Question

Vatting process does not accelerate due to \(\underline{\hspace{2cm}}\)

• A. Temperature
• B. Concentration of alkali
• C. Concentration of reducing agent
• D. Time

Hint:

In kinetics, the rate of a reaction is affected by temperature, concentration of reactants, catalysts, and surface area. Time is the dimension in which the reaction's progress is measured, not a factor that influences its speed.

Answer 1

The Correct Option is D

Step 1: Define the "vatting" process. Vatting is the chemical reduction of an insoluble vat dye into its water-soluble "leuco" form. This reaction is carried out using a reducing agent (like sodium hydrosulphite) in an alkaline solution (like caustic soda). 
 

Step 2: Analyze the factors that affect the rate of a chemical reaction. 
- (A) Temperature: Increasing the temperature generally increases the rate of chemical reactions. The vatting process is often carried out at elevated temperatures (e.g., 50-60°C) to speed it up. So, temperature does accelerate the process. 
- (B) Concentration of alkali: The correct pH and concentration of alkali are essential for the reduction to proceed efficiently. Having the right concentration accelerates the process. 
- (C) Concentration of reducing agent: The reducing agent is a reactant. Increasing its concentration (up to a certain point) will increase the rate of the reduction reaction according to the law of mass action. So, this does accelerate the process. 
- (D) Time: Time is the duration over which the reaction occurs; it is not a factor that changes the rate (speed) of the reaction. A certain amount of time is required for the reaction to complete, but time itself does not accelerate the process. The other factors (temperature, concentration) are what determine how much reaction happens within a given amount of time. 

Conclusion: Temperature and concentrations of reactants are catalysts or drivers of the reaction rate. Time is a result, not a cause of acceleration. Therefore, the vatting process is not accelerated *due to* time.