Acids, Bases and Salts - Definitions - Classification - icse class 10 chemistry

 Acids, Bases and Salts - Definitions - Classification - icse class 10 chemistry - Reactions of Bases - Alkalis

Base: A metal oxide or hydroxide which reacts with an acid and produce water and salt only.

e.g CuO, MgO, NaOH etc.

                       CuO   +    H₂SO₄ --> CuSO₄ + H₂O

                       Base         acid                salt        water           

Alkali:  A chemical compound which yields hydroxyl ions as the only negatively charged ions in its aqueous solution.

                       e.g. NaOH, KOH, NH₄OH, etc.

                      

                       NaOH  --> Na⁺  + OH^-

Bases	Alkalis
1.      These are metal oxides or hydroxides	These are metal hydroxides
2.      A few bases are soluble in water.	All the alkalis are soluble in water and produce hydroxyl ions.
3.      e.g. CuO, NaOH, MgO	e.g. NaOH, KOH, NH4OH

 

Strong alkali	Weak alkali
1.      Dissociates completely in water and produces a high concentration of Hydroxyl ions. e.g. NaOH, KOH, LiOH etc 2.      Strong electrolytes	1.      Dissociates partially and produces a low concentration of Hydroxyl ions. e.g. NH4OH, Ca(OH)2   2.      Weak electrolytes

 

Reactions of bases :

1.      Bases react with acids to produce salt and water.

H₂SO₄  + CuO --> CuSO₄ + H₂O

 

2.      Alkalis when heated with Ammonium salts and release Ammonia gas.

NH₄Cl + NaOH -->  NaCl + H₂O + NH₃

3.      Alkalis react with salts to produce precipitates of weak bases.

2NaOH + CuSO₄ --> Na₂SO₄ + Cu(OH)₂ pale blue ppt.

2NaOH + FeCl₃  --> Na₂SO₄ + Fe(OH)₃ reddish brown ppt.