Question

1. when is the system at equilibrium said to be dynamic?

a. just prior to equilibrium being established
b. at the start of the process when only reactants are present in the container
c. when it reaches a equilibrium that will shift in response to changes
d. when the system is changing at the macroscopic level with no change at the molecular level
e. when the system reaches constant pressure

Explanation:

To determine when a system at equilibrium is dynamic, we analyze each option:

• Option a: Prior to equilibrium, the system isn't at equilibrium yet, so this is incorrect.
• Option b: At the start with only reactants, equilibrium hasn't been reached, so this is wrong.
• Option c: A dynamic equilibrium can shift in response to changes (Le Chatelier's principle), and at dynamic equilibrium, the forward and reverse reactions occur at equal rates, so the system can respond to changes. This fits the concept of dynamic equilibrium.
• Option d: At dynamic equilibrium, there is change at the molecular level (forward and reverse reactions), while macroscopic properties are constant. So this description is incorrect.
• Option e: Constant pressure doesn't define dynamic equilibrium; equilibrium is about reaction rates and concentrations, not just pressure.

Answer:

c. When it reaches a equilibrium that will shift in response to changes