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SALT

SALT. WHO IS SALT ?. WHAT IS SALT ?. WHO IS SALT ?. Ionic compound – formed when the hydrogen ion, H + from an acid is replaced by a metal ion or an ammonium ion, NH 4 +. EXAMPLES :. replace. Na +. Na +. Cl -. Metal ion. Sodium chloride. H. Cl. replace. NH 4 +. NH 4 +. Cl -.

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SALT

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  1. SALT

  2. WHO IS SALT ?

  3. WHAT IS SALT ? WHO IS SALT ? Ionic compound – formed when the hydrogen ion, H+ from an acid is replaced by a metal ion or an ammonium ion, NH4+

  4. EXAMPLES : replace Na+ Na+ Cl- Metal ion Sodium chloride H Cl replace NH4+ NH4+ Cl- Ammonium ion Ammonium chloride

  5. SALTS: ANIONPART COMES FROM THE ACID CATIONPART COMES FROM BASES Common Anions (parent acids) Common Cations Cl- (HCl) Na+ Ca2+ Mg2+ Fe2+ NO3- (HNO3) K+ Al3+ Zn2+ Cu2+ CO32- (H2CO3 NH4+ Pb2+ Fe3+ SO42- (H2SO4)

  6. METAL ION DISPLACE H+ ION IN ACIDS

  7. All nitrate salts ; soluble salts ALL NO3- SOLUBLE SALT

  8. All Na+, K+, NH4+ salts ; soluble salts ALL Na+, K+, NH4+ SOLUBLE SALT

  9. All carbonate salts ; insoluble salts EXCEPT CO32- ALL INSOLUBLE SALT EXCEPT Na+, K+, NH4+

  10. All SO42-, Cl- salts ; soluble salts EXCEPT EXCEPT EXCEPT ALL Pb2+ Ag+ Hg2+ Pb2+ Ca 2+ Ba2+ ALL Cl- SO42- SOLUBLE SALT SOLUBLE SALT

  11. INSOLUBLE SALT SOLUBLE SALT PbSO4 ALL SO42- CaSO4 ALL BaSO4 ALL NO3- CO32- ALL Cl- AgCl ALL PbCl2 Na+, K+, NH4+ CLASSIFICATION OF SALTS

  12. PREPARATION OF SALTS SOLUBLE SALTS INSOLUBLE SALTS NEUTRALISATION OTHER METHOD PRECIPITATION ACID + METAL ACID + ALKALI SOLUBLE SALT + SOLUBLE SALT ACID + METAL OXIDE [SPA] Sodium ,Na+ salts Potassium, K+ salts Ammonium, NH4+ salts INSOLUBLE SALT & SOLUBLE SALT ACID + METAL CARBONATE OTHER SOLUBLE SALTS

  13. PREPARATION OF SOLUBLE SALTS [ SODIUM SALTS / POTASSIUM SALTS / AMMONIUM SALTS ] NEUTRALISATION REACTION EXAMPLE PREPARATION OF POTASSIUM CHLORIDE K H OH Cl K Cl H2O ALKALI ACID SALTS TITRATION METHOD – FIND OUT THE EXACT VOLUME OF ACID REQUIRED TO NEUTRALISE ALKALI. END POINT – POINT WHEN INDICATOR CHANGES COLOUR DURING TITRATION NOTE : CONCENTRATION AND VOLUME OF ALKALI ARE KNOWN.

  14. LET’S DO THIS: PREPARATION OF POTASSIUM CHLORIDE APPARATUS : Pipette 25mL, Burette 50mL, Conical Flask 250mL MATERIALS : Potassium hydroxide 1.0 M, Hydrochloric acid 1.0 M, Phenolphthalein Use a pipette to transfer 25.0 cm3 of potassium hydroxide solution to a conical flask. Add 2 to 3 drops of phenolphthalein Fill a burette with hydrochloric acid and record the initial burette reading. Slowly adding the acid into the conical flask and swirl - until the indicator turns from pink to colourless. Record the volume of acid used. (V cm3) Record the final burette reading to2d.p Colourless KOH turn to pink. Record the burette reading to2d.p

  15. PREPARATION OF POTASSIUM CHLORIDE START OVER AGAIN BUT WITHOUT INDICATOR : To get the pure and neutral salt solution Pipette 25.0 cm3 of the same potassium hydroxide solution into a conical flask. Do not add any indicator. From the burette, add exactly V cm3 of hydrochloric acid to the alkali and swirls and shake well. RECRYSTALLISATION PROCESS [PURIFIED SOLUBLE SALTS] HEATING/EVAPORATE COOLING FILTRATION DRY Solution salt contains impurities continuous with recrystallisation process CRYSTAL SALT

