Question

why is , BaO2 is made into paste with water. For the preparation of H2O2​

Answer 1

Hydrogen peroxide can be prepared in the laboratory by the action of ice cold, dilute sulphuric acid on sodium peroxide or hydrated barium peroxide (BaO2​.8H2​O).

A calculated quantity of sodium peroxide is added in small quantities to 20% ice cold solution of sulphuric acid. The reaction is as follows:

Na2​O2​(s)+H2​SO4​→Na2​SO4​(s)+H2​O2​(l)

Most of the sodium sulphate separates out on cooling as crystals of Na2​SO4​.10H2​O.

Thus, 30% of hydrogen peroxide containing small amount of sodium sulphate is obtained.

Barium peroxide is made into a thin paste and added slowly to ice-cold dilute sulphuric acid. The reaction is as follows:

BaO2​(s)+H2​SO4​(aq)→BaSO4​(s)+H2​O2​(l)

Barium sulphate is allowed to settle down as a precipitate and filtered off. The filtrate obtained is a dilute solution of hydrogen peroxide. Phosphoric acid can be used in place of sulphuric acid. Alternatively, carbon dioxide gas may be passed through hydrated barium peroxide paste in ice cold water, in a slow stream.                      

2BaO2​(s)+2H3​PO4​(aq)→Ba(PO4​)2​(s)+3H2​O2​(l)                  

BaO2​(s)+CO2​+H2​O2​→BaCO3​(s)+H2​O2​(l)

The precipitated barium peroxide or barium carbonate is filtered off which leaves hydrogen peroxide.

Answer 2

Answer:

MARK BRAINLIST ANSWER

Explanation:

This prevents the further reaction of the acid i.e. causing the reaction to stop. If however hydrated barium peroxide in the form of this paste is used the water causes to dislodge the insoluble BaSO4 from the surface of BaO2.