Question

Why should a bottle of $H_{2}O_{2}$ be cooled before opening it?

Answer 1

Hydrogen peroxide is a highly unstable compound. Even in dilute quantity it decomposes.

This is because of the presence of weak bond between the oxygen atoms. In the presence of sunlight it readily breaks up as follows:

$H_2O_2\rightarrow H^* + HO^*_2 (or)\\H_2O_2\rightarrow 2^*OH$

Since the resultant species are free radicals they are highly reactive.

It is also one of the causes for the formation of photochemical smog. Unburned hydrocarbon fuel molecules are attacked by the free radicals forming molecules. These molecules cause irritation of nose and eyes.

In order to prevent this cause, the bottle containing hydrogen peroxide is cooled before opening to lower the vapour pressure inside the bottle. Hydrogen peroxide liquid remains in its original state.

Answer 2

Hydrogen peroxide is a highly unstable compound. Even in dilute quantity it decomposes.

This is because of the presence of weak bond between the oxygen atoms. In the presence of sunlight it readily breaks up as follows:


\begin{lgathered}H_2O_2\rightarrow H^* + HO^*_2 (or)\\H_2O_2\rightarrow 2^*OH\end{lgathered}H2​O2​→H∗+HO2∗​(or)H2​O2​→2∗OH​

Since the resultant species are free radicals they are highly reactive.

It is also one of the causes for the formation of photochemical smog.Unburned hydrocarbon fuel molecules are attacked by the free radicals forming molecules. These molecules cause irritation of nose and eyes.

In order to prevent this cause, the bottle containing hydrogen peroxide is cooled before opening to lower the vapour pressure inside the bottle. Hydrogen peroxide liquid remains in its original state.