PREPARATION OF BASES
A)Action of oxygen on metals:
Heat any metal like Magnesium, Calcium etc.. in presence of air to give its oxides.
\(
4K + O_2 \xrightarrow{{}}2K_2 O
\) ,
\(
2Cu + O_2 \xrightarrow{{heat}}2CuO
\)
\(
2Mg + O_2 \xrightarrow{{}}2MgO
\)
All metal oxides acts as bases.
B)Action of Steam / water on active metals:
like sodium, potassium and calcium, react with cold water, and form their respective soluble hydroxides along with hydrogen gas.
\(
2Na + 2H_2 O(cold)\xrightarrow{{}}2NaOH + H_2 \uparrow
\)
\(
Ca + 2H_2 O(cold)\xrightarrow{{}}Ca(OH)_2 + H_2 \uparrow
\)
Steam reacts with heated metals like magnesium, aluminium, zinc and iron to form their respective oxides and hydrogen gas.
\(
Mg + H_2 O(steam)\xrightarrow{{heat}}MgO + H_2 \uparrow
\)
\(
3Fe + H_2 O(steam)\xrightarrow{{heat}}Fe_3 O_4 + H_2 \uparrow
\)
\(
NH_3 + H_2 O\xrightarrow{{}}NH_4 OH
\)
C)By dissolving Ammonia gas in water:
Ammonia gas rapidly dissolves in water to form ammonium hydroxide which is a weak base.
D)Action of water on soluble metallic oxides:
Oxides of metals like sodium, potassium and calcium dissolve in water to form their soluble bases.
\(
K_2 O + H_2 O\xrightarrow{{}}2KOH
\)
\(
CaO + H_2 O\xrightarrow{{}}Ca(OH)_2
\)
E)By heating carbonate metals strongly:
All carbonate metals (except ) on heating strongly decompose to form their respective metallic oxides and carbon dioxide gas.
\(
CaCO_3 \xrightarrow{{heat}}CaO + CO_2
\) (gas)
\(
ZnCO_3 \xrightarrow{{heat}}ZnO + CO_2
\)
\(
CuCO_3 \xrightarrow{{heat}}CuO + CO_2
\)