CH3COOC2H5(1) + H2O(1) ⇌ CH 3COOH (aq) + C 2H 5OH (aq) The purpose of H+ in the reaction above is to

Analysis of the Question

The reaction provided is the acid-catalyzed hydrolysis of an ester (ethyl ethanoate). You are asked to identify the specific role of the hydrogen ion ($H^+$) in this chemical equation.

Concept Explanation

In organic chemistry, esters react with water to form a carboxylic acid and an alcohol. This process is known as hydrolysis.

1. Nature of the Reaction: The hydrolysis of an ester is a relatively slow process at room temperature.
2. Role of the Catalyst: The $H^+$ ion acts as a catalyst. A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. It does this by providing an alternative reaction pathway with a lower activation energy.
3. Equilibrium: While catalysts speed up reactions, they do not change the position of the equilibrium (i.e., they do not increase the yield of the products; they only help the system reach equilibrium faster).

Step-by-Step Solution

• Step 1: Identify the reactants and products. We have an ester ($CH_3COOC_2H_5$) reacting with water ($H_2O$) to produce ethanoic acid ($CH_3COOH$) and ethanol ($C_2H_5OH$).
• Step 2: Recognize the catalyst. The $H^+$ represents an acid catalyst (such as dilute $H_2SO_4$ or $HCl$).
• Step 3: Evaluate the options based on the definition of a catalyst: • A: Incorrect. Catalysts do not increase the yield (the amount of product formed at equilibrium); they only speed up the attainment of that equilibrium. • B: Incorrect. While acids affect pH, the primary purpose of adding $H^+$ to this specific reaction is to speed it up. • C: Correct. The $H^+$ ion lowers the activation energy, thereby increasing the rate at which the ester is hydrolyzed into acid and alcohol. • D: Incorrect. A catalyst increases the rate of both the forward and reverse reactions equally.

Conclusion

The $H^+$ ion acts as a catalyst to speed up the hydrolysis process. Therefore, its purpose is to increase the rate of the reaction.

Exam Tip: Whenever you see a small $H^+$ written above the arrow in a chemical equation, always associate it with catalysis (speeding up the reaction). Never confuse a catalyst with a reactant that increases yield!