Simulation · Chemistry · Class 12
What does a catalyst change, and what does it leave alone?
From the lesson Effect of a catalyst in Chemical Kinetics. Change the values and watch what happens.
What does a catalyst change, and what does it leave alone?Chemistry · Class 12
The idea behind it
NCERT §3.4.1
- A catalyst increases the rate of a reaction and is chemically unchanged at the end. MnO₂ speeds up the decomposition of KClO₃: 2KClO₃ → 2KCl + 3O₂.
- A substance added to slow a reaction is not called a catalyst; it is an inhibitor.
- Intermediate complex theory: the catalyst takes part by forming temporary bonds with a reactant to give an intermediate complex, which then breaks up into products and releases the catalyst.
- The catalyst provides a new pathway (mechanism) with a lower activation energy, so a larger fraction of molecules can cross the barrier at the same temperature.
- A small amount of catalyst is enough to change the rate greatly.
- A catalyst does not change ΔG of the reaction. It can speed up only a reaction that is already spontaneous; it cannot make a non-spontaneous reaction happen.
- It lowers the barrier equally for forward and reverse reactions, so equilibrium is reached sooner but the equilibrium constant and the equilibrium composition do not change.