What does a particle reservoir mean in thermodynamics? How is it characterised? Heat reservoir for example, is characterised by temperature and supplies or absorbs any amount of heat without changing its temperature. On similar lines, how does a particle reservoir act?
A particle reservoir is a system in chemical equilibrium which is so large that one can extract particles from it without changing its chemical potential. As you see it is quite similar to the heat reservoir.
Note that there is also something called a volume reservoir, acting in the same way (changing volume without affecting pressure). In the literature if all 3 apply, they are called a reservoir in thermodynamic equilibrium. Important to note is that interactions are not allowed to take the reservoir out of its equilibrium state (thermal, mechanical or chemical).