Which of the following combinations would be the best to buffer an aqueous solution at a pH of 5.0?
a.CH3CO2H and CH3COO-, Ka = 1.8 × 10^-5
b.H3PO4 and H2PO4-, Ka1 = 7.5 × 10^-3
c.H2PO4- and HPO42-, Ka2 = 6.2 × 10^-8
d.HNO2 and NO2-, Ka = 4.5 × 10^-4
e.NH4+ and NH3, Ka = 5.7 × 10^-10
2007-12-07 06:10:15 · 2 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
answer a since pKa is 4.74
so 5 =4.74+log [CH3COO-]/[CH3CO2H]
log [CH3COO-]/[CH3CO2H]=5-4.74=0.26
[CH3COO-]/[CH3CO2H]=10^0.26=1.82
easy to realize
2007-12-07 06:17:57 · answer #1 · answered by maussy 7 · 0⤊ 0⤋
Do the henderson hasselbach in case you won't be in a position to tell by potential of inspection. some could be eradicated certainly; think of roughly NH4+ , that is mildly acidic, and that is buffering area would be interior the 9's probably.
2016-12-17 10:30:27 · answer #2 · answered by ? 4 · 0⤊ 0⤋