CIE IGCSE Chemistry: Acids, Bases and Salts

Contains all the information you need to know for the CIE IGCSE chemistry exam on topic 8 (acids, bases and salts). It covers everything in the syllabus including different types of oxides, all the tests for ions and gases and colour of compounds you need to know. Please do drop some comments!

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Preview of CIE IGCSE Chemistry: Acids, Bases and Salts

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8. Acids, bases and salts
8.1 THE CHARACTERISITC PROPERTIES OF ACI DS AND BASES
Syllabus Contents
8.1 The characteristic properties of acids and bases
· Describe the characteristic properties of acids as reactions with metals,
bases, carbonates and effect on litmus
· Describe the characteristic properties of bases as reactions with acids
and with ammonium salts and effect on litmus
· Define acids and bases in terms of proton transfer
· Describe the meaning of weak and strong acids and bases
· Describe neutrality and relative acidity and alkalinity in terms of pH
(whole numbers only) measured using Universal indicator paper
· Describe and explain the importance of controlling acidity in soil
ACIDS
Acids are proton donors because they give away H+ ions when reacting with a base.
Acids have a pH number less than 7. It turns blue litmus paper red and universal indicator red.
Acids dissolve in water producing H+ ions and have a sour taste. Strong acids are corrosive.
REACTIONS OF ACIDS WITH METALS
Acid + metal salt + hydrogen
REACTION OF ACIDS WITH BASES
Oxides: acid + metal oxide salt + water
Hydroxides: acid + metal hydroxide salt + water
Carbonates: acid + metal carbonate salt + water + carbon dioxide
BASES
Bases are proton acceptors because they accept H+ ions by bonding them with OH- ions. Bases have a
pH greater than 7 and they turn red litmus paper blue and universal indicator blue.
Bases are made of hydroxide ions and a metal, and can be in the form of metal hydroxide, metal
oxide, metal carbonate, metal hydrogen carbonate, ammonium hydroxide or ammonium
carbonate [note: ammonium ions are not metals, they are exceptions]. Bases have a bitter taste and
strong ones are corrosive.
Not all bases are soluble, some are insoluble.
Soluble bases are also called alkali. Bases react with acids as mentioned in the acids section.
Ammonia is not a metal but it is a base because it accepts protons: NH3 + H+ NH4+
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STRONG AND WEAK ACIDS AND BASES
The amount of H+ ions an acid can give and the amount of OH- ions a base can give determines its
strength. Strong acids give large amounts of ions, they dissociate fully ­ for example, nitric acid,
hydrochloric acid and sulfuric acid are all strong acids, they have a pH of 0 - 3. Weak acids dissociate
partially ­ for example, citric acid, ethanoic acid and carbonic acid (H2CO3) are all weak acids, they
have a pH of 4-6.…read more

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PREPARATION OF SALTS
Syllabus Contents
8.3 Preparation of salts
· Describe the preparation, separation and purification of salts as
examples of some of the techniques specified in section 2.2(b) and the
reactions specified in section 8.1
· Describe the preparation of insoluble salts by precipitation
· Suggest a method of making a given salt from suitable starting material,
given appropriate information
PREPARTION OF SALTS
Salts are ionic compounds which are formed when an acid reacts with a base.…read more

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TITRATION
This reaction is a type of neutralisation without adding any excess solution.
1. Add 25 cm3 of base, for example sodium hydroxide using a volumetric pipette into a flask.
2. Add few drops of phenolphthalein indicator to the flask, this indicator is pink in basic conditions.
3. Fill a burette with an acid (the acid always goes in the burette).
4. Slowly add drops of acid into the flask until the solution turns colourless.…read more

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INDENTIFICATION OF IONS AND GASES
Syllabus Contents
8.4 Identification of ions and gases
· Describe the following tests to identify:
Aqueous cations:
aluminium, ammonium, calcium, copper(II), iron(II), iron(III) and
zinc (Formulae of complex ions are not required.)
Anions:
carbonate, chloride, iodide, nitrate, sulfate
Gases:
Ammonia, carbon dioxide, chlorine, hydrogen, oxygen
TESTS FOR AQUEOUS CATIONS:
METAL IONS
1. Take a small amount of solution.
2. Add few drops of dilute sodium hydroxide or aqueous ammonia.
3.…read more

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TESTS FOR ANIONS:
Anion Test Test result
Carbonate (CO32-) Add dilute acid Effervescence, carbon dioxide
produced
Chloride (Cl-) Acidify with dilute nitric acid, White precipitate
[in solution] then add aqueous silver nitrate
Iodide (I-) (or lead nitrate).…read more

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