Short Answer TypeWhen a piece of calcium metal is dropped into a beaker of cold water, a vigorous reaction takes place and the metal gradually disappears to form a white suspension.
(i) Write down the equation for the reaction.
(ii) Why does the solution become milky?
(iii) On filtering, a clear solution is obtained. What is the name of the clear solution?
What is the importance of heavy water with regard to nuclear power generation?
Or
Discuss the importance of heavy water in nuclear reactor.
Knowing the properties of H2O and D2O, do you think that D2O can be used for drinking purposes?
Long Answer TypeHydrogen peroxide (H2O2) can be prepared in laboratory by any one of the following methods:
1. From sodium peroxide. By adding a small amount of sodium peroxide to ice cold water.
In place of cold water, dilute sulphuric acid (20%) can also be used. Sodium peroxide in small amounts at a time is added to cold 20% H2SO4.
On cooling to 271 K, crystals of hydrated sodium sulphate (Na2SO4.10H2O) separate out. The mother liquor contains about 30% hydrogen peroxide.
An alternate method can also be employed for the preparation of hydrogen peroxide using phosphoric acid or sodium dihydrogen phosphate in place of sulphuric acid.
On cooling, crystals of hydrated sodium hydrogen phosphate (Na2HPO4.12H2O) separate out.
2. From barium peroxide. (i) H2O2 is prepared by the action of hydrated barium peroxide on dilute H2SO4.
A thin paste of hydrated peroxide (BaO2.8H2O) is made with ice cold water. It is added very slowly to an ice cold 20% sulphuric acid. Barium sulphate is precipitated and removed by filtration. The filtrate obtained contains about 5% hydrogen peroxide.
Anhydrous barium peroxide is not used in the above method because barium sulphate forms a protective coating on barium peroxide thereby preventing the further reaction.
(ii) An improved method for the preparation of hydrogen peroxide is by treating hydrated barium peroxide with phosphoric acid.
Insoluble barium phosphate is filtered off. The filtrate consists of hydrogen peroxide.
(iii) BaO2 - Carbonic acid process: Hydrogen peroxide is most conveniently prepared by passing carbon dioxide gas into a suspension of barium peroxide in ice-cold distilled water.
Barium carbonate precipitate is removed by filtration. The filtrate obtained is a dilute solution of hydrogen peroxide.
Short Answer TypeWhat precautions are necessary while storing hydrogen peroxide?
Or
Explain why hydrogen peroxide is stored in coloured/plastic bottles.
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