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Activation Energy and Catalyst

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Chemical kinetics is the branch of physical chemistry that deals with the rate of chemical reactions. In the year 1889 Swedish scientist named Svante Arrhenius first used the term Activation Energy. Catalyst is something that enhances or increases the rate of a reaction without being consumed in a reaction. Activation energy and catalyst are closely related because the function of the catalyst is to lower down the activation energy so that more particle has enough energy to react. So here we can discuss the topic deeply that helps us to understand more about the concept.

Activation Energy

Activation energy is the minimum energy required to break the bond in a chemical reaction or the minimum energy required to activate the molecule or atom so that it can undergo a chemical reaction.

Representation of Activation energy

Activation Energy can be represented as Ea.

The mathematical expression for the Arrhenius equation is given by,

Representation of Activation energy

Where,

k is the rate of a chemical reaction

A is the pre-exponential factor which is a constant depending on chemicals involved

e is the base of a natural logarithm

Ea is the activation energy

R is the universal gas constant

T is the temperature

Catalyst

A catalyst always functions differently that it enhances a chemical reaction but that itself does not undergo a chemical reaction. It provides an alternative pathway for the reaction.

Examples: Platinum, copper and iron act as a catalyst in many of the chemical reactions

In the human body also catalyst plays an important role. Enzymes act as catalysts and speed up biological reactions.

A catalyst functions to

  • Increase the rate of a reaction.
  • They are not consumed by the reaction
  • A small quantity of catalyst should be able to affect the rate of a reaction
  • Catalyst does not change the equilibrium constant for the reaction

Types of Catalyst

There are mainly 3 types of catalyst

  1. Homogenous catalyst
  2. Heterogenous catalyst
  3. Biocatalyst

Homogenous catalyst

In the homogeneous catalysis, both the reaction and mixture will be in the same phase. Both catalysts and reactants show high homogeneity and thus increases high reactivity and selectivity.

Examples: Transition metals, organometallic complexes

Heterogenous catalyst

In heterogeneous catalysis the catalyst exists in a different phase than reaction mixture. Heterogenous catalyst is used mainly in the preparation of ammonia in the Haber-Bosch process and also used in the industrial process for the easy separation of product and recovery of catalyst

Biocatalyst

Natural proteins (enzymes) or nucleic acids (RNA or ribozymes and DNAs) used to catalyze specific chemical reactions outside the living cells are called biocatalysis.

Examples: Yeast, Bacteria, fungi, etc

Factors affecting Activation Energy

Nature of the reactants

Activation energy can be low and high according to the reactants in a chemical reaction. If the reactant species is ionic in nature the activation energy (Ea) will be low and there will be an attraction between the reactant species. If the reactant is covalent then (Ea) will be high because it requires a high amount of energy to break the bonds

Effect of temperature

For an effective initiation of a chemical reaction, the reactants must move fast and so they can collide with each other with a minimum force to break the bond. The minimum energy corresponds to the activation energy. As we know the kinetic energy of the gas is directly proportional to the temperature and as the temperature increases molecules gain energy and move faster. Thus higher the temperature, the greater will be the movement of a molecule with the necessary activation energy for a reaction.

Effect of Catalyst

Energy diagram is used to illustrate the effect of a catalyst on the activation energy

Effect of Catalyst

Effect of Catalyst

Catalyst decreases the activation energy of the reaction and helps to increase the reaction rate

Examples of Chemical reactions require Activation energy

  • The combustion reaction requires activation energy. Carbon and oxygen combine to form carbon dioxide and transformed the energy
  • Lighting a match which creates friction and turns to heat. The heat thus liberated then produce enough activation energy that allows the chemical on the match to react and ignite the flame

Summary

  • Activation energy is the minimum energy required to break the bond in a chemical reaction
  • Activation energy and catalyst are closely related because the function of the catalyst is to lower down the activation energy
  • Catalyst is a substance that increases the rate of a reaction and provides an alternative pathway with lower activation energy
  • Catalyst can split into a homogenous, heterogeneous and biological catalyst
  • Enzymes are biological catalyst
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Mahesh is leading digital marketing initiatives at RecentlyHeard, a NewsFeed platform that covers news from all sectors. He develops, manages, and executes digital strategies to increase online visibility, better reach target audiences, and create engaging experience across channels. With 7+ years of experience, He is skilled in search engine optimization, content marketing, social media marketing, and advertising, and analytics.

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