Question
What is activation energy? Explain with the help of graph by suitable example
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Answer
$\rightarrow$ Activation energy can be understood clearly using the formation reaction of hydrogen iodide.
$\ce{\rightarrow H2(g) + I2(g) \rightarrow 2HI(g)}$
$\rightarrow$ According to Arrhenius, this reaction can take place only when a molecule hydrogen and molecule of iodine collide to form an unstable intermediate. It exists for a very short time and then breaks up to form two molecules of hydrogen iodide.
$\rightarrow$ The energy required to form this intermediate, called activated complex $(C),$ is known as activation energy $(E_a).$
$\rightarrow$ Below figure is obtained by plotting potential energy $VS$ reaction coordinate.
Reaction coordinate represents the profile of energy change when reactant change into products.
$\rightarrow$ Some energy is released when the complex decomposes to form products.
So, the final enthalpy of the reaction depends upon the nature of reactants and products.
$\ce{\rightarrow H2(g) + I2(g) \rightarrow 2HI(g)}$
$\rightarrow$ According to Arrhenius, this reaction can take place only when a molecule hydrogen and molecule of iodine collide to form an unstable intermediate. It exists for a very short time and then breaks up to form two molecules of hydrogen iodide.
$\rightarrow$ The energy required to form this intermediate, called activated complex $(C),$ is known as activation energy $(E_a).$
$\rightarrow$ Below figure is obtained by plotting potential energy $VS$ reaction coordinate.
Reaction coordinate represents the profile of energy change when reactant change into products.
$\rightarrow$ Some energy is released when the complex decomposes to form products.
So, the final enthalpy of the reaction depends upon the nature of reactants and products.
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