Question

For each of the reactions at constant pressure, determine whether the system does work on the surroundings, the surroundings does work on the system, or essentially no work is performed?

1) The system does work on the surroundings
2) The surroundings does work on the system
3) Essentially no work is performed

Answer 1

In a reaction at constant pressure, work can be done by the system on the surroundings or by the surroundings on the system. Examples include opening a carbonated beverage, filling a flat tire, and a gas can expanding on a hot day.

Step-by-step explanation:

In a reaction carried out at constant pressure, the system does work on the surroundings when it expands against the external pressure. On the other hand, the surroundings does work on the system when the system is compressed by the external pressure. If there is no change in volume or pressure, then essentially no work is performed.

For example, when a carbonated beverage is opened, the system does work on the surroundings because the gas expands and pushes against the atmospheric pressure. When a flat tire is filled, the surroundings does work on the system because the air is compressed and pushes the piston of the pump. When a sealed empty gas can expands on a hot day, essentially no work is performed because there is no external pressure acting on the system.