If the same volume (130-mL) of the buffer were 0.265 M in NH3 and 0.400 M in NH4Br, what mass of HCl could be handled before the pH fell below 9.00?
I used the henderson-hasselbalch equation to solve this. i set it up as 9=9.24551+log((0.03445-x)/(0.052+x))
0.03445= moles of NH3
0.052= moles of NH4Br
I calculated the grams to be .11 g but it was wrong. Did i set up my H-H equation wrong?
1 answer
It appears to me that your set up is ok. But when I work the problem I don't get exactly 0.11 grams. More like 0.122 g. And if I divide 0.122/36.46 I get 0.00335 moles. And 9.25 + log[(34.45-3.35)/(52.0+3.35)] = 8.9997 which I rounded to 9.0. Actually, if you use 0.003348 it gives 9.0.