Salt preparation by titration


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Salt preparation by titration method

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Salt preparation by titration

  1. 1. Salts Preparation Preparation of Salts By Titration LEARNER’s OUTCOMES  Describe the process of titration to prepare salts  Write chemical equations for reactions used in the preparation of salts 1
  2. 2. Salts Preparation – Recap Precipitation Method Starting materials: 2 aqueous solutions Products: Insoluble salt and Soluble salt Eg: How do you prepare barium sulfate salt? barium nitrate + sodium sulfate  barium sulfate + sodium nitrate Ba(NO3)2 (aq) + Na2SO4 (aq)  BaSO4 (s) + 2NaNO3 (aq) 2
  3. 3. Salts Preparation Can sodium chloride be prepared by precipitation ? 3
  4. 4. Salts Preparation – Recap Salts A salt is formed when an acid is neutralised by a base. Acid + Base A salt contains two parts:  Metal part : cation (comes from the base)  Non-metal part : anion (comes from the acid) Salt 4
  5. 5. Salts PreparationMethod of preparing sodium chloride - Titration Action of acid on alkali ACID + ALKALI  SALT + WATER  This process is called neutralisation.  To carry out the neutralisation of the acid and alkali exactly, a method called titration is used. 5
  6. 6. Salts Preparation - TitrationWhen do you choose Titration?- Soluble salts that are: • Group I metal salts i.e. sodium chloride, potassium nitrate, lithium sulfate • Ammonium salts i.e. ammonium chloride, ammonium sulfate-Starting materials used must be an acid and an alkaline-The salts listed in Table 1 can be prepared by the titration method. 6
  7. 7. Salts Preparation - Titration Examples of Salts Prepared by titrationTable 1 Base (alkali) Acid Salt Sodium hydroxide Hydrochloric acid Sodium chloride Potassium hydroxide Hydrochloric acid potassium chloride Sodium hydroxide Sulphuric acid Sodium sulphate Potassium hydroxide Sulphuric acid Potassium sulphate Calcium hydroxide Nitric acid Calcium nitrate Ammonia solution Nitric acid Ammonium nitrate 7
  8. 8. Salts Preparation - Titration1. Pipette 25.0cm3 of dilute hydrochloric acid into a conical flask Dilute2. Add 2-3 drops of hydrochloric acid phenolphthalein into the conical flask 8
  9. 9. Salts Preparation - Titration3. Fill burette with sodium hydroxide and record the initial reading as V1 cm34. Titrate dilute hydrochloric acid with sodium hydroxide from the burette slowly and swirl the solution until it starts to turn pale pink5. Add sodium hydroxide dropwise till solution turn pale pink permanently. This is the end-point of neutralisation.6. Record the final burette reading as V2 cm3. Hence the volume of sodium hydroxide required for complete neutralisation = (V2 -V1) cm3 9
  10. 10. Salts Preparation - Titration Burette V1 V2 Sodium Hydroxide Dilute Sodium chloride hydrochloric and water acid 10
  11. 11. Salts Preparation - Titration7. Pipette 25.0cm3 of hydrochloric acid into another conical flask8. Add (V2 -V1)cm3 of sodium hydroxide from the burette into conical flask9. Heat the sodium chloride solution to evaporate the water till it is saturated10. Allow saturated solution to cool for crystallization to take place11. Filter to collect the sodium chloride crystals12. Dry crystals between a few sheets of filter paper Sodium chloride and water Sodium chloride and water 11
  12. 12. Salts Preparation - TitrationDiscuss how you can prepare ammonium nitrate crystals. - what starting materials to use? - chemical equation? - percentage yield? 12