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Mrs Teocc

Acids, Bases and Salts. Mrs Teocc. Acids. Strong acids. Weak acids. man-made mineral acids corrosive e.g. sulphuric acid hydrochloric acid nitric acid. found in plants and animals, used in food organic acid not very corrosive

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Mrs Teocc

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  1. Acids, Bases and Salts Mrs Teocc

  2. Acids Strong acids Weak acids • man-made • mineral acids • corrosive • e.g. sulphuric acid hydrochloric acid nitric acid • found in plants and animals, used in food • organic acid • not very corrosive • e.g. ethanoic acid citric acid malic acid Acids

  3. Lemons, limes, oranges, grapefruits - citric acid Grapes – tartaric acid Physical Properties of Acids 1. Acids have a taste. sour

  4. Indicator Colour in acid Blue Litmus Phenolphthalein Methyl orange Physical Properties of Acids 2. Acids can the colour of indicators change Red Colourless Red

  5. Mg + H2SO4 MgSO4 + H2 Chemical Properties of Acids • An acid reacts with a metal to form a salt and hydrogen acid + metal salt + hydrogen • e.g1. zinc + hydrochloric acid • 2. Magnesium + sulphuric acid zinc + hydrogenchloride Zn + 2 HCl ZnCl2 + H2 zinc + hydrogensulphate

  6. Chemical Properties of Acids acid + metal salt + hydrogen

  7. Chemical Properties of Acids acid + metal salt + hydrogen Note: 1. Different metals have different rates of reaction with dilute acids. 2. Sodium , potassium, lithium react explosively with dilute acids. 3.Copper, silver, gold do not react with dilute acids.

  8. Chemical Properties of Acids a salt + water 2. An acid reacts with a base to form acid + base  salt + water e.g. (a) copper(II) + sulphuric oxide acid (b) sodium + hydrochlorichydroxide acid copper(II) + water sulphate CuO + H2SO4 CuSO4 + H2O sodium + water chloride HCl + NaOH  NaCl + H2O

  9. Chemical Properties of Acids The reaction between a base and anacid to produce a salt and water is called neutralisation.

  10. Chemical Properties of Acids 3. An acid reacts with a carbonate to produce a salt, water and carbon dioxide acid + carbonate  salt + water + carbon dioxideeg.(a)magnesium +hydrochloric  carbonate acid magnesium + water + carbon chloride dioxide MgCO3 + 2HCl  MgCl2 + H2O + CO2

  11. White precipitate is formed Chemical Properties of Acids carbonate + acidsalt + water + carbon dioxide

  12. Properties of Acids Summary 1. Acids have a sour taste. 2. Acids change the colour of indicators 3. acid + metal  4. acid + base  5. acid + carbonate  salt + hydrogen salt + water salt + water +carbon dioxide

  13. Explanation for Properties • 1. When an acid dissolves in water, • it undergoes ionisation. • H+ ions and the corresponding acid polyatomic ions are formed. • The properties of an acid are due to the presence of hydrogen ions.

  14. citric acid + water(hydrogen citrate) H+ion + citrate ion sulphuric acid + water(hydrogen sulphate) H+ion + sulphate ion hydrochloric acid + water(hydrogen chloride) H+ion + chloride ion Hydrogen ions and Acids When acid dissolves in water, H+ ions are formed

  15. Hydrogen ions and Acids An acid is a substance that produces hydrogen ions in water

  16. Acids Strong acids Weak acids • all the acid molecules ionise to become ions • most molecules remained unchanged Strength of Acids

  17. Hydrochloric acid Sulphuric acid Nitric acid Ethanoicacid Citric acid Cleaning metallic surfaces before they are painted or coated with other metals Used as an in car batteries, making fertilisers, and plasticsMaking fertilisers and explosives Preserving food and cooking Making health salts Some Uses of Acids

  18. Bases and Alkalis Bases * aqueous ammonia * metal oxides and metalhydroxidese.g. copper (II) oxide, zinc oxide, magnesium oxide, sodium oxide, zinc hydroxide, potassium hydroxide Alkalis * aqueous ammonia * metal hydroxides which are soluble in watere.g. calcium hydroxide, sodium hydroxide,potassium hydroxide

