Surface Chemistry

Step 1: Understanding Autocatalysis
Autocatalysis is a reaction where one of the products acts as a catalyst for the same reaction, thereby increasing its rate.

Step 2: Examining the Given Reactions Among the given reactions:
- Reaction (1) is the Haber process, catalyzed by iron and molybdenum, but not autocatalytic.
- Reaction (2) is the decomposition of potassium chlorate, catalyzed by manganese dioxide, not autocatalytic.
- Reaction (3) is hydrolysis of ethyl acetate, where the acetic acid ( ) formed catalyzes further hydrolysis.
- Reaction (4) is a simple precipitation reaction and not autocatalytic.

Step 3: Conclusion Since acetic acid acts as a catalyst in the hydrolysis reaction, it is an example of an autocatalytic reaction.

Step 1: Evaluating Statement-I.
- Gases that can be easily liquefied (like NH , CO , and SO ) have stronger intermolecular forces and are more likely to be adsorbed on solid surfaces.
Thus, Statement-I is correct.

Step 2: Evaluating Statement-II.
- Physisorption involves weak van der Waals forces and has lower adsorption enthalpy than chemisorption, which involves stronger chemical bonds.
Thus, Statement-II is correct.

Statement I: Adsorption of a gas on the surface of charcoal is primarily an exothermic reaction. This statement is correct. Adsorption is generally an exothermic process because the adsorbate molecules lose kinetic energy upon adsorption onto the adsorbent surface.

Statement II: A closed vessel contains O , H , Cl , NH gases. Its pressure is P (atm). About 1 g of charcoal is added to this vessel and after some time its pressure was found to be less than P (atm). This statement is also correct. Charcoal is a good adsorbent. When charcoal is added, it adsorbs some of the gases present in the vessel. This reduces the number of gas molecules in the vessel, leading to a decrease in pressure.

Since both statements are correct, the correct answer is option (1).

Step 1: Understanding Coagulation Coagulation refers to the process of destabilizing a sol by neutralizing the charge on dispersed particles. According to Hardy-Schulze rule, the greater the charge on the oppositely charged ion, the greater its coagulating power.

Step 2: Analyzing the Given Ions Since the sol is positively charged, anions with higher charge will be more effective in coagulation. The given anions have charges as follows: - (Charge: -1) - (Charge: -2) - (Charge: -3) - (Charge: -4)

Step 3: Applying Hardy-Schulze Rule Since has the highest negative charge (-4), it has the maximum coagulating power.