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Chapter 16: Problem 84

Predict whether aqueous solutions of the following substances are acidic, basic, or neutral: (a) \(\mathrm{AlCl}_{3},(\mathbf{b}) \mathrm{NaBr},\) (c) $\mathrm{NaClO},(\mathbf{d})\left[\mathrm{CH}_{3} \mathrm{NH}_{3}\right] \mathrm{NO}_{3},$ (e) \(\mathrm{Na}_{2} \mathrm{SO}_{3}\)

Short Answer

Expert verified
(a) The aqueous solution of AlCl3 will be acidic. (b) The aqueous solution of NaBr is neutral. (c) The aqueous solution of NaClO is basic. (d) The aqueous solution of \(\left[\mathrm{CH}_{3} \mathrm{NH}_{3}\right]\mathrm{NO}_{3}\) will be acidic. (e) The aqueous solution of \(\mathrm{Na}_{2} \mathrm{SO}_{3}\) is basic.

Step by step solution

01

(a) Analyzing AlCl3

Aluminum chloride, \(\mathrm{AlCl}_{3}\), forms an Al\(^{3+}\) ion and three Cl\(^-\) ions when dissolved in water. The Al\(^{3+}\) ion is a Lewis acid, and it will react with water molecules to form Al(H\(_2\)O)\(_3^{3+}\) and release H\(^+\) ions into the solution, increasing the acidity. The Cl\(^-\) ions are mostly spectator ions that do not affect acidity/basicity. Therefore, an aqueous solution of AlCl3 will be acidic.
02

(b) Analyzing NaBr

Sodium bromide, NaBr, forms a Na\(^+\) ion and a Br\(^-\) ion when dissolved in water. The Na\(^+\) ions are spectactor ions that do not affect acidity/basicity. The Br\(^-\) ion is a conjugate base of a strong acid, HBr, and it will not hydrolyze to form a significant amount of hydroxide ions. Therefore, the aqueous solution of sodium bromide is neutral.
03

(c) Analyzing NaClO

Sodium hypochlorite, NaClO, forms a Na\(^{+}\) ion and a ClO\(^{-}\) ion when dissolved in water. The Na\(^{+}\) ions are spectator ions and do not affect acidity/basicity. The ClO\(^-\) ion is a conjugate base of a weak acid, HOCl, so it will hydrolyze to produce OH\(^{-}\) ions in solution. Therefore, the aqueous solution of sodium hypochlorite is basic.
04

(d) Analyzing CH3NH3NO3

Methylammonium nitrate, \(\left[\mathrm{CH}_{3} \mathrm{NH}_{3}\right]\mathrm{NO}_{3}\), forms a CH\(_3\)NH\(_3^{+}\) ion and a NO\(_3^-\) ion when dissolved in water. The CH\(_3\)NH\(_3^{+}\) ion is a conjugate acid of a weak base, CH\(_3\)NH\(_2\), and it will release H\(^+\) ions in solution. The NO\(_3^-\) ion is a conjugate base of a strong acid, HNO\(_3\), and it will not hydrolyze to form a significant amount of hydroxide ions. Thus, the aqueous solution of methylammonium nitrate will be acidic.
05

(e) Analyzing Na2SO3

Sodium sulfite, \(\mathrm{Na}_{2} \mathrm{SO}_{3}\), forms two Na\(^+\) ions and one SO\(_3^{2-}\) ion when dissolved in water. The Na\(^+\) ions are spectator ions that do not affect acidity/basicity. The SO\(_3^{2-}\) ion is a conjugate base of a weak acid, HSO\(_3^-\), and it will hydrolyze to produce OH\(^{-}\) ions in solution. Therefore, the aqueous solution of sodium sulfite is basic.

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Most popular questions from this chapter

An unknown salt is either $\mathrm{KBr}, \mathrm{NH}_{4} \mathrm{Cl}, \mathrm{KCN},\( or \)\mathrm{K}_{2} \mathrm{CO}_{3} .\( If a \)0.100 \mathrm{M}$ solution of the salt is neutral, what is the identity of the salt?

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 \(\left(\mathrm{Mg}\left(\mathrm{NO}_{2}\right)_{2}\right)\).

Atmospheric \(\mathrm{CO}_{2}\) levels have risen by nearly \(20 \%\) over the past 40 years from 320 ppm to 400 ppm. (a) Given that the average \(\mathrm{pH}\) of clean, unpolluted rain today is 5.4 , determine the \(\mathrm{pH}\) of unpolluted rain 40 years ago. Assume that carbonic acid \(\left(\mathrm{H}_{2} \mathrm{CO}_{3}\right)\) formed by the reaction of \(\mathrm{CO}_{2}\) and water is the only factor influencing \(\mathrm{pH}\). $$ \mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftharpoons \mathrm{H}_{2} \mathrm{CO}_{3}(a q) $$ (b) What volume of \(\mathrm{CO}_{2}\) at \(25^{\circ} \mathrm{C}\) and \(101.3 \mathrm{kPa}\) is dissolved in a 20.0-L bucket of today's rainwater?

Calculate the molar concentration of \(\mathrm{OH}^{-}\) in a \(0.724 \mathrm{M}\) solution of hypobromite ion $\left(\mathrm{BrO}^{-} ; K_{b}=4.0 \times 10^{-6}\right) .\( What is the \)\mathrm{pH}$ of this solution?

Indicate whether each of the following statements is true or false. For each statement that is false, correct the statement to make it true. (a) Acid strength in a series of \(\mathrm{H}-\mathrm{A}\) molecules increases with increasing size of A. (b) For acids of the same general structure but differing electronegativities of the central atoms, acid strength decreases with increasing electronegativity of the central atom. (c) The strongest acid known is HF because fluorine is the most electronegative element.
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