  16. PREPARATION OF SOLUBLE SALTS [ OTHER SALTS EXCEPT Na+, K+, NH4+] OTHER METHOD : DISSOLVE METAL IN ACID Pour 50 cm3of sulfuric acid into a beaker. Warm the acid Use a spatula to add copper(II) oxide powder bit by bit into the acid. Stir the mixture well. Continue adding copper(II) oxide until some of it no longer dissolves (excess unreacted metal) Metal/ metal oxide/ metal carbonate Excess unreactedmetal (residue) Glass rod Acid Evaporating basin with salt solution (filtrate) Solution salt contains impurities continuous with recrystallisation process See the change of metal solid colour and dissolve

  17. RECRYSTALLISATION PROCESS [PURIFIED SOLUBLE SALTS] HEATING/EVAPORATE COOLING Salt solution Evaporating basin Crystal salt

  18. RECRYSTALLISATION PROCESS [PURIFIED SOLUBLE SALTS] FILTRATION DRY CRYSTAL SALT These physical characteristics: • Regulars geometry shapes, such as cubic or hexagonal. • Flat faces, straight edges and sharp angles. • Same angle between adjacent faces. Glass rod Rinse with distilled water Filter Paper Salt Cystals The crystals are filtered and rinsed with a little cold distilled water.

  19. PREPARATION OF SOLUBLE SALTS DISSOLVE SOLUTE IN ACID NEUTRALISATION REACTION 1ST TITRATION WITH INDICATOR FIND VOLUME OF ACID HEATING DISSOLVE METAL IN ACID TRANSFER TO EVAPORATING BASIN 2ND TITRATION NO INDICATOR GET PURE SALT EXCESS METAL NOT DISSOLVE COMPLETE REACT recrystaLlisation HEATING/EVAPORATE COOLING FILTRATION DRY CRYSTAL SALT

  20. PREPARATION OF INSOLUBLE SALTS [ ALL CARBONATE SALTS except Na+/K+/NH4+ ] PbSO4 / CaSO4/ BaSO4/PbCl2/ AgCl] PRECIPITATION REACTION EXAMPLE PREPARATION OF LEAD(II) CHLORIDE Pb NO3 Na Cl Pb Cl2 Na NO3 SOLUBLE SALTS SOLUBLE SALTS INSOLUBLE SALTS DOUBLE DECOMPOSITION METHOD – TWO AQUEOUS SOLUTIONS/SOLUBLE SALTS WERE MIX TOGETHER , INTERCHANGETO PRODUCE TWO NEW COMPOUNDS WHICH ARE AN INSOLUBLESALT (PRECIPITATE)&AQUEOUS SOLUTION (SOLUBLE SALT).

  21. PRECIPITATION REACTION Two aqueous solutions/soluble salts are mixed together [one of the solutions contains the cationsof the insoluble salt] [one of the solutions contains the anions of the insoluble salt] The ions of the two aqueous solutions above interchange to produce two new compounds which is an insoluble salt or precipitate, and an aqueous solution.

  22. PRECIPITATION REACTION Glass rod Glass rod Distilled water Mixture solutions Filter paper Precipitate (residue) Precipitate (residue) Filter funnel Retort stand Aqueous Solution (filterate) Rinse : remove other ions from precipitate Filtration : Remove solution from precipitate FILTRATION RINSE

  23. PRECIPITATION REACTION FLOW CHART : PREPARATION OF INSOLUBLE SALTS Precipitate/Soluble salts Filter paper MIX - STIR TWO SOLUBLE SALTS Dry : Dried by pressing between two pieces of filter paper. FILTRATION REMOVE FILTRATE RINSE REMOVE OTHER IONS DRY PRESS BETWEEN FILTER PAPER

  24. PREPARATION OF SALTS REMEMBER : METAL IONS DISPLACE HYDROGEN IONS IN ACID TO FORM SALTS HCl [H+/Cl-] Hydrochloric acid METAL / AMMONIUM ION Na+ Ca2+ Zn2+ HNO3 [H+/NO3-] Nitric Acid K+ Al3+ Pb2+ H2SO4 [2H+/SO42-] Nitric Acid NH4+ Mg2+ Cu2+ H2CO3 [2H+/CO32-] Nitric Acid Fe3+ Fe2+

  25. SUMMARIES OF REACTION

  26. EXTRA INFO : REMEMBER • Reactive metals aremagnesium, aluminium, and zinc. Unreactivemetals areiron, lead, silver Metal that is less reactive thanhydrogen such as copper, lead and silver willnot react with dilute acid. Soluble salts of sodium, potassium and ammonium can be prepared by the reaction between an acid and alkali.

  27. EXTRA INFO : REMEMBER Metals, metal oxides and metal carbonates are solids that cannot dissolve in water, hence during reaction these solids must be added in excess to make sure all hydrogen ions in acid arecompletely reacted. Excess solid can be then removed through filtration. Unreactive metals such as lead (Pb), copper (Cu), and silver (Ag) cannot react with dilute acid. So to prepare salt contains lead ions (Pb2+), copper ions (Cu2+) or silver ions (Ag+), we must use either oxide powder or carbonate powder only. Impure soluble salt can be purified through crystallization process

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