A dibasic compound, B, has pKb1 5 4.00 and pKb2 5 6.00.

Find the fraction in the form BH22+at pH 7.00, using Equation

10-19. Note that K1 and K2 in Equation 10-19 are acid dissociation

constants forlocalid="1655450143786" BH22+

1 (K1 = Kw/Kb2 and K2 = Kw/Kb1).

Short Answer

Expert verified

The answer isa(BH22+)=0.91.

Step by step solution

01

Dibasic acid

Dibasic, or diprotic acid, an acid containing two potential protons to donate. Dibasic salt, is a salt with two hydrogen atoms, with respect to the parent acid, replaced by cations. Dibasic ester, is an ester of a dicarboxylic acid.

02

Calculating fraction in the form   at pH 7.00

We will use the following:

[H+]=10-7from pH=7.00

K1=10-8from pKb2=6.00

K2=10-10from pb1=4.00

In order to find the fraction in the form of BH22+,

a(BH22)=[H+][H+]2+[H+]K1+K1K2a(BH22)=(10-7)2(10-7)2+(10-7)×(10-8)+(10-8×10-10)a(BH22)=0.91

The final answer is;a(BH22)=0.91

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Most popular questions from this chapter

  1. Fractional composition in a tetraprotic system. Prepare a fractional composition diagram analogous to Figure 10-4 for the tetraprotic system derived from hydrolysis of Cr+:

localid="1654853037629" Cr3++H2OCrOH2++H+Ka1=10-3.80CrOH2++H2OCrOH2++H+Ka2=10-6.40CrOH2++H2OCrOH3aq+H+Ka3=10-6.40CrOH3aq+H2OCrOH4-+H+Ka4=-11.40

(Yes, the values oflocalid="1654853051658" Ka2andlocalid="1654853058271" Ka3are equal.)

(a) Use these equilibrium constants to prepare a fractional composition diagram for this tetraprotic system.

(b) You should do this part with your head and your calculator, not your spreadsheet. The solubility of is given by

localid="1654853063951" CrOH3SCrOH3aqKa3=10-6.80

What concentration of localid="1654853075036" CrOH3aqis in equilibrium with solid localid="1654853085944" CrOH3aqS?

(c) What concentration oflocalid="1654853094735" CrOH2+is in equilibrium with localid="1654853101499" CrOH3aqSif the solution localid="1654853109266" pHis adjusted tolocalid="1654853117749" 4.00?

The acid HA has pKa= 4.00. Find the fraction in the form HA and the fraction in the form A- at pH = 5.00. Does your answer agree with what you

expect for the quotient [A2]/[HA] at pH 5.00?

Consider HA-, the intermediate form of a diprotic acid.K2for this species is10-4andKbis10-8. Nonetheless, the Kaand Kbreactions proceed to nearly the same extent when NaHA is dissolved in water. Explain.

Create a spreadsheet with Equations 10-19 through 10-21 to compute the three curves in Figure 10-4. Plot the three curves in a beautifully labeled figure.

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