Acids, Bases & Salts

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جمعرات، 28 ربیع الثانی، 1438

Slide 25

SALTS

Topic 10: ACIDS, BASES & SALTS

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When H+ ion of an acid is replaced by a metal ion, a salt is produced e.g.

H2SO4(aq) + 2NaOH(aq) ====== Na2SO4(aq) + 2H2O(l)

Here sodium sulphate (Na2SO4) is the salt formed. Salts are ionic compounds.

Note: Ammonia (NH3) is an unusual base - it does not contain a metal. It forms ammonium salts, containing the ammonium ion, NH4+.

e.g. NH3(aq) + HNO3(aq)  NH4NO3(aq) (ammonium nitrate)

جمعرات، 28 ربیع الثانی، 1438

Slide 26

Methods of making Soluble Salts

Topic 10: ACIDS, BASES & SALTS

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ACID + METAL  SALT + HYDROGEN

2) ACID + BASE  SALT + WATER

3) ACID + CARBONATE  SALT + WATER + CARBON DIOXIDE

ACID + ALKALI  SALT + WATER

DIRECT COMBINATION

جمعرات، 28 ربیع الثانی، 1438

Slide 27

Topic 10: ACIDS, BASES & SALTS

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Method 1 (Acid + Metal)

Not suitable for making salts of metals above magnesium, or below iron/tin in reactivity.

e.g.

Zn + 2HCl ------------------- ZnCl2 + H2

Fe + H2SO4 ---------------- FeSO4 + H2

Method 2 (Acid + Base)

Useful for making salts of less reactive metals, e.g. lead, copper.

e.g.

CuO + H2SO4 ---------------- CuSO4 + H2O

MgO + 2HCl ------------------ MgCl2 + H2O

Add excess base to acid.

جمعرات، 28 ربیع الثانی، 1438

Slide 28

Topic 10: ACIDS, BASES & SALTS

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Method 3 (Acid + Carbonate)

Useful particularly for making salts of more reactive metals, e.g. calcium, sodium.

e.g.

CaCO3 + 2HCl ------------- CaCl2 + H2O + CO2.

Na2CO3 + H2SO4 ------------ Na2SO4 + H2O + CO2.

Method 4 (Acid + Alkali)

This is useful for making salts of reactive metals, and ammonium salts. It is different from methods 1-3, as both reactants are in solution. This means neutralisation must be achieved, by adding exactly the right amount of acid to neutralise the alkali. This can be worked out by titration

e.g.

NaOH + HCl -------------- NaCl + H2O

2NH4OH + H2SO4 ---------------------- (NH4)2SO4 + 2H2O