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Making Salts

Making Salts. Acid + excess insoluble solid. Acid + alkali titration. Acid + reactive metal. Soluble salt. Acid + base. Acid + carbonate. Insoluble salt. Direct combination. Precipitation. Reactions of acids. Neutralisation of: hydrochloric acid gives a chloride

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Making Salts

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  1. Making Salts Acid + excess insoluble solid Acid + alkali titration Acid + reactive metal Soluble salt Acid + base Acid + carbonate Insoluble salt Direct combination Precipitation

  2. Reactions of acids Neutralisation of: hydrochloric acid gives a chloride sulphuric acid gives a sulphate nitric acid gives a nitrate Acid + metal  salt + hydrogen Acid + base*  salt + water Acid + carbonate  salt + water + carbon dioxide *Base: A metal oxide or metal hydroxide. An alkali is a water-soluble base.

  3. Salts A salt is an ionic compound which is neither an acid (containing H+) or a base (containing O2- or OH-). A salt is formed whenever an acid is neutralised. Acids, containing H+ Salts Ionic compounds Bases, containing OH- or O2-

  4. Uses of Salts • Plant fertilisers (NPK) • (NH4)2SO4, NH4NO3, KH2PO4, ……. • Food flavour and preservation • NaCl, KCl, KNO3……. • In toothpaste • NaF • Photographic film • AgCl, AgBr

  5. Salts are important also in: • Proteins and enzymes • The molecules that carry out the chemical reactions of life • DNA and RNA • the molecules of inheritance • Transmission of electrical impulses along nerves

  6. Acid Neutralisation reactions Neutralisation of: hydrochloric acid gives a chloride (containing Cl-) sulphuric acid gives a sulphate (containing SO42-) nitric acid gives a nitrate (containing NO3-) Acid + metal  salt + hydrogen Acid + base  salt + water Acid + carbonate  salt + water + carbon dioxide

  7. Methods of salt making (1) Acid + alkali  salt + water HCl (aq) + NaOH (aq)  NaCl (aq) + H2O (l) Titration of acid against alkali for soluble salts of group 1 metals and ammonium 5 cm3 sodium hydroxide solution was measured using a pipette and transferred to the conical flask. 2 drops of methyl orange indicator were added. Hydrochloric acid was poured into the burette and the starting reading was recorded. The acid was added to the sodium hydroxide, drop by drop, until the indicator turned from yellow to orange (or red). Charcoal was added to the mixture to absorb the indicator and was removed by filtration. Water was evaporated from the filtrate, leaving sodium chloride crystals.

  8. Methods of salt making (2) • Acid + excess insoluble solid • For all other soluble salts • Solid is either a moderately reactive metal, a base or a carbonate • Excess solid to react with all the acid • Removed by filtration

  9. Methods of salt making (3) • Precipitation reactions • To make insoluble salts • 2 solutions each containing one of the ions in the salt are mixed. • Salt is precipitated • Salt is filtered, residue is washed on filter paper and dried.

  10. Methods of salt making (4) • Direct combination of the elements sodium (l) + chlorine (g)  sodium chloride (s) 2 Na (l) + Cl2 (g)  2 NaCl (s) aluminium (s) + bromine (l)  aluminium bromide (s) 2 Al (s) + 3 Br2 (l)  2 Al Br3 (s)

  11. Methods of salt making (1) (a) barium hydroxide (aq) + nitric acid (aq) 2 Ba(OH)2 (aq) + HNO3 (aq) barium nitrate (aq) + water (l) Ba(NO3)2 (aq) + H2O (l) 2

  12. Methods of salt making (1) (b) ammonium carbonate (aq) + sulphuric acid (aq) (NH4)2CO3 (aq) + H2SO4 (aq) ammonium sulphate (aq) + water (l) + carbon dioxide (g) (NH4)2SO4 (aq) + H2O (l) + CO2 (g)

  13. Methods of salt making (1) (c) ammonium hydroxide (aq) + nitric acid (aq) NH4OH (aq) + HNO3 (aq) ammonium nitrate (aq) + water (l) NH4NO3 (aq) + H2O (l)

  14. Methods of salt making (1) (e) potassium hydroxide (aq) + nitric acid (aq) KOH (aq) + HNO3 (aq) potassium nitrate (aq) + water (l) KNO3 (aq) + H2O (l)

  15. Methods of salt making (2) Acid + insoluble base  salt + water H2SO4 (aq) + CuO (s)  CuSO4 (aq) + H2O (l)

  16. Methods of salt making (2) (g) calcium (s) + nitric acid (aq) 2 Ca (s) + HNO3 (aq) calcium chloride(aq) + hydrogen (g) Ca(NO3)2 (aq) + H2 (g)

  17. Methods of salt making (2) (f) iron (s) + sulphuric acid (aq) Fe (s) + H2SO4 (aq) iron (II) sulphate (aq) + hydrogen (g) FeSO4 (aq) + H2 (g)

  18. Methods of salt making (2) (d) calcium carbonate (s) + nitric acid (aq) 2 CaCO3 (s) + HNO3 (aq) calcium nitrate (aq) + water (l) + carbon dioxide (g) Ca(NO3)2 (aq) + H2O (l) + CO2 (g)

  19. Acid + metal  salt + hydrogen Magnesium + hydrochloric acid  magnesium chloride + hydrogen Mg (s) + 2 HCl (aq)  MgCl2 (aq) + H2 (g) Mg (s) + 2 H+ 2 Cl- (aq)  Mg2+ 2 Cl- (aq) + H2 (g) 2 e- copper + hydrochloric acid  no reaction Cu (s) + 2 HCl (aq) Cu (s) + 2 H+ 2 Cl- (aq)

  20. Metal Reactivity Series Potassium Sodium Lithium Calcium Magnesium Zinc Iron Lead Hydrogen Copper Silver Gold Platinum React with cold water React with dilute acids and steam Reactivity Do not react with dilute acids and steam

  21. Acid + base  salt + water Sulphuric acid + copper oxide  copper sulphate + water H2SO4 (aq) + CuO (s)  CuSO4 (aq) + H2O (l) 2 H+ SO42- (aq) + Cu2+ O2- (s)  Cu2+ SO42- (aq) + H2O (l) Sulphuric acid + copper hydroxide  copper sulphate + water H2SO4 (aq) + Cu(OH)2 (s)  CuSO4 (aq) + 2 H2O (l) 2 H+ SO42- (aq) + Cu2+ 2 OH- (s)  Cu2+ SO42- (aq) + 2 H2O (l)

  22. Carbonic acid • H2CO3 (aq) • 2 H+ CO32- (aq) • Present in fizzy drinks: H2CO3 (aq)  CO2 (g) + H2O (l)

  23. Acid +carbonate  salt + water + carbon dioxide Sulphuric acid + nickel carbonate  nickel sulphate + water + carbon dioxide H2SO4 (aq) + NiCO3 (s)  NiSO4 (aq) + H2O (l) + CO2 (g) 2 H+ SO42- (aq) + Ni2+ CO32- (s)  Ni2+ SO42- (aq) + H2O (l) + CO2 (g) + H2CO3 (aq)

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