Consider the reaction. X ( g ) + Y ( g ) − ⇀ ↽ − Z ( g ) K p = 1.00 at 300 K In which direction will the net reaction proceed for the initial conditions [ X ] = [ Y ] = [ Z ] = 1.0 M? net reaction proceeds to the right net reaction proceeds to the left reaction is at equilibrium In which direction will the net reaction proceed for the initial conditions P X = P Z = 1.0 atm, P Y = 0.50 atm? reaction is at equilibrium net reaction proceeds to the left net reaction proceeds to the right

Explanation:

We have in this question the equilibrium

X ( g ) + Y ( g ) ⇆  Z ( g )

With the equilibrium contant Kp = pZ/(pX x pY)

The moment we change the concentration of Y, we are changing effectively the partial pressure of Y since pressure and concentration are directly proportional

pV = nRT ⇒ p = nRT/V and n/V is molarity.

Therefore we can calculate the reaction quotient Q

Qp = pZ/(pX x pY) = 1/ 1  x 0.5 atm = 2

Since Qp is greater than Kp the system proceeds from right to left.

We could also arrive to the same conclusion by applying LeChatelier´s principle which states that any disturbance in the equilibrium, the system will react in such a way to counteract the change to restore the equilibrium. Therefore, by having reduced the pressure of Y the system will react favoring the reactants side increasing some of the y pressure until restoring the equilibrium Kp = 1.