Question

The rate of a reaction, on increasing concentration of the reactants (a) increases (b) decreases (c) remains unaltered (d) none of these

Short answer

The rate of a reaction increases with an increase in concentration of the reactants, thus the correct option is (a) increases.

Step-by-step solution

Understanding the reaction rate

The rate of a reaction refers to how quickly the products are formed from the reactants. It depends on several factors such as temperature, catalyst, surface area, and concentration of reactants.

Impact of concentration on reaction rate

The concentration of the reactants majorly impacts the reaction rate. According to the collision theory, an increase in reactant concentrations leads to more molecules per unit volume. This, in turn, increases the frequency of molecule collisions, leading to faster reactions.

Concluding the effect of increased reactive concentration

Considering that the frequency of collisions between reacting molecules increases with an increase in their concentration, it can be inferred that raising the concentration of reactants would increase the rate of the reaction.

Key concepts

Collision Theory

Collision theory helps us understand how chemical reactions occur. Imagine two cars on a collision course: if they meet with the right speed and direction, they crash. Similarly, for a reaction to happen, reactant particles must collide with sufficient energy and appropriate orientation.

• Frequency of Collisions: The more often molecules collide, the more chances they have to react.
• Energy of Collisions: Molecules must collide with enough energy to overcome the activation energy barrier.
• Proper Orientation: Even with energy, a reaction may only occur if the molecules are aligned correctly.

When these criteria are met, a collision can result in a chemical reaction. This process emphasizes that not all collisions result in a reaction. Collisions must be effective, ensuring the particles have the necessary energy and alignment.

Effect of Concentration on Reaction Rate

One of the most significant factors impacting the speed of a reaction is the concentration of the reactants. With more reactant particles in a given volume:

• The probability of effective collisions rises.
• There are more collisions per unit time.
• This results in an increased reaction rate.

By increasing reactant concentration, you effectively increase the chance that molecules will collide with the correct orientation and enough energy. This manifests as an increase in the rate at which products are formed. This aspect of chemistry is crucial in many industrial processes where optimizing the speed of reactions can lead to increased efficiency and output.

Factors Affecting Reaction Rate

Several factors influence how quickly a chemical reaction proceeds. Understanding these is crucial for controlling and optimizing reactions:

• Temperature: Higher temperatures increase particle energy, leading to more frequent and energetic collisions.
• Catalysts: Catalysts lower the activation energy, allowing more collisions to be successful without being consumed in the reaction.
• Surface Area: Increased surface area allows more reactant particles to come into contact, increasing the rate of reaction.
• Concentration: As discussed, higher concentration means more particles in a space, boosting collision frequency and effectiveness.

By manipulating these factors, chemists can control reaction speeds, which is vital in both laboratory settings and industrial applications. This ability to fine-tune reactions allows for innovations in product synthesis and the development of new materials.