With the aid of diagram explain Energy profile for catalysed and uncatalysed exothermic and endothermic reaction

Diagram Description:
Imagine a graph with "Potential Energy" on the vertical axis and "Reaction Progress" on the horizontal axis.

• Reactants and Products: Points on the y-axis representing the initial and final energy states.
• Transition State: The highest energy point on the curve between reactants and products.
• Activation Energy ($E_a$): The energy difference between the reactants and the transition state.
• Enthalpy Change ($\Delta H$): The energy difference between the reactants and the products.

1. Exothermic Reaction (Uncatalyzed and Catalyzed):

• Uncatalyzed: The curve starts at a higher energy level (Reactants), rises to a high peak (Transition State), and then drops to a lower energy level (Products).
  • The energy of the Reactants is higher than the Products.
  • $\Delta H$ is the vertical distance from Reactants to Products, and it is negative (energy released).
  • $E_{a,uncat}$ is the vertical distance from Reactants to the high Transition State peak.
• Catalyzed: A second curve starts at the same Reactant energy level and ends at the same Product energy level. This curve has a lower peak (Catalyzed Transition State) than the uncatalyzed one.
  • $E_{a,cat}$ is the vertical distance from Reactants to this lower peak.
  • Crucially, $E_{a,cat} < E_{a,uncat}$.
  • $\Delta H$ remains the same for both catalyzed and uncatalyzed reactions.

2. Endothermic Reaction (Uncatalyzed and Catalyzed):

• Uncatalyzed: The curve starts at a lower energy level (Reactants), rises to a high peak (Transition State), and then ends at a higher energy level (Products).
  • The energy of the Reactants is lower than the Products.
  • $\Delta H$ is the vertical distance from Reactants to Products, and it is positive (energy absorbed).
  • $E_{a,uncat}$ is the vertical distance from Reactants to the high Transition State peak.
• Catalyzed: A second curve starts at the same Reactant energy level and ends at the same Product energy level. This curve has a lower peak (Catalyzed Transition State) than the uncatalyzed one.
  • $E_{a,cat}$ is the vertical distance from Reactants to this lower peak.
  • Crucially, $E_{a,cat} < E_{a,uncat}$.
  • $\Delta H$ remains the same for both catalyzed and uncatalyzed reactions.

In both cases, the catalyst provides an alternative reaction pathway with a lower activation energy, thus speeding up the reaction without changing the overall energy difference between reactants and products ($\Delta H$).