2Acids 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
3Physical Properties of Acids 1. Acids have a taste.sourLemons, limes, oranges, grapefruits - citric acidGrapes – tartaric acid
4Physical Properties of Acids 2. Acids can the colour of indicatorschangeIndicatorColour in acidBlue LitmusPhenolphthaleinMethyl orangeRedColourlessRed
5Chemical 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
6Chemical Properties of Acids acid + metal salt + hydrogen
7Chemical 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.
8Chemical 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
9Chemical Properties of Acids The reaction between a base and an acid to produce a salt and water is calledneutralisation.
10Chemical 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
11Chemical Properties of Acids carbonate + acid salt + water + carbon dioxideWhite precipitate is formed
12Properties 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
13Explanation 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.
14Hydrogen 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
15Hydrogen ions and Acids An acid is a substance that produces hydrogen ions in water
16Strength of Acids Acids Strong acids Weak acids all the acid molecules ionise to become ionsWeak acidsmost molecules remained unchanged
17Some 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
18Bases 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
19Bases and Alkalis BASES ALKALIS e.g. NaOH e.g.CuOALKALISe.g. NaOHAlkalis are bases but not all bases are alkalis
20Physical of Properties of Alkalis Alkalis feelAlkalis tastesoapy.bitter.
21Physical of Properties of Alkalis 3. Alkalis change the colour of indicatorsIndicatorColour in AlkaliRed litmusBluePhenolphthaleinPinkMethyl OrangeYellow
22Chemical 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
23The reaction between an alkali (base) and an acid to produce a salt and water is called neutralisation.
24Chemical 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
25Chemical 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)
26salt + 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
27Hydroxide 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.
28Strength of Alkalis Alkalis Strong alkalis Weak alkalis when the alkali is dissolved in water, all the ions are dissociatedWeak alkalismost molecules remained unchanged
29Strength of Alkalis Strong alkalis e.g. NaOH Na+ + OH- KOH K OH-
30Strength of Alkalis Strong alkalis e.g. NaOH Na+ + OH- KOH K OH-OH-Na+OH-Na+Na+OH-OH-Na+
31Strength of Alkalis Weak alkalis e.g. NH3 + H2O NH4+ + OH- - Only a small fraction of ammonia molecules form OH- - Most of molecules remained unchanged
32Strength of Alkalis Weak alkalis e.g. NH3 + H2O NH4+ + OH- - Only a small fraction of ammonia molecules form OH- - Most of molecules remained unchangedNH3NH3
33Uses 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)
34Uses 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