How do you calculate the number of moles of NaOH to add to a liter of 1M NH4CL (pka of NH4+ = 9.25 ) to produce a solution buffering the pH at 8.75 ? thanks
2 answers
NiOOH
The Henderson-Hasselbalch equation is
pH = pKa + log[(base)/(acid)]
8.75 = 9.25 + log (B)/(1-B)
Solve for (base). I get approximately .25 but you need to go through it more accurately. THEN, I always like to check it to make sure I get a pH of 8.75.
Using the approximate numbers,
NH4^+ + OH^- ==> NH3 + H2O
1mole....0.........0
add......B.........
1-B......0..........B
If b = 0.25, then 1-B = 0.75 and
pH = 9.25 + log(0.25/0.75)
pH = 8.77. This will be 8.75 when you do it more accurately.
pH = pKa + log[(base)/(acid)]
8.75 = 9.25 + log (B)/(1-B)
Solve for (base). I get approximately .25 but you need to go through it more accurately. THEN, I always like to check it to make sure I get a pH of 8.75.
Using the approximate numbers,
NH4^+ + OH^- ==> NH3 + H2O
1mole....0.........0
add......B.........
1-B......0..........B
If b = 0.25, then 1-B = 0.75 and
pH = 9.25 + log(0.25/0.75)
pH = 8.77. This will be 8.75 when you do it more accurately.
2 answers