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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
PROPERTY ACIDS 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
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