Question

Which of the following catalysis is an example of negative catalysis?
$A.\;\;2S{O_2} + \;{O_2}\xrightarrow{{{V_2}{O_5}}}2S{O_3}$
$B.\;\;CHC{l_3} + \;{O_2}\xrightarrow{{Alcohol}}2COC{l_2} + 2HCL$
$C.\;\;2KCl{O_3}\xrightarrow[\Delta ]{{Mn{O_2}}}2KCl + \;3{O_2}$
$D.\;\;CO + \;3{H_2}\xrightarrow{{Ni}}C{H_4} + {H_2}O$

Answer 1

Hint: - A catalyst is a substance that can be added to a reaction to increase the reaction rate without getting consumed in the process.

Complete step-by-step answer:
Catalysts are defined as substances which alter the rate of reaction by changing the path of reaction. Many times, a catalyst is used to increase the rate of the reaction. When we elaborate about catalysts then we come to know that they are used to break or rebuild the chemical bonds between the atoms which are present in the molecules of different elements or compounds.
In simple terms catalysts encourage molecules to react and make the whole reaction process easier and efficient. Catalyst alters the rate of reaction by altering activation energy of reaction.
Important characteristic features of catalysts are
1. Catalyst does not initiate a chemical reaction.
2. They do not get consumed in the reaction.
3. They tend to react with reactants to form intermediates and at the same time facilitate the production of the final reaction product.
4. After the whole process is complete catalysts can regenerate.
5. Catalysts can be either solid, liquid or gaseous catalysts.

Types of Catalysts: -
Positive Catalysts
Catalysts which increase the rate of a chemical reaction.

Negative Catalysts
Catalysts which decrease the rate of reaction.

Promoter or Accelerators
A substance which increases the catalyst activity are known as Promoters or accelerators.

Here in options A, C, D there are positive catalysts but in option B alcohol ${C_2}{H_5}OH$ is a negative catalyst. Hence option B is the correct answer as alcohol ${C_2}{H_5}OH$ is catalyst for oxidation of $CHC{l_3}$ which prevents reaction of chloroform with oxygen to give $COC{l_2}$​.

Note: In such types of problems we must know the definition of Catalyst and its types. Also, what is the function of various types of catalyst. Positive Catalysts are catalysts which increase the rate of a chemical reaction and negative. Catalysts which decrease the rate of reaction, they are also known as retarder.