Question

Acetic acid and water react to form hydronium cation and acetate anion, like this:
HCH3CO2(aq)+H2O-------->H3O(aq)+CH3CO2-(aq)
Imagine 226.mmol of CH3CO2- are removed from a flask containing a mixture of HCH3CO2,H2O ,H3O and CH3CO2- at equilibrium, and then answer the following questions.
1. What is the rate of the forward reaction before any HCH3CO2 has been removed from the flask?
a. zero.
b. greater than zero, but less than the rate of the reverse reaction.
c. greater than zero, and equal to the rate of the reverse reaction.
d. greater than zero, and greater than the rate of the reverse reaction.
2. What is the rate of the forward reaction just after the HCH3CO2 has been removed from the flask?
a. zero.
b. greater than zero, but less than the rate of the reverse reaction.
c. greater than zero, and equal to the rate of the reverse reaction.
d. greater than zero, and greater than the rate of the reverse reaction.
3. What is the rate of the forward reaction when the system has again reached equilibrium?
a. zero.
b. greater than zero, but less than the rate of the reverse reaction.
c. greater than zero, and equal to the rate of the reverse reaction.
d. greater than zero, and greater than the rate of the reverse reaction.
4. How much less hch3co2 is in the flask when the system has again reached equilibrium?
a. none.
b. some, but less than 217mmol.

Answer 1

Answer:

1. c. greater than zero, and equal to the rate of the reverse reaction.

2. d. greater than zero, and greater than the rate of the reverse reaction.

3. c. greater than zero, and equal to the rate of the reverse reaction.

4. b. some, but less than 217 mmol.

Explanation:

Dynamic equilibrium is only attainable in a closed system. When dynamic equilibrium has been attained in a closed system, the rate of forward reaction becomes exactly the same as the rate of reverse reaction.

If the equilibrium of the system is disturbed by removal of one of the products, the equilibrium position will shift to the right thereby yielding more reactants.

After some time, equilibrium is reestablished and rate of forward reaction is once again equal to the rate of reverse reaction.

As the reaction proceeds,  the reactants are used up and their concentration at equilibrium is usually less than the initial concentration at the commencement of the reaction.