Question

Which of the following easily catalyze the decomposition of \[{{H}_{2}}{{O}_{2}}\] when stored?
(i) Rough surface
(ii) sunlight
(iii) Dust particles
(iv) Metals
a) (i) and (ii)
b) (i), (ii) and (iii)
c) (ii) and (iii)
d) All of these

Answer 1

Hint: Hydrogen Peroxide (\[{{H}_{2}}{{O}_{2}}\]) is a colorless liquid, resembling water in many properties. It has physical properties very similar to that of water. It is commonly used in the bleaching process.

Complete answer:
\[{{H}_{2}}{{O}_{2}}\] or hydrogen peroxide acts as a strong oxidizing agent in both acidic and basic mediums. The single bond present between the two oxygen atoms is weak, Therefore, it readily separates into either H and \[H{{O}_{2}}\] or two OHs, resulting in the formation of free radicals meaning they are very reactive. Thus, is a very powerful oxidizing agent. The dissociation can be written as
\[{{H}_{2}}{{O}_{2}}~\left( aq \right)\to {{H}^{+}}+{{O}_{2}}{{H}^{-}}\]

Due to this reason, \[{{H}_{2}}{{O}_{2}}\] is generally sold in a concentration of only 3% in water commercially. This makes it much safer to handle but still, it slowly starts reacting with the water and decomposing. At room temperature, this decomposition reaction takes place at a very slow rate. But when exposed to direct sunlight, decomposition occurs very fast. The UV light coming from the sun rapidly catalyzes the reaction. Therefore, it should be stored in cool places, in dark brown glass bottles. We can write the mechanism as:
\[2{{H}_{2}}{{O}_{2}}+UV\,rays\to 2{{H}_{2}}O+{{O}_{2}}\]
Oxides of various metals can also be used to accelerate the process of decomposition in \[{{H}_{2}}{{O}_{2}}\]. Most commonly used catalysts are Iron oxide, Manganese compounds like Potassium permanganate or Manganese oxide and Silver.


So, the correct option is (ii) and (iv

Note: Bleaching process is the same as oxidation. Hydrogen peroxide is commonly used as a bleach wood pulp to make white paper, and to remove the melanin in hair, giving the blonde effect to hair. It is also used for various disinfection applications.