posted by George2 on .
4) Which of the following is the most effective buffer system for a pH value of 4.45?
a. H2CO3/HCO3- (K1 = 4.4 * 10-7)
b. HCO3-/CO32- (K2 = 4.7 * 10-11)
c. H2S/HS- (K1 = 1.0 * 10-7)
d. HC2O4-/C2O42- (K2 = 5.0 * 10-5)
e. H3PO4/H2PO4- (K1 = 7.5 * 10-3)
I think is D.
Because when i work out , i am uing
-log 5* 10-5 that is close to 4.3. Is that true Can u help me, Thanks
That's right. You want the pKa value to be as close to the desired pH as possible. D fits the closest.