Surface Chemistry
10.0 Catalysis
10.0 Catalysis
It is found that the rates of a number of chemical reactions are altered simply by the presence of certain foreign substances. These studies were first made by Berzelius in $1835$. He suggested the name 'catalyst' for such foreign substances.
Catalyst is a substance which can change the speed of a chemical reaction without itself undergoing any change in mass and chemical composition at the end of a reaction and the phenomenon is known as catalysis.
Question 3. Explain the catalytic effect of $Mn{O_2}$ in the decomposition of potassium chlorate.
Solution: When potassium chlorate is heated strongly, it decomposes to give dioxygen. The decomposition takes place at a high temperature in the range $653 - 873\;K$.
\[\begin{array}{c}{2KCl{O_3}}& \to &{2KCl} \end{array}\begin{array}{c}+ &{3{O_2}} \end{array}\]
However, when a small amount of manganese dioxide $\left( {Mn{O_2}} \right)$ is added, the decomposition not only becomes faster but takes place at a much lower temperature, i.e., in the range of $473 - 633\;K$. Moreover, ${Mn{O_2}}$ is found to have same mass and composition at the end of reaction. Thus, ${Mn{O_2}}$ acts as a catalyst for the abov reaction.
