/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 130 Are solutions of the following s... [FREE SOLUTION] | 91影视

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Chapter 14: Problem 130

Are solutions of the following salts acidic, basic, or neutral? For those that are not neutral, write balanced equations for the reactions causing the solution to be acidic or basic. The relevant \(K_{\mathrm{a}}\) and \(K_{\mathrm{b}}\) values are found in Tables 14.2 and \(14.3 .\) \(\begin{array}{ll}{\text { a. } \operatorname{Sr}\left(\mathrm{NO}_{3}\right)_{2}} & {\text { d. } \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{3} \mathrm{ClO}_{2}} \\ {\text { b. } \mathrm{NH}_{4} \mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}} & {\text { e. } \mathrm{NH}_{4} \mathrm{F}} \\ {\text { c. } \mathrm{CH}_{3} \mathrm{NH}_{3} \mathrm{O} \mathrm{l}} & {\text { f. } \mathrm{CH}_{3} \mathrm{NH}_{3} \mathrm{CN}}\end{array}\)

Short Answer

Expert verified
The solutions are: a. Sr(NO鈧�)鈧�: neutral b. NH鈧凜鈧侶鈧僌鈧�: relatively neutral c. CH鈧僋H鈧僌l: acidic (CH鈧僋H鈧� + H鈧僌l鈦�) d. C鈧咹鈧匩H鈧僀lO鈧�: acidic e. NH鈧凢: basic (NH鈧� + HF) f. CH鈧僋H鈧僀N: relatively neutral

Step by step solution

01

Identify the ions in the salts and classify as acidic, basic, or neutral

First, let's identify the ions present in each salt and classify them depending on their acidic, basic, or neutral properties. a. Sr(NO3)鈧�: Sr虏鈦� (neutral), NO鈧冣伝 (neutral) b. NH鈧凜鈧侶鈧僌鈧�: NH鈧勨伜 (acidic), C鈧侶鈧僌鈧傗伝 (basic) c. CH鈧僋H鈧僌l: CH鈧僋H鈧冣伜 (acidic), Ol鈦� (neutral) d. C鈧咹鈧匩H鈧僀lO鈧�: C鈧咹鈧匩H鈧冣伜 (acidic), ClO鈧傗伝 (neutral) e. NH鈧凢: NH鈧勨伜 (acidic), F鈦� (basic) f. CH鈧僋H鈧僀N: CH鈧僋H鈧冣伜 (acidic), CN鈦� (basic)
02

Determine the nature of the solutions using \(K_a\) and \(K_b\) values

We'll now determine the nature of the solutions based on the ions' conjugate acids and bases, and their \(K_a\) and \(K_b\) values. If the ion is derived from a weak acid or base, its conjugate should be stronger, making the solution acidic or basic. a. Sr(NO鈧�)鈧�: Since both ions are neutral, the solution is neutral. b. NH鈧凜鈧侶鈧僌鈧�: Acidic and basic ions are both present, so we need to compare their strengths. NH鈧勨伜 (conjugate acid of NH鈧�, a weak base) and C鈧侶鈧僌鈧傗伝 (conjugate base of acetic acid, a weak acid). Since their strengths are comparable, the solution should be relatively neutral. c. CH鈧僋H鈧僌l: Since CH鈧僋H鈧冣伜 is acidic and Ol鈦� is neutral, the solution is acidic. d. C鈧咹鈧匩H鈧僀lO鈧�: C鈧咹鈧匩H鈧冣伜 is acidic, and ClO鈧傗伝 is neutral, the solution is acidic. e. NH鈧凢: Both NH鈧勨伜 and F鈦� are present, so we need to compare their strengths. NH鈧勨伜 is acidic, and F鈦� is the conjugate base of HF, a weak acid, so the basic ion is stronger, and the solution is basic. f. CH鈧僋H鈧僀N: Both CH鈧僋H鈧冣伜 and CN鈦� are present; we need to compare their strengths. Since CN鈦� is the conjugate base of HCN, a weak acid, and CH鈧僋H鈧冣伜 is the conjugate acid of CH鈧僋H鈧�, a weak base, the solution should be relatively neutral.
03

Write balanced equations for the acidic or basic reactions

c. CH鈧僋H鈧僌l 鈫� CH鈧僋H鈧� + H鈧僌l鈦� e. NH鈧凢 鈫� NH鈧� + HF In summary, we have the following solutions: a. Sr(NO鈧�)鈧�: neutral b. NH鈧凜鈧侶鈧僌鈧�: relatively neutral c. CH鈧僋H鈧僌l: acidic d. C鈧咹鈧匩H鈧僀lO鈧�: acidic e. NH鈧凢: basic f. CH鈧僋H鈧僀N: relatively neutral

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Salts
Salts are ionic compounds made up of a cation (positive ion) and an anion (negative ion). They are commonly formed from the neutralization reaction between an acid and a base. When dissolved in water, salts can affect the pH of the solution depending on the nature of the ions they release.

In a neutralization reaction, the hydrogen ions (\(H^+\)) from the acid and the hydroxide ions (\(OH^-\)) from the base combine to form water. The remaining ions form the salt. For instance, NaCl is formed when hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH). However, not all salts are neutral. Some salts can make solutions acidic or basic due to the presence of conjugate acids or bases that alter the pH.

Understanding the behavior of salts in water involves recognizing the ions they dissociate into and determining whether these ions undergo further reactions with water that can affect the pH. This reaction is key to identifying whether a solution of salt will be acidic, basic, or neutral.
  • If a salt formed from a strong acid and a strong base, the resulting solution is neutral.
  • If a salt comes from a strong base and a weak acid, the solution tends to be basic.
  • If it originates from a weak base and a strong acid, the solution is often acidic.
Conjugate Acids and Bases
In the context of acid-base equilibria, conjugate acids and bases are fundamental to understanding how solutions can be acidic or basic. When an acid donates a proton (\(H^+\)), it forms its conjugate base. Conversely, when a base accepts a proton, it forms its conjugate acid.

