Question

Determine the direction of the reaction when (a) Qc > Kc, (b) Qc = Kc, and (c) Qc < Kc. Is there a time when the relationship between Qc and Kc is different than Qc with Kp? Explain.

Answer 1

Qc = the actual quotient given, i.e. what is "seen" right now"

Kc = the value of constant of equilibirum

a)

if Qc > K, then this implies that right now, there are mor products than reactants in equilbirium, so the shift will go toward MORE reactants generation

b)

if Qc = Kc, this is now in equliibirum, no shift will occur

c)

if Qc < Kc, this implies there is much more reactants than products, so expect a shift toward more generation of products.

d)

there is no time realtionship, this is just thermodynamic data that sets concentration equilibirum, no time

e)

Qc relates concentrations, Kp relates pressure

therefore, we need to consider extra mol of gases, since those will increase via:

Kp = Kc*(RT)^dn

where dn = mol of gas in products - mol of gas in reactants