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12.5 Strong and Weak Acids and Bases

The strength of any acid depends upon the extent to which it gives hydrogen ions in solution. If the concentration of H+ ions in a solution is high the acid is said to be strong.

e.g. HCl, H2SO4, HNO3 etc.

If the concentration of H+ ions in a solution is low the acid is said to be weak.

e.g. Oxalic, tartaric, H2CO3 etc.

Similarly, strong bases are those, which when dissolved in water, readily give OH- ions.

e.g. NaOH, KOH

On the other hand, weak bases are those which when dissolved in water ionize to a small extent (do not readily give OH- ions).

e.g. NH4OH, Mg(OH)2, Ca (OH)2

Properties of Acids and Bases


1) Physical Properties

a) Taste Sour Bitter

b) Conductivity Good conductor Soluble bases are

good conductor

c) Nature Corrosive Slippery to touch


2) Indicator Properties

Color change

a) Litmus Blue to Red Red to Blue

b) Methyl orange Orange to Pink Orange to Yellow

c) Phenolphthalein Colorless Colorless to Pink

3) Chemical Properties

a) Neutralizes bases to give salt Neutralizes acids to

& water give salt & water

NaOH + HCl® NaCl + H2O HBr + KOH ®

KBr + H2O

b) Reacts with carbonates Reacts with CO2 to

to liberate CO2 gas to form carbonates.

K2CO3+2HCL®2KCl + CO2 2NaOH + CO2

+ H2O ® Na2CO3 + H2O

c) Liberates hydrogen Liberates ammonia

with active metals with ammonia salts

Zn + 2HCl ® ZnCl2 + H2

2NH4Cl + Ca(OH)2 ®2CaCl2 + 2H2O + 2NH3

[next page]


12.1 - Lowry and Bronsted Concept
12.2 - Conjugate Acid Base Pairs
12.3 - Amphoteric Substance
12.4 - Lewis Acids and Bases
12.5 - Strong and Weak Acids and Bases
12.6 - Dissociation
12.7 - Ostwald's Dilution Law
12.8 - Hydrogen Ion Concentration : pH
12.9 - Polyprotic Acids
12.10 - Salts
12.11 - Methods of Preparation of Salts
12.12 - Properties of Salts

Chapter 13

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