Question

Consider the reaction X ---> Y in a cell at 37 degrees Celcius. At equilibrium, the concentrations of X and Y are 50 micrometers and 5 micrometers, respectively. Use this information and your knowledge of the relationships between deltaG, and deltaG^o , and the equilibrium constant (K) to answer questions a-c.

a) What is the value of K for this reaction?

b) What is the value of the standard free energy? is the reaction X-->Y and energetically favorable or unfavorable reaction under standard conditions?

c) Imagine circumstances in which the concentration of X is 1000 micrometers and that of Y is 1 micrometer. Is conversion of X to Y favorable? Will it happen quickly?

Answer 1

a) What is the value of K for this reaction?

equilibrium constant K = [Y] / [X] = 5 / 50 = 0.1

b)

deltaG^o = - R T ln K

             = - 8.314 x 10^-3 x 310 x ln 0.1

             = 5.93 kJ

the reaction X-->Y is unfavorable reaction under standard conditions. because delta Go is positive.

(c)

equilibrium constant K = [Y] / [X] = 1 / 1000 = 0.001

no. it is unfavourable. because K value is less than 1