Question

correct answer?

What information can be obtained from the Figure below? 14 12 10 pH 8 6 4 20 volume (mL) O The equivalence point occurs at pOH = 10 and the pKb = 6.0 O Both the pOH and the pKb cannot be calculated from the graph. The equivalence point occurs at pH = 8.0 and the pka = 4.0 O The equivalence point occurs at pH = 7.0 but the pka is not known from the graph.

Answer 1

The equivalence point is tue mid point of the curve when there is a sharp decrease in pH. It is about pH 4 and hence pOH =10, and the volume used for this is about 21ml. Half of its equivalent point is at a volume of nwarly 10.5 ml corresponding to pH 8. So pOH = 14-pH = 14-8=6. But at half of the equivalence point, pOH= pKb=6. Hence first option is correct i.e. pOH =10 at equivalence point(pH=4) and pkb =6