In: Chemistry
To the nearest tenths, what is the equilibrium constant for the enzymatic hydrolysis of 0.1 M A-O-PO32- to A-OH and inorganic phosphate (where A is some generalized molecule) given that 0.04% of the original A-O-PO32- remained after reaching equilibrium and the activity of water is unity. Assume a pH of 7.0.
In firt place, it should be defined the equilibrium constant in molar concentration because the only clue in this exercise is the initial concentration [A-O-PO32-]= 0.10M.
KM = {[AOH][PO43-] }/[A-O-PO3 2-]
Next, it should be written this reaction to make its equilibrium scheme:
A-O-PO32-(ac) + H2O(l) => AOH(ac)+ PO43-(ac)
Water concentration remains constant and the sheme is:
[A-OPO32- ] (M) | [AOH] (M) | [PO43-] (M) | |
Initial | 0.10 | 0.00 | 0.00 |
Change | -x (because it decreases) | +x (because it increases) | +x (because it increases) |
At equilibrium concentration | 0.10-x | +x |
+x |
If the initial concentration of A-O-PO32- is 0.10M and remains 0.04% at equilibrium, it must be calculated its final concentration.
0.10M _________100%
y __________0.04%
y= 0.04x0.10M/100= 4.0.10-5M
0.10M - x = 4.0.10-5M
-x = (4.0.10-5- 0.10)M
-x= -0.09996M
x= 0.09996M
For our convenience; it should be defined the KM again but using x at the equilibrium.
KM= x.x/(0.10-x)
KM = x2/(0.10-x) x= 0.09996M
KM= 0.099962M2/(0.10-0.09996)M= 249.8M
Finally: KM= 249.8 M