Work by a Gas

The Work by a Gas calculator computes the amount of energy acting on an amount of gas based on external pressure and the change in volume.

INSTRUCTIONS: Choose units and enter the following:

• (P)  External Pressure on System
• (V_f)  Final Volume
• (V_i)  Initial Volume

Work (W):  The calculator returns the work done by or on the system in Joules. However, this can be converted to compatible units (e.g. N•m) via the pull-down menu.

The Math / Science

The  Work by a Gas calculator computes the amount of force it takes to displace an object, in chemistry's case the force is the external pressure of molecules exerting force on the system, and the displacement is the change of volume. Work equation is used in the Internal energy equation^[3].  If work is positive then the system does the work, if the work is negative then the work is done on the system. 

The work equation is calculated by 

     W = -P * ΔV

where :

• W is the work done by or on the system in units of (Joules)
• P is the external pressure on the system in units of (Pa)
• ΔV is the change in volume^[2] in units of (m³)

A more general representation of this work= force*distance relationship integrates the force applied over the distance spanned.

Gas and Energy Calculators

• Enthalpy
• Internal energy - Computes the internal energy based on the change in heat energy and work
• Enthalpy of change for the reaction

Supplement Material

• HyperPhysics: work
• Khan Academy: Introduction to work and energy
• UC Davis: Work

References

[1]https://en.wikipedia.org/wiki/Work_(physics)#Work_by_a_gas

[2] Whitten, et al. 10th Edition. Pp. 571

[3]https://en.wikipedia.org/wiki/Internal_energy