Question

The catalyst used in the preparation of oxygen from hydrogen peroxide is:
A.Manganese dioxide
B.Magnesium oxide
C.Manganese oxide
D.Manganese sulphate

Answer 1

A catalyst is a substance or compound that is added to a reaction, in order to speed up or accelerate the reaction. It increases the rate of reaction without being consumed in the reaction. The catalyst used in the decomposition of hydrogen peroxide acts as an oxidant in many organic reactions.

Complete step by step answer:
Catalysts increase the reaction rate by decreasing the activation energy of the reaction and the process of accelerating a reaction with the help of catalysts is called catalysis.
The preparation of oxygen from hydrogen peroxide follows the reaction,
$2{H_2}{O_2}(aq) \to {O_2}(g) + 2{H_2}O(l)$
Hydrogen peroxide is highly unstable and its decomposition yields oxygen and water with a very high negative value of $\Delta H$, which means that the reaction is highly exothermic. The decomposition is catalyzed by a number of compounds, mostly transition metals such as manganese (Mn), silver (Ag) or platinum (Pt).
The compound of manganese that acts as the catalyst in this reaction is manganese dioxide $(Mn{O_2})$. In addition to manganese(IV) oxide to hydrogen peroxide, bubbles of oxygen are formed and liquid water is formed.
In the absence of catalyst the decomposition of hydrogen peroxide takes place at temperature as high as $400^\circ C$, but in the presence of the catalyst it takes place at room temperature.

Hence option A is correct.

Note:
Manganese dioxide is also known as pyrolusite and is used as a catalyst in an number of reactions due to its high catalytic activity and its stability at temperatures as high as $500^\circ C$, above this temperature decomposition of $Mn{O_2}$ takes place and it converts into $M{n_2}{O_3}$.