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Chapter 16: Problem 89

Based on their compositions and structures and on conjugate acid-base relationships, select the stronger base in each of the following pairs: (a) \(\mathrm{BrO}^{-}\) or \(\mathrm{ClO}^{-},(\mathbf{b}) \mathrm{BrO}^{-}\) or \(\mathrm{BrO}_{2}^{-}\), (c) \(\mathrm{HPO}_{4}^{2-}\) or $\mathrm{H}_{2} \mathrm{PO}_{4}^{-}$.

Short Answer

Expert verified
The stronger bases in each pair are: (a) \(\mathrm{BrO}^{-}\), (b) \(\mathrm{BrO}^{-}\), and (c) \(\mathrm{HPO}_{4}^{2-}\).

Step by step solution

01

(a) Comparing Basicity of \(\mathrm{BrO}^{-}\) and \(\mathrm{ClO}^{-}\)

In this pair, both ions are from the same group (Group 17), but \(\mathrm{BrO}^{-}\) has bromine and \(\mathrm{ClO}^{-}\) has chlorine. Chlorine is more electronegative than bromine, which means it has a stronger ability to stabilize a negative charge on its conjugate acid. Therefore, the conjugate acid of \(\mathrm{ClO}^{-}\) is more stable, and \(\boldsymbol{\mathrm{BrO}^{-}}\) is the stronger base.
02

(b) Comparing Basicity of \(\mathrm{BrO}^{-}\) and \(\mathrm{BrO}_{2}^{-}\)

Both of these ions contain bromine, but \(\mathrm{BrO}^{-}\) has one oxygen atom while \(\mathrm{BrO}_{2}^{-}\) has two. \(\mathrm{BrO}_{2}^{-}\) has more resonance structures that can distribute the negative charge among the multiple oxygen atoms, making its conjugate acid more stable. This leads to the conclusion that \(\boldsymbol{\mathrm{BrO}^{-}}\) is the stronger base in this pair as well.
03

(c) Comparing Basicity of \(\mathrm{HPO}_{4}^{2-}\) and \(\mathrm{H}_{2}\mathrm{PO}_{4}^{-}\)

In this pair, \(\mathrm{HPO}_{4}^{2-}\) has one hydrogen atom while \(\mathrm{H}_{2}\mathrm{PO}_{4}^{-}\) has two. When comparing the conjugate acids of these two, the \(\mathrm{H}_{2}\mathrm{PO}_{4}^{-}\) ion would lose a hydrogen to become \(\mathrm{H_{3}PO_{4}}\), while \(\mathrm{HPO}_{4}^{2-}\) would gain a hydrogen to become \(\mathrm{H_{2}PO_{4}^{-}\). Since \(\mathrm{H_{3}PO_{4}}\) is more acidic than \(\mathrm{H_{2}PO_{4}^{-}\), it means that the conjugate base \(\mathrm{H_{2}PO_{4}^{-}}\) is weaker than the conjugate base \(\mathrm{HPO}_{4}^{2-}\). Thus, \(\boldsymbol{\mathrm{HPO}_{4}^{2-}}\) is the stronger base in this pair.

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Most popular questions from this chapter

Write the chemical equation and the \(K_{b}\) expression for the reaction of each of the following bases with water: (a) trimethylamine, \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N} ;\) (b) sulfite, \(\mathrm{SO}_{3}^{2-}\); (c) cyanide, \(\mathrm{CN}^{-}\).

(a) Given that \(K_{a}\) for cyanic acid is \(3.5 \times 10^{-4}\) and that for hydrofluoric acid is \(6.8 \times 10^{-4},\) which is the stronger acid? (b) Which is the stronger base, the cyanate ion or the fluoride ion? (c) Calculate \(K_{b}\) values for \(\mathrm{NCO}^{-}\) and \(\mathrm{F}^{-}\).

Calculate the number of \(\mathrm{H}^{+}(a q)\) ions in \(1.0 \mathrm{~mL}\) of pure water at \(25^{\circ} \mathrm{C}\).

Calculate the \(\mathrm{pH}\) of each of the following strong acid solutions: (a) \(8.3 \times 10^{-4} \mathrm{MHCl},(\mathbf{b}) 1.20 \mathrm{~g}\) of \(\mathrm{HNO}_{3}\) in \(500 \mathrm{~mL}\) of solution, $(\mathbf{c}) 2.0 \mathrm{~mL}\( of \)0.250 \mathrm{M} \mathrm{HClO}_{4}\( diluted to \)40.0 \mathrm{~mL}\(, (d) a solution formed by mixing \)25.0 \mathrm{~mL}\( of \)0.100 \mathrm{M} \mathrm{HBr}\( with \)25.0 \mathrm{~mL}\( of \)0.200 \mathrm{M} \mathrm{HCl}$.

Using data from Appendix \(D\), calculate \(p O H\) and \(p H\) for each (a) \(0.080 M\) potassium hypobromite of the following solutions: \((\mathrm{KBrO}),\) (b) \(0.150 \mathrm{M}\) potassium hydrosulfide \((\mathrm{KHS}),(\mathbf{c})\) a mixture that is \(0.25 \mathrm{M}\) in potassium nitrite \(\left(\mathrm{KNO}_{2}\right)\) and \(0.15 \mathrm{M}\) in magnesium nitrite \(\left(\mathrm{Mg}\left(\mathrm{NO}_{2}\right)_{2}\right)\).
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