1 / 12

Precipitation reactions

Precipitation reactions. Lesson 3. Precipitation Reactions. Learning Objectives: Describe and explain the tests for ions using sodium hydroxide solution Explain how precipitation reactions can be used to test for some ions.

kimn
Télécharger la présentation

Precipitation reactions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Precipitation reactions

  2. Lesson 3 Precipitation Reactions Learning Objectives: • Describe and explain the tests for ions using sodium hydroxide solution • Explain how precipitation reactions can be used to test for some ions

  3. Silver nitrate and sodium chloride dissolve in water. The solutions are colourless. • Mix the solutions and a white precipitate forms.

  4. A solution of sodium chloride... ... contains sodium ions, Na+, and chloride ions, Cl-.

  5. A solution of silver nitrate... ... contains silver ions, Ag+, and nitrate ions, NO3-.

  6. Mixing the two solutions puts all the ions together. • The silver and chloride ions immediately form a white precipitate of solid silver chloride. • The sodium and nitrate ions remain in solution.

  7. A chemical equation summarises this precipitation reaction. AgNO3(aq) + NaCl(aq)  AgCl(s) + NaNO3(aq) Silver nitrate + sodiumchloride silver chloride + sodiumnitrate

  8. Practical – Testing for Cations A Put 1 cm depth of each of the cation solutions into six different test tubes. B Add a few drops of sodium hydroxide solution to each test tube, and observe what happens. C If a precipitate forms, add a further 1 cm of sodium hydroxide. Again observe any changes that might occur.

  9. Reactions of adding Sodium hydroxide 1. In the cation column what does the number in the bracket correspond to? 2. Which of the cation(s) need further testing?

  10. Further testing Ammonium Ions • Heat the sample with concentrated sodium hydroxide. A smelly alkaline gas (ammonia) will be produced. It turns universal indicator paper blue/purple.

  11. Aluminium and Calcium Ions • If you add excess (more!) sodium hydroxide to a calcium precipitate and aluminium precipitate, different things will happen. • Aluminium precipitate • Calcium precipitate no change, will remain white Will dissolve Excess NaOH Excess NaOH

  12. Task • Worksheet – C3.3 3b ‘More about Cations’ Only questions 1, 2 and 3. DO NOT WRITE ON THE SHEET!

More Related