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Acids Strong acids man-made mineral acids corrosive e.g. sulphuric acid hydrochloric acid nitric acid Weak acids found in plants and animals, used in.

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Presentation on theme: "Acids Strong acids man-made mineral acids corrosive e.g. sulphuric acid hydrochloric acid nitric acid Weak acids found in plants and animals, used in."— Presentation transcript:

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

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

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

5 e.g 1. zinc + hydrochloric  acid 2. Magnesium + sulphuric  acid zinc + hydrogen chloride Zn + 2 HCl  ZnCl 2 + H 2 Mg + H 2 SO 4 MgSO 4 + H 2 zinc + hydrogen sulphate Chemical Properties of Acids 1.An acid reacts with a metal to form a salt and hydrogen acid + metal  salt + hydrogen

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

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

8 e.g. (a) copper(II) + sulphuric  oxide acid (b) sodium + hydrochloric  hydroxide acid CuO + H 2 SO 4  CuSO 4 + H 2 O a salt + water a salt + water copper(II) + water sulphate HCl + NaOH  NaCl + H 2 O sodium + water chloride Chemical Properties of Acids 2. An acid reacts with a base to form acid + base  salt + water

9 The reaction between a base and an acid to produce a salt and water is called Chemical Properties of Acids

10 acid + carbonate  salt + water + carbon dioxide eg. (a)magnesium +hydrochloric  carbonateacid acid + carbonate  salt + water + carbon dioxide eg. (a)magnesium +hydrochloric  carbonateacid magnesium + water + carbon chloride dioxide MgCO 3 + 2HCl  MgCl 2 + H 2 O + CO 2 Chemical Properties of Acids An acid reacts with a carbonate to produce 3. An acid reacts with a carbonate to produce a salt, water and carbon dioxide

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

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. H + ions and the corresponding acid polyatomic ions are formed. 2.The properties of an acid are due to the presence of hydrogen ions.

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

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

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

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

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

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

20 Physical of Properties of Alkalis 1.Alkalis feel 2.Alkalis taste soapy. bitter.

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

22 acid + alkali  salt + water e.g. (a) copper(II) + sulphuric  oxide acid acid + alkali  salt + water e.g. (a) copper(II) + sulphuric  oxide acid (b) sodium + hydrochloric  hydroxide acid 1. An alkali reacts with an acid to produce 1. An alkali reacts with an acid to produce Chemical Properties of Alkalis a salt and water only. CuO + H 2 SO 4  CuSO 4 + H 2 O copper(II) +water sulphate sodium + water chloride HCl + NaOH  NaCl + H 2 O

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

24 alkali + ammonium salt  salt + water + ammonia gas e.g. ammonium chloride + sodium hydroxide  Chemical Properties of Alkalis NH 4 Cl + NaOH  NaCl + H 2 O + NH 3 2. An alkali reacts with an ammonium aalt to produce 2. An alkali reacts with an ammonium aalt to produce a salt, water and ammonia gas. sodium chloride + water + ammonia

25 3. An alkali reacts with a solution of metal salt to form a metal hydroxide. e.g. FeCl 3 + 3NaOH  Fe(OH) 3 + 3NaCl (red-brown ppt) Chemical Properties of Alkalis CuSO 4 + 2NaOH  Cu(OH) 2 + Na 2 SO 4 (blue ppt)

26 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  Properties of Alkalis salt + water. salt + water. metal hydroxide + salt salt + water + ammonia gas.

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

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

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

31 Weak alkalis NH 3 e.g. NH 3 + H 2 O NH OH - - Only a small fraction of ammonia molecules form OH - - Most of molecules remained unchanged Strength of Alkalis

32 Weak alkalis NH 3 NH 4 + NH 3 e.g. NH 3 + H 2 O NH OH - - Only a small fraction of ammonia molecules form OH - - Most of molecules remained unchanged OH -

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

34 Alkalis Common names Uses Sodium hydroxide caustic soda Making 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 Alkalis Common names Uses Sodium hydroxide caustic soda Making 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 Uses of Alkalis Uses of Alkalis


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