Final answer:
The Vice President is usually responsible for assisting the president in planning a chapter meeting and taking on leadership roles when needed.
Step-by-step explanation:
The officer responsible for assisting the president and planning a chapter meeting is generally the Vice President. This role typically includes helping the president in their duties and stepping in when the president is unavailable. It's important to note that different organizations may have specific bylaws that assign different responsibilities to officers, but the vice president often serves as the president's primary aide. The Vice President's role is pivotal in maintaining organizational cohesion, facilitating decision-making, and contributing to the overall success of the group under the president's leadership.