Question

using the following balanced chemical equation: PCL5 -> PCL3 + CL2 and knowing that Keq = 7.9, [PCL3] = 0.054M and [CL2] = 0.34M
a. write the Keq expression for the reaction
b. find the [PCL5]
c circle the correct answer: the reaction favored is the (forward, reverse)

Answer 1

Answer:

see explanations

Explanation:

              PCl₅  =>     PCl₃     +     Cl₂

C(eq):   [PCl₅]       0.054M        0.34M

a.  Keq = [PCl₃][Cl₂]/[PCl₅]

b.  7.9 = (0.054)(0.34)/[PCl₅] => [PCl₅] = (0.054)(0.34)/(7.9) = 0.0023M

c.  If [PCl₃] = 0.054M; [Cl₂] = 0.34M and [PCl₅] = 0.0023M then the reaction is at equilibrium and will not shift forward or in reverse. In order to determine if reaction is not at equilibrium, a set of concentration values needs to be given in problem, used to calculate Qeq and compared to the given Keq value.  The following defines direction of shift ...

Keq  <  Qeq  =>  rxn shifts left

Keq  =  Qeq  =>  rxn is at equilibrium (no shift)

Keq  >  Qeq  =>  rxn shifts right

NOTE: If Keq is listed first followed by Qeq in the above conditions, the inequality symbol indicates direction of shift.