Question

The rate of homogeneous reaction is affected by:

• A. Only temperature
• B. Only pressure
• C. Only concentration of reactants
• D. Temperature, pressure, and concentration of reactants

Hint:

The major factors affecting the rate of a chemical reaction are concentration, temperature, pressure (for gases), catalyst, and surface area. In homogeneous reactions, temperature, pressure, and concentration play significant roles.

Answer 1

The Correct Option is D

Concept: A homogeneous reaction is a reaction in which all reactants and products are present in the same phase, such as all gases or all liquids. The rate of such reactions depends upon factors that influence the frequency and effectiveness of collisions between reacting particles.

Step 1: Effect of concentration of reactants.
According to the collision theory, a chemical reaction occurs when reactant molecules collide with sufficient energy and proper orientation. When the concentration of reactants increases, the number of molecules present per unit volume also increases. As a result:

• The frequency of collisions increases.

• The number of effective collisions increases.

• The rate of reaction increases.
Therefore, concentration directly affects the reaction rate.

Step 2: Effect of temperature.
Temperature is one of the most important factors affecting reaction rate. When temperature increases:

• The kinetic energy of molecules increases.

• Molecules move faster.

• Collisions occur more frequently.

• A larger fraction of molecules possess energy greater than the activation energy.
Hence, the reaction proceeds at a faster rate.

Step 3: Effect of pressure.
Pressure mainly affects gaseous reactions. When pressure is increased:

• Gas molecules are compressed into a smaller volume.

• Effective concentration increases.

• Collision frequency increases.

• The rate of reaction increases.
Thus, pressure also influences homogeneous gaseous reactions.

Step 4: Conclusion.
Since temperature, pressure, and concentration all affect the frequency and effectiveness of molecular collisions, all three influence the rate of a homogeneous reaction. \[ \boxed{\text{Temperature, pressure, and concentration of reactants}} \]