For example, consider the dissociation of acetic acid (\(CH_3COOH\)): when it donates a proton, it forms acetate (\(CH_3COO^-\)), which is its conjugate base. Similarly, ammonia (\(NH_3\)), when accepting a proton, becomes ammonium (\(NH_4^+\)), its conjugate acid.

Why is the concept of conjugate pairs important? It's because they help determine the pH of salt solutions.
  • If a conjugate base of a weak acid is present in a salt, it can react with water to form hydroxide ions (\(OH^-\)), making the solution basic.
  • On the other hand, the conjugate acid of a weak base can react with water to form hydronium ions (\(H_3O^+\)), making the solution acidic.
Understanding which ion acts as a conjugate acid or base allows us to predict the behavior of the solution once the salt dissolves in water.
pH of Solutions
The pH of a solution is a measure of its acidity or basicity. It is calculated based on the concentration of hydrogen ions (\([H^+]\)) in the solution. The pH scale ranges from 0 to 14 with 7 being neutral. Values below 7 indicate an acidic solution, and values above 7 indicate a basic solution.

When a salt dissolves in water, the ions that compose the salt may interact with water to release or absorb hydrogen ions, thus altering the pH.
  • A solution is acidic if it increases the \([H^+]\) concentration, lowering the pH.
  • A solution is basic if it decreases the \([H^+]\) concentration, raising the pH.

For example, ammonium fluoride (NH鈧凢) dissolves to provide NH鈧勨伜 and F鈦� ions. NH鈧勨伜 can release an \(H^+\) ion, while F鈦� tends to keep the solution basic due to its origin from hydrofluoric acid (HF), a weak acid.

Calculating pH often involves the dissociation constants of the weak acid or base from which the conjugate emerges. Using the \(K_a\) (acid dissociation constant) and \(K_b\) (base dissociation constant) values helps in estimating whether the added ions will push the solution towards acidity or basicity. By comparing these values, you can predict whether the salt solution will behave more like an acid or a base.

The key takeaway? Knowing the nature of the ions in a salt and their dissociation constants helps us estimate the resulting pH once the salt is in a solution.

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Most popular questions from this chapter

Acrylic acid \(\left(\mathrm{CH}_{2}=\mathrm{CHCO}_{2} \mathrm{H}\right)\) is a precursor for many important plastics. \(K_{\mathrm{a}}\) for acrylic acid is \(5.6 \times 10^{-5} .\) a. Calculate the pH of a \(0.10-M\) solution of acrylic acid. b. Calculate the percent dissociation of a \(0.10-M\) solution of acrylic acid. c. calculate the pH of a \(0.050-M\) solution of sodium acrylate \(\left(\mathrm{NaC}_{3} \mathrm{H}_{3} \mathrm{O}_{2}\right)\)

Trichloroacetic acid \(\left(\mathrm{CCl}_{3} \mathrm{CO}_{2} \mathrm{H}\right)\) is a corrosive acid that is used to precipitate proteins. The pH of a \(0.050-M\) solution of trichloroacetic acid is the same as the pH of a \(0.040-M \mathrm{HClO}_{4}\) solution. Calculate \(K_{\mathrm{a}}\) for trichloroacetic acid.

Papaverine hydrochloride (abbreviated papH \(^{+} \mathrm{Cl}^{-} ;\) molar mass \(=378.85 \mathrm{g} / \mathrm{mol}\) ) is a drug that belongs to a group of medicines called vasodilators, which cause blood vessels to expand, thereby increasing blood flow. This drug is the conjugate acid of the weak base papaverine (abbreviated pap; \(K_{\mathrm{b}}=\) \(8.33 \times 10^{-9}\) at \(35.0^{\circ} \mathrm{C} ) .\) Calculate the \(\mathrm{pH}\) of a \(30.0-\mathrm{mg} / \mathrm{mL}\) aqueous dose of papH \(^{+} \mathrm{Cl}^{-}\) prepared at \(35.0^{\circ} \mathrm{C} . K_{\mathrm{w}}\) at \(35.0^{\circ} \mathrm{C}\) is \(2.1 \times 10^{-14} .\)

Zinc hydroxide is an amphoteric substance. Write equations that describe \(\mathrm{Zn}(\mathrm{OH})_{2}\) acting as a Bronsted-Lowry base toward \(\mathrm{H}^{+}\) and as a Lewis acid toward \(\mathrm{OH}^{-} .\)

The pH of human blood is steady at a value of approximately 7.4 owing to the following equilibrium reactions: $$ \mathrm{CO}_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftharpoons \mathrm{H}_{2} \mathrm{CO}_{3}(a q) \rightleftharpoons \mathrm{HCO}_{3}^{-}(a q)+\mathrm{H}^{+}(a q) $$ Acids formed during normal cellular respiration react with the \(\mathrm{HCO}_{3}^{-}\) to form carbonic acid, which is in equilibrium with \(\mathrm{CO}_{2}(a q)\) and \(\mathrm{H}_{2} \mathrm{O}(l) .\) During vigorous exercise, a person's \(\mathrm{H}_{2} \mathrm{CO}_{3}\) blood levels were \(26.3 \mathrm{mM},\) whereas his \(\mathrm{CO}_{2}\) levels were 1.63 \(\mathrm{mM}\) . On resting, the \(\mathrm{H}_{2} \mathrm{CO}_{3}\) levels declined to 24.9 \(\mathrm{m} M\) . What was the \(\mathrm{CO}_{2}\) blood level at rest?
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