The value of rate of a pseudo first order reaction depends upon

Options

A. the concentration of both the reactants present in the reaction
B. the concentration of the reactant present small amount
C. the concentration of the reactant present in excess
D. the value of `Delta H` of the reaction.

Answer

To solve the question regarding the value of the rate of a pseudo first-order reaction, we can follow these steps:

### Step 1: Understand the Definition of Pseudo First-Order Reaction
A pseudo first-order reaction is a reaction that appears to be first-order because one reactant is present in a large excess compared to the other reactant. This means that the concentration of the excess reactant remains effectively constant during the reaction.

**Hint:** Remember that in a pseudo first-order reaction, one reactant is in excess, making its concentration constant.

### Step 2: Identify the Rate Law
For a reaction involving two reactants, A and B, where B is in excess, the rate law can be expressed as:
\[ \text{Rate} = k' [A][B] \]
Where \( k' \) is the pseudo rate constant. Since [B] is constant, we can simplify this to:
\[ \text{Rate} = k [A] \]
Where \( k = k' [B] \).

**Hint:** The rate law simplifies when one reactant is in excess, allowing us to focus on the reactant in smaller quantity.

### Step 3: Determine Which Reactant Affects the Rate
In a pseudo first-order reaction, the rate of reaction primarily depends on the concentration of the reactant that is not in excess (the limiting reactant). This is because the concentration of the excess reactant does not change significantly during the reaction.

**Hint:** Focus on the reactant that is present in smaller quantities, as it will dictate the rate of the reaction.

### Step 4: Analyze the Options Given
Given the options in the question, we need to identify which one corresponds to the concentration of the reactant present in smaller amounts.

**Hint:** Look for the option that specifies the concentration of the limiting reactant.

### Step 5: Conclusion
The value of the rate of a pseudo first-order reaction depends on the concentration of the reactant that is present in small amounts. Therefore, the correct answer is the option that states this.

**Final Answer:** The value of the rate of a pseudo first-order reaction depends on the concentration of the reactant which is present in small amount.