[equivalently]

PCl5(g) <=> PCl3(g) + Cl2(g)

A system is prepared by placing equimolar amounts of the three gases from the equation above in a suitable container with constant volume. Equilibrium is established at 546 K.


When equilibrium is established, how does [PCl3] compare to [Cl2]?

I understand that equilibrium will shift into the direction that something is lost, but what happens when there is nothing being gained or lost. Instead, only equilibrium is present how does that affect the concentrations? I also understand that if an equilibrium reaction is stressed with pressure it will shift to the side with lease number of moles in this case, the left. Does pressure have anything to do with it?


- Thanks for the help

[Borek]

Please read forum rules.

[xiankai]

the system is not at equilibrium initially. do remember you do not know the value for K_c.

question asks for the concentration of PCl₃ compared to that of Cl₂; bearing in mind that the equilibrium position of the reaction is either to the left or right for a certain temperature, for simplicity assume that the initial system will progress in one direction to the equilibrium direction.

at equilibrium, will [PCl₃] be more than/less than/equal to [Cl₂]?

I also understand that if an equilibrium reaction is stressed with pressure it will shift to the side with lease number of moles in this case, the left. Does pressure have anything to do with it?

moles of gaseous substances, you mean. you are correct. however since there is constant volume, and no other gases are added in, pressure can be assumed to be constant.