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ACID AND BASESACID AND BASESACID AND BASESACID AND BASES ACID AND BASESACID AND BASES THE STRENGTH OF ACIDS AND ALKALISTHE STRENGTH OF ACIDS AND ALKALIS CONCENTRATION OF ACIDS ANDCONCENTRATION OF ACIDS AND

ALKALISALKALIS NEUTRALISATIONNEUTRALISATION

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ACID AND BASESACIDSi. Examples: (Chemical formulae of the

acids ) HCl, HNO3, H2SO4, CH3COOH

ii. When acids are dissolved in water,hydrogen atom are released as hydrogen

ions, H+

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DEFINITION OF AN ACID

An acid is a chemical substance whichionises in water to produce hydrogen ions,

H+

Hydrogen chloride molecule, HCl dissolves in water

and ionises to produce a hydrogen ion, H+

HCl H+ + Cl-

The hydrogen ion combines with a water molecule,to form a hydroxonium ion, H3O

+

H+ + H2O H3O+

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Classification of acid

based on its basicity1. Monoprotic acid : HCl and HNO32. Diprotic acid : H2SO4

Basicity of an acid :

The maximum number of hydrogen ions that

is produced when one molecule of the acidionises in water

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Bases and alkalis

A base is a substance that reacts withan acid to form a salt and water

Examples of bases :All metal oxides and metal hydroxide

CuO, MgO, Na2O- Cu(OH)2, Mg(OH)2, NaOH

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Definition of a base

A base is a chemical substance which ionisesin water to produce hydroxide ion, OH-

A base that dissolves in water is called an

Alkali : NaOH, KOH, Na2O, K2O, Ca(OH)2

Ammonia solution, NH3(aq)

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NaOH dissolves in water and

releases its hydroxide ion,OH-

NaOH Na+ + OH-

Ammonia molecule, NH3 dissolves inwater to produce a hydroxide ion,OH-

NH3 + H2O NH4+ + OH-

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Uses of acids, bases and alkali

Laboratary reagents Manufacture and preserve food-benzoicacid, carbonic acid, ethanoic acid, ascorbicacid

Making medicines-magnesiumhydroxide(toothpaste) and Aluminiumhydroxide (gastric pills)

Producing detergents, soaps and shampoo

( sulphuric acid, hyrochloric acid, sodiumhydroxide),

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Role of water and the

properties of acids An acid only shows its acidic

properties when dissolved in water,

- Without water : acid exists asmolecules , no H+ ions present,

- In water : acid ionises to produce

hydrogen ions, H+

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Role of water and the

properties of alkalis An alkali only shows its alkaline

properties when dissolved in water,

- Without water : no free mobile OH-

ions present,- In water : alkali ionises to produce

hydroxide ions, OH-

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The role of water in showing

the properties of acids andalkalis Hydrogen ions ,H+ are responsible for the

acidic properties.

Hydroxide ions, OH-

are responsible forthe alkaline properties.

Water is essential for an acid to ionise toproduce hydrogen ions, H+

Water helps a base to ionise to producehydroxide ion, OH-

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CHEMICAL PROPERTIES

OF ACIDS1. Acids react with bases/alkali to

form salts and water.

2. Acids react with reactive metals toproduce salts and hydrogen gas, H2.3. Acids react with carbonates to

produce salt, water and carbondioxide, CO2

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Reaction of an acid withbases

Sulphuric acid + copper(II) oxide

copper(II) sulphate + water

H2SO4 + CuO CuSO4 + H2O

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Reaction of acid with

reactive metal

Hydrochloric acid + zinc zinc

chloride + hydrogen

2HCl + Zn ZnCl2 + H2

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Reaction of an acid with

metal carbonates Nitric acid + calcium carbonate

calcium nitrate + water +

carbon dioxide

HNO3 + CaCO3 Ca(NO3)2 + H2O

+ CO2

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Experiment today

Reaction of acids investigate the

chemical properties.

Get the salt ( solid/crystal)

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CHEMICAL PROPERTIES

OF ALKALIS1. Alkalis react with acids to form salts and

water.

2. A mixture of an alkali and an ammoniumsalt is heated ammonia gas, NH3produced.

3. Adding and alkali ( OH- ion) to mostcation solutions (metal ions solutions) willgive a precipitate of metal hydroxide