## Reversible Expansion

$\Delta U=q+w$

Abigail Urbina 1K
Posts: 102
Joined: Thu Jul 27, 2017 3:01 am

### Reversible Expansion

Can pressure not be constant when reversible expansion is taking place?

Michelle Dong 1F
Posts: 110
Joined: Fri Sep 29, 2017 7:04 am

### Re: Reversible Expansion

Pressure is usually infinitesimally different between the interior and exterior of the system, and because it is always infinitesimally changing in order to change the volume, that's why we assume that pressure is not constant in a reversible, isothermal reaction. That's why we use the ideal gas equation when deriving the isothermal, reversible equation for work because we're calculating how pressure changes with volume changes. So, in an isothermal, reversible reaction, changing the pressure infinitesimally will change the volume infinitesimally and allow the reaction to reverse back to where it started.