>> Study Material
>> IIT JEE Chemistry
>> Inorganic Chemistry
>> S and P-Block Elements
>> Oxides of Alkali Metals
Oxides of Alkali Metal
Oxides of Sodium:
The possible oxides of Na are Na2O and Na2O2.
It is obtained by burning sodium at 180o C in a limited supply of air or oxygen and distilling off the excess of sodium in vacuum, or by heating sodium peroxide(Na2O2), nitrate(NaNO3) with sodium
2Na + 1/2O2 → Na2O
Na2O2 + 2Na → 2Na2O
2NaNO3 + 10 Na → 6Na2O + N2
It dissolves in water violently yielding caustic soda.
Na2O + H2O → 2NaOH
Sodium Peroxide (Na2O2)
It is formed by heating the sodium metal in excess air or oxygen. The air should be moisture free and temperature required is 300o C.
2Na + O2 → Na2O2
(i) It is pale yellow solid becoming white in air due to the formation of a film of sodium hydroxide and carbonate.
(ii) It dissolves in ice - cold water with hydrolysis, yielding hydrogen peroxide, which decomposes into water and oxygen on warming; whereas it gives oxygen and caustic soda with water at room temperature,
Na2O2 + 2H2O ————→ 2NaOH + H2O2
Na2O2 + 2H2O ———→ 2NaOH + O2
(iii) It dissolves in ice-cold dilute mineral acid yielding H2O2.
Na2O2 + H2SO4 → Na2SO4 + H2O2
Oxides of Potassium
Potassium forms number of oxides namely,K2O,K2O2 and KO2 . Other two oxides can also exist which are K2O3 and KO3
Potassium monoxide (K2O)
It is solid, yellow when hot and white when cold, obtained by heating potassium nitrate with potassium.
2KNO3 + 10K → 6K2O + N2
It dissolves in water to give KOH like Na2O
Potassium Superoxide (K2O2)
Controlled oxidation of potassium in excess air or oxygen at 300o C gives mainly K2O2. It gives H2O2 when dissolves in water.
K2O2 + 2H2O → 2KOH + H2O2
Potassium dioxide (KO2)
It is made by burning potassium in a good supply of air or oxygen. It is powerful oxidising agent. It reacts with water giving both oxygen and hydrogen peroxide.
2KO2 + 2H2O →2KOH + H2O2 + O2
Give some important uses of sodium peroxide.
Important uses of sodium peroxide are:
(i) It is used as a bleaching agent.
(ii) It is used in the manufacture of sodium perborate, benzoyl peroxide.
(iii) It is used for the purification of air in confined spaces such as submarines.
Potassium metal is commercially prepared by the reduction of molten KCl with metallic sodium at 850oC (1,123 K). This method is based upon the following principle:
(A) Sodium is more reactive than potassium at this temperature
(B) Potassium, being more volatile, distils off thus shifting the reaction forward
(C) Sodium prefers to bind to chloride ions in preference to potassium ions
(D) Potassium and sodium form an alloy at this temperature