Question

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 1

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 ${O_2}$ because this is wrong. The correct statement is that 1 ml of solution will liberate 20 ml of ${O_2}$.
Also always remember that this is true only at STP conditions.