Week 2 Achieve #4

[405490807]

HI for this problem I am a little confused on how to obtain the total pressure
At a certain temperature, the given reaction has an equilibrium constant of Kp=417 .

PCl3(g)+Cl2(g)↽−−⇀PCl5(g)

PCl5 is placed in a sealed container at an initial pressure of 0.0370 bar . What is the total pressure at equilibrium?

[OishiBhattacharya2K]

Hi! For this problem, you need to set up an ICE table. Instead of dealing with concentrations, you are dealing with pressure, so set your initial conditions for each reactant/product as such. For this problem, your initial pressures would be 0 for both reactants and 0.0370 for the product. Once you solve for x, find the pressures of each reactant/product. The total pressure is the sum of the pressures of the products/reactants.

[605721741]

A common error made in this question is answering with the value of x instead of answering with the sum of the partial pressures of pcl5, pcl3, and cl2.

[Natalie Flores 1F]

Hi! So for this one I set up an ICE chart with the initial values (all are 0 except PCl5=0.0370). Afterward, the change in each of the reactants is +x and the change for the product is -x. The equilibrium will be the initial value plus the change (x, x, and 0.0370-x, respectively) and once you have those values, plug them into the Kp equation: [PCl5]/[PCl3][Cl2]. Because we already know the Kp value (417) just solve for x using the quadratic equation and plug in x to find the values for each of the reactants and products. The total pressure will be all 3 of those values added up! Hope this helps!!!