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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