Asked by Sara
If you make up a solution of 100 mL of 0.1 M HEPES in the basic form, what will be the pH?
I have no idea where to even start...
I have no idea where to even start...
Answers
Answered by
DrBob222
Just treat it as you would 0.1M soln of NH3.
For the sake of typing let's call the basic form of HEPES, BH2. In water solution this will ionize as
............BH2 + HOH ==> BH3^+ + OH^-
initial....0.1M.............0......0
change......-x.............x.......x
equil......0.1-x............x.......x
Kb = (BH3^+)(OH^-)/(BNH2)
Substitute from the ICE chart above, solve for OH^- and convert to pH.
For the sake of typing let's call the basic form of HEPES, BH2. In water solution this will ionize as
............BH2 + HOH ==> BH3^+ + OH^-
initial....0.1M.............0......0
change......-x.............x.......x
equil......0.1-x............x.......x
Kb = (BH3^+)(OH^-)/(BNH2)
Substitute from the ICE chart above, solve for OH^- and convert to pH.