How many grams of solid ammonium bromide should be added to 1.00 L of a 0.293 M ammonia solution to prepare a buffer with a pH of 8.610 ?
grams ammonium bromide = g.
mixture of NH3 and NH4Br act as basic buffer
pOH = pKb + log [NH4Br] / [NH3]
pH =8.610
pOH = 14 - 8.610 = 5.390
pKb of NH3 = 4.74
5.390 = 4.74 + log [NH4Br] /[0.293]
0.65 = log [NH4Br] - log [0.293]
0.65 = log [NH4Br] + 0.53
log [NH4Br] = 0.15
[NH4Br] = 1.32 M
now
Molarity = (W /MW) (1 /V in L)
1.32 = (W / 97.94)(1/1)
W = 129.3 g
mass of NH4Br required = 129.3 g
How many grams of solid ammonium bromide should be added to 1.00 L of a 0.293...