Acids And Bases

By Tismon Varghese

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contents  Neutralization  Acids in daily life  Common factor present in acids  Reactions of acids  Electricity through acids  Alkalies  Alkalies and bases  Common theories  How to form salts  Dibasic and tribasic acids 2

neutralization Acid + alkali ―> salt + water End point : point at which the reaction is just completed Indicators : substance which give characteristic colour at the end point Examples are • phenolphthalein(strong base Vs strong/weak acids)

pink coloured in alkaline medium and colourless in acid medium • methyl orange(strong acid Vs strong/weak bases )

golden-yellow colour in alkaline medium and pale 3

acids in daily life • we use many acids in our daily life • acids present in different food materials are • Lemon - citric acid • Tomato – oxalic acid • Vinegar – acetic acid • Tamarind – tartaric acid

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common factor present in acids all acids have some common properties due to

the common factor present in it Acids Hydrochloric acid

Chemical formula HCl

Nitric acid

HNO3

Sulphuric acid

H2SO4

Carbonic acid

H2CO3

Phosphoric acid

H3PO4

Common factor present in all acids is hydrogen 5

Reactions of acids Acids and carbonates  Acids reacts with carbonate to form carbon dioxide  In general,

metal carbonate + acid ―> salt + water + carbon dioxide e.g.

CaCO3 + 2 HCl ―> CaCl2 + H2O + CO2

Acids and sulphides  Acids reacts with sulphides to form hydrogen sulphide  When ferrous sulphide is reacts with dil: HCl, hydrogen

sulphide is formed FeS +

2 HCl ―> H2S + FeCl2 6

electricity through acids • The common factor hydrogen, exists as

hydrogen ions(H+) in acids • Ions are electrically charged atoms • Due to the presence of hydrogen ions, acids

can conduct electricity

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alkalies Name and chemical formula of some common

alkalies

alkalies

Chemical formula

Sodium hydroxide

NaOH

Ammonium hydroxide

NH4OH

Potassium hydroxide

KOH

Calcium hydroxide

CaOH

Obviously the common factor present in alkalies is

the hydroxide ions(OH-) 8

alkalies and bases Metals combined with oxygen to form metal

oxides, which are bases Metal oxides reacts with acids to form salt and

water Metal oxides and metal hydroxides neutralizes

acids to form salt and water These oxides and hydroxides which can neutralize

acids are called bases Of these water soluble bases are alkalies 9

common theories  Arrhenius concept: acid is substance that dissociates to give

hydrogen ions when dissolved in water H2SO4 ―> H+ + HSO4HSO4- ―> H+ + SO422H2O + 2H+ ―> 2H3O+ Base is a substance which dissociates in to hydroxide ions when dissolved in water Na(OH)2 ―> Na+ + OH Lowry-Bronsted concept: Acid is substance which has a tendency to donate

a proton And base is a proton acceptor

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How to form salts Acids and alkalies react together to form salts

NaOH + HCl ―> NaCl+ H2O

Na

OH- + H+

OH- + H+

Cl-

NaCl

―>

H2O

+

H2O

Sodium (Na+) ions and chloride (Cl-) ions combine 11 to

Dibasic and tribasic acids Acids having two replaceable hydrogen atoms are

called dibasic acids e.g. H2SO4 Acids having three replaceable hydrogen atoms

are called tribasic acids e.g. H3PO4

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