20 volumes of $H_{2} O_{2}$ means:
(A) 20% of $H_{2} O_{2}$ solution
(B) 20 ml of solution contain 1 g of $H_{2} O_{2}$
(C) 1 ml of solution liberate 20 ml of $O_{2}$ at STP
(D) 20 ml of solution contain 1 mol of $H_{2} O_{2}$

Answer

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Hint: Volume strength refers to the volume of oxygen gas liberated from 1 mole of

H_{2} O_{2}

solution at STP.

Complete step by step answer:
-

H_{2} O_{2}

decomposes to form oxygen and water. The reaction is written as:

H_{2} O_{2} \to H_{2} O + 1 / 2 O_{2}

-When we say 20 volumes of

H_{2} O_{2}

, it means that we are talking about the volume strength of

H_{2} O_{2}

.
Volume strength basically represents the total volume of oxygen gas that would be liberated or obtained at STP from the decomposition of 1 ml of

H_{2} O_{2}

solution.
So, when we are saying that the volume strength of

H_{2} O_{2}

is V, it means that 1 ml of solution will be liberating V ml of oxygen gas (

O_{2}

) at STP.
Here 20 volumes of

H_{2} O_{2}

means that 20 ml of

O_{2}

will be liberated from 1 ml of solution at STP.
So, the correct option is: (C) 1 ml of solution liberates 20 ml of

O_{2}

at STP.

Additional information: Hydrogen peroxide is usually kept stored in dark bottles because it undergoes self decomposition and breaks down into water and oxygen. Although it is non-flammable, it acts as a powerful oxidising agent causing instantaneous combustion on coming in contact with some organic material. It is used for medicinal purposes at very low concentrations of 3% - 9%. It is also used as a bleaching agent for textiles, hair, paper, etc and also as a component of rocket fuel.

Note: Do not confuse yourself by thinking that 20 ml of solution will liberate 1 ml of