In a reaction involving hydrolysis of an organic chloride in presence of large excess of water eg `RCl + H_2O to ROH + HCl` Which of these is true?

Options

A. Molecularity is 2, order of reaction is also 2
B. Molecularity is 2, order of reaction is 1
C. Molecularity is 1, order of reaction is 2
D. Molecularity is 1, order of reaction is also 1

Answer

To solve the problem regarding the hydrolysis of an organic chloride in the presence of a large excess of water, we will analyze the reaction step by step.

### Step 1: Understand the Reaction
The reaction given is:
\[ RCl + H_2O \rightarrow ROH + HCl \]
Here, \( RCl \) is an organic chloride, and \( H_2O \) is water. The products are \( ROH \) (an alcohol) and \( HCl \) (hydrochloric acid).

### Step 2: Define Molecularity
Molecularity is defined as the number of reactant molecules that come together to react in an elementary reaction. In our case, we have:
- 1 molecule of \( RCl \)
- 1 molecule of \( H_2O \)

Thus, the total number of molecules reacting is:
\[ \text{Molecularity} = 1 (RCl) + 1 (H_2O) = 2 \]

### Step 3: Define Order of Reaction
The order of a reaction is determined from the rate law, which expresses the rate of reaction in terms of the concentration of the reactants. The general form of the rate law can be expressed as:
\[ \text{Rate} = k [RCl]^m [H_2O]^n \]
where \( m \) and \( n \) are the orders with respect to each reactant.

### Step 4: Analyze the Effect of Excess Water
Since water is in large excess, its concentration remains approximately constant during the reaction. Therefore, we can treat the concentration of water as a constant. This leads us to modify the rate law:
\[ \text{Rate} = k' [RCl] \]
where \( k' = k [H_2O] \) (a new constant).

### Step 5: Determine the Order of the Reaction
In the modified rate law:
\[ \text{Rate} = k' [RCl] \]
the exponent of \( [RCl] \) is 1. Therefore, the order of the reaction is:
\[ \text{Order} = 1 \]

### Conclusion
To summarize:
- **Molecularity of the reaction**: 2
- **Order of the reaction**: 1

Thus, the correct statement regarding the reaction is that the molecularity is 2 and the order is 1.