Question

Ammonia and oxygen react to form nitrogen and water, like this:

4NH3(g) + 3O2(g) -» N2(g) + 6H2O(g)
Imagine of 237. mmol of NH3 and 177.75 mmol of O2 of are added to an empty flask, and then answer the following questions.
1. What is the rate of the forward reaction before any NH3 or 02 has been added to 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 NH3 or O2 has been added to 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 at 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 NH is in the flask at equilibrium?
A. Some, but less than.
B. 237. mmol 237. mmol.
C. More than 237. mmol.
D. None.

Answer 1

1. A. Zero.

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. A. Some, but less than 237. mmol.

Step-by-step explanation:

Before reactants are added in a system the rate of reaction is zero. This is because, the initial rate of reaction depends on the concentration of the reacting species in the system.

When the reactants are first added, the rate of forward reaction increases rapidly and is far greater than the rate of reverse reaction.

However, at equilibrium, the rate of forward reaction is equal to the rate of reverse reaction.

At equilibrium, some NH3 has been used and some will still remain in the system because the reaction is reversible.