Question

Explain how thermodynamics relates non-expansion work to a change in composition of a system.

Answer 1

SOLUTION:

The change in composition may be employed to perform work. For example in Galvanic cells the change in coposition results in usefull wor; Mathemetical relation between the composition and work ca be arrived at as follows

ΔG = VdP - SdT + µ_Adn_A + µ_Bdn_B + .......

At constant temperature and pressure

ΔG = µ_Adn_A + µ_Bdn_B + .......

Work done by the system is equal to change in Gibbs energy, Hence we can write as

W_{non exp} = µ_Adn_A + µ_Bdn_B + .......

Above equation relates non expansion work to composition of the system.

µ_i = Chemical potential of component i and dn_i = Change in composition of i.