State that a catalyst increases the rate of a reaction and is unchanged at the end of a reaction

Chemical Reactions – Rate of Reaction

What is a Catalyst? 🌱

A catalyst is a substance that speeds up a chemical reaction without being consumed in the process. Think of it as a shortcut that lets the reaction reach its finish line faster, but the catalyst itself stays exactly the same at the end.

How Does a Catalyst Work? ⚡

• It lowers the activation energy \$E_a\$ needed for reactants to form products.
• By providing an alternative reaction pathway, it allows molecules to collide more effectively.
• Because the activation energy is lower, the reaction rate constant \$k\$ increases:
  \$k \propto e^{-E_a/RT}\$.

Key Point: Catalyst is Unchanged After the Reaction

Even though a catalyst speeds up the reaction, it is not used up. After the reaction, the catalyst can be recovered and reused. In chemical equations, we write it on both sides of the arrow:

\$A + B \xrightarrow{\text{catalyst}} C + D\$

Notice the catalyst appears on both sides, indicating it remains unchanged.

Example: Catalytic Converter in Cars 🚗

Cars produce harmful gases like \$NOx\$, \$CO\$, and \$C3H_8\$. Inside the catalytic converter, platinum and palladium act as catalysts:

1. They convert \$NOx\$ into harmless \$N2\$ and \$O_2\$.
2. They reduce \$CO\$ to \$CO_2\$.
3. They oxidise \$C3H8\$ to \$CO2\$ and \$H2O\$.

After the reaction, the metals are still there, ready to work again.

Quick Quiz

1. What is the main role of a catalyst?
2. Does a catalyst get consumed during the reaction?
3. Write a balanced equation showing a catalyst on both sides.

Table: Reaction Rates with and without Catalyst