The threshold energy of a chemical reaction depends upon

Options

A. rature of reacting species
B. temperature
C. concentration of species
D. number of collisions

Explanation

To determine what the threshold energy of a chemical reaction depends upon, we can follow these steps:

### Step 1: Understand Threshold Energy
Threshold energy, also known as activation energy, is the minimum energy required for a chemical reaction to occur. It is the energy barrier that must be overcome for reactants to be converted into products.

**Hint:** Recall that threshold energy is related to the energy profile of a reaction, which includes both reactants and products.

### Step 2: Analyze the Energy Profile Diagram
In an energy profile diagram, the x-axis represents the progress of the reaction, while the y-axis represents energy. The threshold energy is the energy level that must be reached for the reaction to proceed.

**Hint:** Visualize the energy changes during a reaction to understand how threshold energy is represented.

### Step 3: Identify Factors Affecting Threshold Energy
The threshold energy depends on:
- The nature of the reacting species: Different substances have different bond strengths and structures, which influence the energy required for the reaction.
- The presence of a catalyst: A catalyst can lower the activation energy, thereby affecting the threshold energy required for the reaction.

**Hint:** Consider how different substances and catalysts can alter the energy landscape of a reaction.

### Step 4: Conclude the Dependencies
From the analysis, we conclude that the threshold energy of a chemical reaction is primarily dependent on:
1. The nature of the reacting species.
2. The presence of a catalyst.

**Hint:** Remember that temperature, volume, concentration, and pressure do not affect the threshold energy.

### Final Answer
The threshold energy of a chemical reaction depends upon the nature of the reacting species and the presence of a catalyst.

**Correct Option:** A (Nature of the reacting species)