Question

The terms Q and K describe mass action for reactions at non-equilibrium and equilibrium conditions, respectively. For a forward reaction to being favored in a living cell, which of the following statements must be true?

a. The value of K must be less than that of Q.
b. The value of Q must be less than that of K.
c. No conclusion can be drawn about Q and K for a favorable process.
d. None of the listed statements are true; cells are at equilibrium.

Answer 1

Q should be less than K for the forward reaction to be favoured (option C)

Step-by-step explanation:

Since the standard gibbs free energy is

ΔG = ΔG⁰ + RT*ln Q

where Q= [P1]ᵃ.../([R1]ᵇ...) , representing the ratio of the product of concentration of chemical reaction products P and the product of concentration of chemical reaction reactants R

when the system reaches equilibrium ΔG=0 and Q=Keq

0 = ΔG⁰ + RT*ln Q → ΔG⁰ = (-RT*ln Keq)

therefore the first equation also can be expressed as

ΔG = RT*ln (Q/Keq)

since R and T are always positive :

ΔG<0 if Q<Keq and ΔG>0 if Q>Keq ( thus the reverse reaction is favoured)

therefore Q should be less than K for the forward reaction to be favoured