Question

According to the adsorption theory of catalysis, the speed of the reaction increases because (a) adsorption produces heat which increases the speed of the reaction (b) adsorption lowers the activation energy of the reaction (c) the concentration of reactant molecules at the active centres of the catalyst becomes high due to adsorption (d) in the process of adsorption, the activation energy of the molecules becomes large

Short answer

(b) adsorption lowers the activation energy of the reaction.

Step-by-step solution

Understand the Concept

Adsorption is the process where molecules stick to the surface of a solid (such as a catalyst). In catalytic reactions, adsorption is crucial because it can influence the speed of the reaction.

Analyze the Options

Evaluate each option to see which one aligns with the adsorption theory of catalysis. Option (a) suggests adsorption increases temperature, option (b) says it lowers activation energy, option (c) proposes it increases reactant concentration at the active site, and option (d) claims it increases activation energy.

Apply the Theory

Adsorption typically increases the effectiveness of a catalyst by lowering the activation energy required for the reaction, making it easier for reactants to convert into products. This aligns with option (b), which states that adsorption lowers the activation energy of the reaction.

Confirm the Correct Choice

Given the context of adsorption theory, we confirm that the correct choice is option (b). By lowering the activation energy, adsorption allows reactions to proceed more quickly under the same conditions.

Key concepts

Activation Energy

Activation energy is a fundamental concept in chemistry that describes the minimum energy required for a chemical reaction to occur. Imagine this energy as a barrier that reactants must overcome to form products. Without sufficient energy, a reaction cannot proceed. Adsorption theory in catalysis often reduces this activation energy, allowing reactions to happen more easily.

When a catalyst is employed, it provides an alternative pathway for the reaction. This pathway has a lower activation energy compared to the original.

• This doesn't change the energies of the reactants or products.
• It simply makes it easier for molecules to convert from one to another.
• Lower activation energy means reactions can occur at lower temperatures.

With lower activation energy, more reactant molecules can successfully collide with enough energy to surpass the barrier, hence speeding up the reaction process.

Catalyst

A catalyst is a substance that speeds up a chemical reaction without being consumed in the process. It's like having an efficient traffic manager who ensures that cars (reactant molecules) move smoothly and quickly without causing a jam. This is primarily due to how catalysts interact with the reactants: they often adsorb reactant molecules onto their surface.

Adsorption refers to the adherence of reactant molecules to the catalyst's surface. This process increases the concentration of reactant molecules, making it easier for them to collide and react.

Key points about catalysts in reactions:

• They provide a surface for reactants to come together more efficiently.
• They lower the activation energy, as seen in the adsorption theory.
• They emerge unchanged after the reaction, ready to process more reactants.

The effectiveness of a catalyst relies heavily on its ability to adjust the reaction pathway, thereby facilitating the reaction to occur quicker and more efficiently.

Reaction Kinetics

Reaction kinetics is the study of the rate at which chemical reactions occur and the factors influencing these rates. It's like timing how long it takes for a pie to bake and what affects that baking time. Factors such as temperature, concentration of reactants, and presence of a catalyst all play a role in reaction kinetics.

The adsorption theory in catalysis directly impacts reaction kinetics by altering the reaction rate. Let's break it down:

• When a catalyst lowers the activation energy, it speeds up the reaction.
• Adsorption is key because it concentrates reactants at the catalyst's active sites.
• Increased reactant concentration leads to more frequent collisions and faster reactions.

Understanding these kinetics helps chemists manipulate conditions to achieve desired reaction speeds, essential in industrial applications to increase efficiency and productivity.