esp/crm3s5_5.swf

8. Calculations Follow the example. Read the instructions and use them to answer the first half of the worksheet.

9. Steps 1) write out balanced equation 2) work out the mole ratio between acid and alkali 3) Write down all the values you know. 4) Use the mole ratio to work out the value of N for the unknown solution. 5) Use the triangle to work out the other values. VERY IMPORTANT – convert all cm3 into dm 3 ( divide by 1000)

10. Titrations 2 How can I work out volumes of substances that are not in a 1:1 ratio? Write a balanced symbol equation for the reaction between sodium hydroxide (NaOH)and sulfuric acid (H2SO4)

11. Non 1: 1 ratios 25 cm 3 of NaOH was reacted with 20 cm 3 of 0.5 mol dm -3 H 2 SO 4. What concentration of NaOH was used? see what you can do!

12. Steps 1) write out balanced equation 2) work out the mole ratio between acid and alkali 3) Write down all the values you know. 4) Use the mole ratio to work out the value of N for the unknown solution. 5) Use the triangle to work out the other values. VERY IMPORTANT – convert all cm3 into dm 3 ( divide by 1000)

13. 2) Working out masses of chemicals in solution.

14. Working out masses using titration In 1 dm3 of a solution there is 1 mole of that solution. We can work out the mass a mole by working out the Mr. e.g. K 2 SO 4 has an Mr of what? K =39 S = 32 O = 16

15. Mr K 2 SO 4 = 174 SO in 1 dm 3 (1 litre) of a solution of K 2 SO 4 there is 174g of K 2 SO 4. in 1 cm 3 there is 174/1000 = 0.174 We can then use this to work out the mass of any amount of solution. E.g. 5cm 3 = 0.174X5 250 cm 3 = 0.174 x 250 600 cm 3 = ?

16. Work out the following 1) What mass of sodium hydroxide is there in a 250cm 3? 3) What mass of copper sulfate is there in a 400cm 3? 4) What mass of sodium carbonate is there in a 820cm 3?