Question
A buffer system contains 0.25M NH4+ and 0.19M NH3. pka of NH4 is 9.25.
How many moles of NaOH must be added to 1.00L of this solution to increase the pH to 9.25?
How many moles of NaOH must be added to 1.00L of this solution to increase the pH to 9.25?
Answers
DrBob222
mol NH3 = M x L = 0.19*1 = 0.190
mol NH4^+ = 0.25*1 = 0.250
-----------------
........NH4^+ + OH^- ==> NH3 + H2O
I.....0.250.....0......0.190
add..............x............
C.......-x......-x.......+x
E.....0.250-x.....0......0.190+x
Substitute into the Henderson-Hasselbalch equation and solve for x = mol NaOH added to 1L buffer to make pH = 9.25
mol NH4^+ = 0.25*1 = 0.250
-----------------
........NH4^+ + OH^- ==> NH3 + H2O
I.....0.250.....0......0.190
add..............x............
C.......-x......-x.......+x
E.....0.250-x.....0......0.190+x
Substitute into the Henderson-Hasselbalch equation and solve for x = mol NaOH added to 1L buffer to make pH = 9.25