Question

What effect does a catalyst have on the activation energy of a reaction?

Short answer

A catalyst lowers the activation energy, speeding up the reaction.

Step-by-step solution

Understand Activation Energy

Activation energy is the minimum energy that reactants need to collide with each other in order to transform into products. It is a barrier that must be overcome for a chemical reaction to proceed.

Define Catalyst

A catalyst is a substance that increases the rate of a chemical reaction without being consumed or altered in the process. It provides an alternative pathway for the reaction with a lower activation energy.

Effect of Catalyst on Activation Energy

A catalyst works by lowering the activation energy required for the reaction to proceed. This makes it easier for reactant molecules to reach the transition state and form products. Hence, the reaction occurs at a faster rate.

Key concepts

Activation Energy

Activation energy is the minimum amount of energy that reacting molecules must possess for a reaction to occur. Think of it as a hurdle that reactants must jump over to transform into products. Without sufficient energy, the molecules simply collide without reacting.
For instance, in a combustion reaction, the activation energy is the spark needed to start it. Once that barrier is overcome, the reaction proceeds by itself, often releasing energy in the process. It is crucial to understand that different reactions have different activation energy requirements.
To visualize the concept, imagine rolling a boulder up a hill. The top of the hill represents the activation energy peak. Once the boulder passes this peak, it can easily roll down to the other side, completing the reaction.

Catalyst Function

A catalyst is like a shortcut for a chemical reaction. Without being consumed or permanently changed, it offers an easier path for the reactants to become products by lowering the activation energy needed.
Catalysts work by providing an alternative route for the reaction. For example, in biological systems, enzymes are natural catalysts that speed up biochemical reactions crucial for life. By lowering the activation energy, catalysts make it easier for reactant molecules to reach the transition state where the actual chemical transformation happens.
Importantly, catalysts do not alter the overall energy change of the reaction; they simply make the process quicker by easing the energy barrier. Here are some key points about catalysts:

• They are not consumed in the reaction.
• They lower the activation energy.
• They do not change the reactants or products.
• They can be used repeatedly.

Chemical Reaction Rate

The chemical reaction rate is how fast reactants turn into products. Many factors influence this rate, including temperature, concentration of reactants, and the presence of a catalyst.
When a catalyst is added, the reaction rate increases because the activation energy is lowered. Because the barrier is easier to overcome, more molecules have the energy needed to react in a given time.
For example, in the decomposition of hydrogen peroxide, using manganese dioxide as a catalyst greatly speeds up the reaction, turning the hydrogen peroxide into water and oxygen more quickly. Essentially, by impacting the activation energy, catalysts control how swiftly the chemical transformation occurs. Here are some factors that affect the reaction rate:

• Temperature: Higher temperatures increase molecular motion, helping overcome activation energy barriers.
• Concentration: More reactants mean more collisions, increasing the reaction rate.
• Catalysts: Lower the activation energy and increase the speed of the reaction.