Explain the catalyst definition and process with examples.

Catalyst is a substance which accelerates the rate of a chemical reaction without undergoing any change in its chemical composition or mass during the reaction. The phenomenon of increasing the rate of a reaction with the help of a catalyst is known as catalysis.

For example, decomposition of potassium chlorate to give dioxygen occurs at high temperature in the range of 653 - 873 K
                                                      
2KClO3  2458_enzyme catalysis3.png  2KCl + 3O2

However, if a small amount of MnO2 is added to KClO3, its decomposition becomes faster and occurs at lower temperature range 473 - 633 K. the mass and chemical composition of MnO2 remains unaltered at the end of reaction. Thus, MnO2 acts as catalyst for the decomposition of KClO3.

Catalytic action

Since the catalysts are not consumed during the reaction, therefore, only a small amount of catalyst is sufficient to catalyse the reaction. According to modern views, a catalyst speeds up the reaction by providing an alternate path of lower activation energy to the reactants. The catalyst lowers the activation energy by interacting with the reactants leading to the formation of some intermediate complex of lower potential energy. In due course, the intermediate complex decomposes to give the products and also the catalyst.

Promotors and poisons

Promotors are the substances which enhance the activity of catalysts. For example, in the Hber's process for the manufacture of ammonia, molybdenum (Mo) is used as promoter which increases the activity of iron (Fe) used as catalyst
                                              
2218_catalysis.png  

Poisons are the substances which decrease the activity of catalyst. For example, during the Rosemnud's reaction involving the hydrogenation of acetyl chloride, Pd is used as catalyst while BaSO4/quinoline acts as poison. This activity of catalyst is purposely decreased to check the reduction of RCOCl to RCHO stage. If this is not done the desired compound RCHO will further undergo reduction to form alcohol RCH2OH.
                                           
1558_catalysis1.png

   Related Questions in Chemistry

  • Q : Adiabatic compression A lean natural

    A lean natural gas is available at 18oC and 65 bars and must be compressed for economical pipeline transportation. The gas is first adiabatically compressed to 200 bars and then isobarically (i.e. at constant pressure) cooled to 25°C. The gas, which is

  • Q : Tetrahedral holes In zinc blende

    In zinc blende structure, zinc atom fill up:(a) All octahedral holes  (b) All tetrahedral holes  (c) Half number of octahedral holes  (d) Half number of tetrahedral holesAnswer: (d) In zinc blende (ZnS

  • Q : Molar and Volumetric flow rate problem

    Cyclohexane (C6H12) is produced by mixing Benzene and hydrogen. A process including a reactor, separator, and recycle stream is used to produce Cyclohexane. The fresh feed contains 260L/min C6H6 with 950 L/min of H2

  • Q : What is protein in Chemistry Illustrate

    Illustrate what is protein in Chemistry?

  • Q : Which is polar HCl or HF Which one is

    Which one is polar HCl or HF?

  • Q : Extensive property Choose the right

    Choose the right answer from following. Which one of the following is an extensive property: (a) Molar volume (b) Molarity (c) Number of moles (d) Mole fraction

  • Q : Molecular mass from Raoults law Provide

    Provide solution of this question. Determination of correct molecular mass from Raoult's law is applicable to: (a) An electrolyte in solution (b) A non-electrolyte in a dilute solution (c) A non-electrolyte in a concentrated solution (d) An electrolyte in a liquid so

  • Q : What is Ideal Mixtures Ideal mixing

    Ideal mixing properties can be recognized in the formation of an ideal gas mixture from ideal gases. Consider the formation of a mixture of gases i.e. a gaseous solution, from two mixtures of pure gases. A useful characterization of an ideal mixture, or soluti

  • Q : Molarity of solution Help me to go

    Help me to go through this problem. When 7.1gm Na2SO4 (molecular mass 142) dissolves in 100ml H2O , the molarity of the solution is: (a) 2.0 M (b) 1.0 M (c) 0.5 M (d) 0.05 M

  • Q : Ions in solution The accuracy of your

    The accuracy of your written English will be taken into account in marking. 1.    (a)   Identify the spectator ions in the following equation                    &nb

©TutorsGlobe All rights reserved 2022-2023.