Question

A catalyst increases rate of reaction by (a) decreasing enthalpy (b) decreasing activation energy (c) decreasing internal energy (d) increasing activation energy

Short answer

(b) Decreasing activation energy

Step-by-step solution

Understand Catalyst Function

A catalyst is a substance that speeds up a chemical reaction without being consumed by it. It works by providing an alternate pathway for the reaction, which has a lower activation energy than the uncatalyzed pathway.

Define Activation Energy

Activation energy is the minimum energy barrier that must be overcome for a reaction to proceed. A lower activation energy means that more molecules have enough energy to react at a given temperature.

Analyze Provided Options

Read through each option: - (a) Decreasing enthalpy: This does not affect the speed of a reaction but changes energy levels of reactants and products. - (b) Decreasing activation energy: This is the catalyst’s primary role, lowering the energy barrier for the reaction. - (c) Decreasing internal energy: This generally relates to the overall energy in the system but does not specifically address rate. - (d) Increasing activation energy: This would slow down the reaction, opposite to what a catalyst does.

Choose the Correct Answer

Based on the analysis, - Option (b) Decreasing activation energy is the correct choice as a catalyst reduces the energy barrier, increasing the rate of the reaction.

Key concepts

Activation Energy

Activation energy is a foundational concept in chemistry. It refers to the minimum energy that reactant molecules require to successfully undergo a chemical reaction. Think of it as a hill that molecules need enough kinetic energy to climb over before they can proceed with the reaction on the other side.

Molecules always want to achieve stability by reacting and forming products. However, they need to reach a certain energy level to overcome initial hurdles before reacting. This energy barrier exists because initial bonds must be broken before new bonds are formed. Without enough energy, molecules simply can't react, and the process stalls.

• Higher activation energy means fewer molecules can react at a given temperature, leading to slower reaction rates.
• Lower activation energy allows more molecules to surpass this barrier, thus speeding up the reaction.

Understanding activation energy is crucial for controlling how fast or slow reactions proceed.

Chemical Reaction Rate

The chemical reaction rate indicates how fast or slow a reaction takes place. This rate depends on several factors, including the activation energy of the reaction. Essentially, it tells us the speed at which reactants are converted into products over time.

Reaction rates are influenced by: - **Activation Energy**: Lower activation energy results in a higher rate. - **Temperature**: Increasing temperature usually increases the reaction rate, as molecules move faster, gaining energy needed to overcome activation barriers. - **Concentration**: Higher concentrations of reactants can lead to an increased rate since there are more molecules available to collide and react. Unlike activation energy, which is a property of the reaction itself, the reaction rate can be adjusted by changing these external conditions. A clear understanding of it helps in applications across industries, from pharmaceuticals to food production, where controlling reaction speeds is critical.

Catalyst Functionality

Catalysts play a pivotal role in altering the speed of chemical reactions. They are like helpful guides that lead reactant molecules along a path that requires less energy. This path of lower resistance allows more molecules to have enough energy to react.

Key points about catalysts include:

• **They are not consumed**: Catalysts return unchanged after the reaction, ready to assist again.
• **They provide an alternate pathway**: By lowering the activation energy, they enable reactions to occur more quickly and at lower temperatures.
• **Do not change equilibrium**: Only the rate is affected; the final balance between reactants and products remains unchanged.

Catalysts are invaluable in many chemical industries as they reduce the energy required, making processes more energy-efficient. This is particularly important for sustainable and economical chemical manufacturing.