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

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.