[G O D I V A]

So my book says that (1) if dA < 0 its spontaneous irreversible, and dA = 0 is reversible (equilibrium).

Now it says that (2) for R-->P if dA < 0 the process occurs spontaneously in forward direction and dA>0 spontaneously in reverse direction. 

I dont understand that.  How does the gas constant become pressure.  How come there is no dA > 0 for (1).

[Yggdrasil]

I think R --> P means reactant --> product.

In any case, for a system at constant volume, ΔA < 0 means the process occurs spontaneously in the forward direction, ΔA > 0 means the process occurs spontaneously in the reverse direction, and ΔA = 0 means that the reaction is in equilibrium.