  19. BASES e.g.CuO Bases and Alkalis ALKALIS e.g. NaOH Alkalis are bases but not all bases are alkalis

  20. Physical of Properties of Alkalis • Alkalis feel • Alkalis taste soapy. bitter.

  21. Physical of Properties of Alkalis 3. Alkalischangethe colour of indicators Indicator Colour in Alkali Red litmus Blue Phenolphthalein Pink Methyl Orange Yellow

  22. Chemical Properties of Alkalis 1. An alkali reacts with an acid to produce a salt and water only. acid + alkali salt + watere.g.(a) copper(II) + sulphuricoxideacid (b) sodium + hydrochlorichydroxideacid copper(II) +water sulphate CuO + H2SO4 CuSO4 + H2O sodium + water chloride HCl + NaOH  NaCl + H2O

  23. The reaction between an alkali (base) and an acid to produce a salt and water is called neutralisation.

  24. Chemical Properties of Alkalis 2. An alkali reacts with an ammonium aalt to produce asalt, water and ammonia gas. alkali + ammonium saltsalt + water + ammonia gase.g.ammonium chloride + sodium hydroxide sodium chloride+ water + ammonia NH4Cl + NaOHNaCl + H2O + NH3

  25. Chemical Properties of Alkalis 3. An alkali reacts with a solution of metal saltto form a metal hydroxide. e.g.FeCl3+ 3NaOH Fe(OH)3+ 3NaCl (red-brown ppt) CuSO4 + 2NaOHCu(OH)2 + Na2SO4 (blue ppt)

  26. Properties of Alkalis Summary 1. Alkalis feel soapy. 2. Alkalis change the colour of indicators 3. alkali + acid  4. alkali + ammonium salt  5. alkali + solution of metal salt salt + water. salt + water + ammonia gas. metal hydroxide + salt

  27. Hydroxide ions and Alkalis When an alkali dissolves in water hydroxide ions (OH-) ions are produced. e.g. NaOH  Na+ + OH- KOH  K+ + OH- * Properties of alkalis are due to the presence of hydroxide ions.

  28. Alkalis Strong alkalis Weak alkalis • when the alkali is dissolved in water, all the ions are dissociated • most molecules remained unchanged Strength of Alkalis

  29. OH- OH- Na+ Na+ OH- OH- Na+ Na+ OH- OH- Na+ Na+ Strength of Alkalis Strong alkalis e.g. NaOH  Na+ + OH- KOH  K+ + OH-

  30. Strength of Alkalis Strong alkalis Na+ OH- Na+ OH- e.g. NaOH  Na+ + OH- KOH  K+ + OH- OH- Na+ OH- Na+ Na+ OH- OH- Na+

  31. NH3 NH3 NH3 e.g.NH3 + H2O NH4+ + OH- - Only a small fraction of ammonia molecules form OH- - Most of molecules remained unchanged NH3 NH3 Strength of Alkalis Weak alkalis

  32. e.g.NH3 +H2O NH4+ + OH- - Only a small fraction of ammonia molecules form OH- - Most of molecules remained unchanged Strength of Alkalis NH3 Weak alkalis NH3 NH4+ OH- NH3 NH3

  33. remove grease • neutralise acids e.g. soap, floor cleaners (strong alkali-sodium hydroxide) cleaners for glass windows (weak alkali/ /ammonia) e.g. toothpaste(magnesium hydroxide) antacid(aluminium hydroxide, magnesium hydroxide) Uses of bases/alkalis • mainly for 2 reasons

  34. Uses of Alkalis Alkalis Common names Uses Sodium hydroxidecaustic sodaMaking soap, washing powder, drain cleaner Potassium hydroxide caustic potash Making paint removers dyes for fabric Calcium hydroxide slaked lime Reducing acidity of soil and making mortar Aqueous ammonia Making fertilisers and (Ammonia solution) household cleaning liquids

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