2 Acids Acids Strong acids Weak acids man-made mineral acids corrosive e.g. sulphuric acid hydrochloric acid nitric acidWeak acidsfound in plants and animals, used in foodorganic acidnot very corrosivee.g. ethanoic acid citric acid malic acid
3 Physical Properties of Acids 1. Acids have a taste.sourLemons, limes, oranges, grapefruits - citric acidGrapes – tartaric acid
4 Physical Properties of Acids 2. Acids can the colour of indicatorschangeIndicatorColour in acidBlue LitmusPhenolphthaleinMethyl orangeRedColourlessRed
5 Chemical Properties of Acids An acid reacts with a metal to forma salt and hydrogenacid + metal salt + hydrogene.g 1. zinc + hydrochloric acid2. Magnesium + sulphuric acidzinc + hydrogen chlorideZn HCl ZnCl H2zinc + hydrogen sulphateMg + H2SO MgSO H2
6 Chemical Properties of Acids acid + metal salt + hydrogen
7 Chemical Properties of Acids acid + metal salt + hydrogenNote: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 + water2. An acid reacts with a base to formacid base salt + watere.g.(a) copper(II) + sulphuric oxide acid(b) sodium hydrochloric hydroxide acidcopper(II) + water sulphateCuO H2SO4 CuSO H2Osodium + water chlorideHCl NaOH NaCl H2O
9 Chemical Properties of Acids The reaction between a base and an acid to produce a salt and water is calledneutralisation.
10 Chemical Properties of Acids 3. An acid reacts with a carbonate to producea salt, water and carbon dioxideacid + carbonate salt + water + carbon dioxide eg. (a)magnesium +hydrochloric carbonate acidmagnesium + water + carbon chloride dioxideMgCO HCl MgCl H2O CO2
11 Chemical Properties of Acids carbonate + acid salt + water + carbon dioxideWhite precipitate is formed
12 Properties of Acids Summary 1. Acids have a sour taste. 2. Acids change the colour of indicators3. acid + metal 4. acid + base 5. acid + carbonate salt + hydrogensalt + watersalt + 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 Hydrogen ions and Acids citric acid water (hydrogen citrate)sulphuric acid water (hydrogen sulphate)hydrochloric acid + water (hydrogen chloride)H+ ion + citrate ionH+ ion + sulphate ionH+ ion + chloride ionWhen 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 Strength of Acids Acids Strong acids Weak acids all the acid molecules ionise to become ionsWeak acidsmost molecules remained unchanged
17 Some Uses of Acids Hydrochloric acid Sulphuric acid Nitric acid Cleaning metallic surfaces before they are painted or coated with other metalsUsed as an in car batteries, making fertilisers, and plastics Making fertilisers and explosivesPreserving food and cookingMaking health saltsHydrochloric acidSulphuric acidNitric acidEthanoic acidCitric acid
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 hydroxideAlkalis* aqueous ammonia* metal hydroxides which are soluble in water e.g. calcium hydroxide, sodium hydroxide, potassium hydroxide
19 Bases and Alkalis BASES ALKALIS e.g. NaOH e.g.CuOALKALISe.g. NaOHAlkalis are bases but not all bases are alkalis
20 Physical of Properties of Alkalis Alkalis feelAlkalis tastesoapy.bitter.
21 Physical of Properties of Alkalis 3. Alkalis change the colour of indicatorsIndicatorColour in AlkaliRed litmusBluePhenolphthaleinPinkMethyl OrangeYellow
22 Chemical Properties of Alkalis 1. An alkali reacts with an acid to producea salt and water only.acid + alkali salt + water e.g. (a) copper(II) + sulphuric oxide acid(b) sodium + hydrochloric hydroxide acidcopper(II) +water sulphateCuO H2SO4 CuSO H2Osodium + water chlorideHCl 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 producea salt, water and ammonia gas.alkali + ammonium salt salt + water + ammonia gas e.g. ammonium chloride + sodium hydroxide sodium chloride + water + ammoniaNH4Cl + NaOH NaCl + H2O + NH3
25 Chemical Properties of Alkalis 3. An alkali reacts with a solution of metal salt to form a metal hydroxide.e.g. FeCl NaOH Fe(OH) NaCl (red-brown ppt)CuSO NaOH Cu(OH) Na2SO (blue ppt)
26 salt + water + ammonia gas. Properties of AlkalisSummary1. Alkalis feel soapy.2. Alkalis change the colour of indicators3. 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 Strength of Alkalis Alkalis Strong alkalis Weak alkalis when the alkali is dissolved in water, all the ions are dissociatedWeak alkalismost molecules remained unchanged
29 Strength of Alkalis Strong alkalis e.g. NaOH Na+ + OH- KOH K OH-
30 Strength of Alkalis Strong alkalis e.g. NaOH Na+ + OH- KOH K OH-OH-Na+OH-Na+Na+OH-OH-Na+
31 Strength of Alkalis Weak alkalis e.g. NH3 + H2O NH4+ + OH- - Only a small fraction of ammonia molecules form OH- - Most of molecules remained unchanged
32 Strength of Alkalis Weak alkalis e.g. NH3 + H2O NH4+ + OH- - Only a small fraction of ammonia molecules form OH- - Most of molecules remained unchangedNH3NH3
33 Uses of bases/alkalis mainly for 2 reasons neutralise acids e.g. toothpaste (magnesium hydroxide)antacid (aluminium hydroxide, magnesium hydroxide)remove greasee.g. soap, floor cleaners (strong alkali-sodium hydroxide)cleaners for glass windows (weak alkali/ /ammonia)
34 Uses of Alkalis Alkalis Common names Uses Sodium hydroxide caustic soda Making soap, washing powder, drain cleanerPotassium hydroxide caustic potash Making paint removers dyes for fabric Calcium hydroxide slaked lime Reducing acidity of soil and making mortarAqueous ammonia Making fertilisers and (Ammonia solution) household cleaning liquids