Chapter 15

How is a Brønsted-Lowry acid defined? How is a BrønstedLowry base defined? How do these definitions differ from the Arrhenius definition of acids and bases?

How are the formulas of the members of a conjugate acid-base pair related to each other? Within the pair, how can you tell which is the acid?

What is meant by the term amphoteric? Give two chemical equations that illustrate the amphoteric nature of water.

Define the term amphiprotic.

The position of equilibrium in the equation below lies far to the left. Identify the conjugate acid-base pairs. Which of the two acids is stronger? \(\mathrm{HOCl}(a q)+\mathrm{H}_{2} \mathrm{O} \rightleftharpoons \mathrm{H}_{3} \mathrm{O}^{+}(a q)+\mathrm{OCl}^{-}(a q)\)

Consider the following: \(\mathrm{CO}_{3}^{2-}\) is a weaker base than hydroxide ion, and \(\mathrm{HCO}_{3}^{-}\) is a stronger acid than water. In the equation below, would the position of equilibrium lie to the left or to the right? Justify your answer. \(\mathrm{CO}_{3}^{2-}(a q)+\mathrm{H}_{2} \mathrm{O} \rightleftharpoons \mathrm{HCO}_{3}^{-}(a q)+\mathrm{OH}^{-}(a q)\)

\(\mathrm{HClO}_{4}\) is a stronger proton donor than \(\mathrm{HNO}_{3}\), but in water both acids appear to be of equal strength; they are both \(100 \%\) ionized. Why is this so? What solvent property would be necessary in order to distinguish between the acidities of these two Brønsted-Lowry acids?

Within the periodic table, how do the strengths of the binary acids vary from left to right across a period? How do they vary from top to bottom within a group?

Explain why \(\mathrm{H}_{2} \mathrm{~S}\) is a stronger acid than \(\mathrm{H}_{2} \mathrm{O}\).

Explain why nitric acid is a stronger acid than nitrous acid. $$ \mathrm{HO}-\mathrm{NO}_{2} \quad \mathrm{HO}-\mathrm{NO} $$ nitric acid nitrous aci

Astatine, atomic number \(85,\) is radioactive and does not occur in appreciable amounts in nature. On the basis of what you have learned in this chapter, answer the following. (a) How would the acid strength of HAt compare with that of HI? (b) How would the acid strength of \(\mathrm{HAtO}_{3}\) compare with that of \(\mathrm{HBrO}_{3} ?\)

Explain why \(\mathrm{HClO}_{4}\) is a stronger acid than \(\mathrm{H}_{2} \mathrm{SeO}_{4}\)

Define Lewis acid and Lewis base.

Explain why the addition of a proton to a water molecule to give \(\mathrm{H}_{3} \mathrm{O}^{+}\) can be considered a Lewis acid-base reaction.

Methylamine has the formula \(\mathrm{CH}_{3} \mathrm{NH}_{2}\) and the structure Use Lewis structures to illustrate the reaction of methylamine with boron trifluoride.

Use Lewis structures to show the Lewis acid-base reaction between \(\mathrm{SO}_{3}\) and \(\mathrm{H}_{2} \mathrm{O}\) to give \(\mathrm{H}_{2} \mathrm{SO}_{4}\). Identify the Lewis acid and the Lewis base in the reaction.

Explain why the oxide ion, \(\mathrm{O}^{2-}\), can function as a Lewis base but not as a Lewis acid.

Suppose that a new element was discovered. Based on the discussions in this chapter, what properties (both physical and chemical) might be used to classify the element as a metal or a nonmetal?

If the oxide of an element dissolves in water to give an acidic solution, is the element more likely to be a metal or a nonmetal?

$$ \begin{aligned} &\text { Which ion is expected to give the more acidic solution, }\\\ &\mathrm{Fe}^{2+} \text { or } \mathrm{Fe}^{3+} \text { ? Why? } \end{aligned} $$

Ions of the alkali metals have little effect on the acidity of a solution. Why?

$$ \begin{aligned} &\text { What acid is formed when the following oxides react }\\\ &\text { with water? (a) } \mathrm{SO}_{3} \text { (b) } \mathrm{CO}_{2} \text { (c) } \mathrm{P}_{4} \mathrm{O}_{10} \end{aligned} $$

Write equations for the reaction of \(\mathrm{Al}_{2} \mathrm{O}_{3}\) with (a) a strong acid, and (b) a strong base.

What is a ceramic? How are ceramics formed from their raw materials?

What type of reaction is used in the sol-gel process? What small molecule is formed in the process for making the sol-gel suspension?

Write the formula for the conjugate acid of each of the following. (a) \(\mathrm{F}^{-}\) (b) \(\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{~N}\) (c) \(\mathrm{HCrO}_{4}^{-}\) (d) \(\mathrm{CN}^{-}\)

Write the formula for the conjugate acid of each of the following. (a) \(\mathrm{N}_{2} \mathrm{H}_{4}\) (b) \(\mathrm{O}^{2-}\) (c) \(\mathrm{SO}_{4}^{2-}\) (d) \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\)

Write the formula for the conjugate base of each of the following. (a) \(\mathrm{HSO}_{3}^{-}\) (b) \(\mathrm{H}_{5} \mathrm{IO}_{6}\) (c) \(\mathrm{HNO}_{3}\) (d) \(\mathrm{H}_{2} \mathrm{~S}\)

Identify the conjugate acid-base pairs in the following reactions. (a) \(\mathrm{HNO}_{3}+\mathrm{N}_{2} \mathrm{H}_{4} \rightleftharpoons \mathrm{NO}_{3}^{-}+\mathrm{N}_{2} \mathrm{H}_{5}^{+}\) (b) \(\mathrm{NH}_{3}+\mathrm{N}_{2} \mathrm{H}_{5}{\underline{\phantom{xx}}}^{+} \rightleftharpoons \mathrm{NH}_{4}^{+}+\mathrm{N}_{2} \mathrm{H}_{4}\) (c) \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}+\mathrm{CO}_{3}{\underline{\phantom{xx}}}^{2-} \rightleftharpoons \mathrm{HPO}_{4}^{2-}+\mathrm{HCO}_{3}^{-}\) (d) \(\mathrm{HIO}_{3}+\mathrm{HC}_{2} \mathrm{O}_{4}^{-} \rightleftharpoons \mathrm{IO}_{3}^{-}+\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\)

Identify the conjugate acid-base pairs in the following reactions. (a) \(\mathrm{HSO}_{4}^{-}+\mathrm{SO}_{3}^{2-} \rightleftharpoons \mathrm{HSO}_{3}^{-}+\mathrm{SO}_{4}^{2-}\) (b) \(\mathrm{S}^{2-}+\mathrm{H}_{2} \mathrm{O} \rightleftharpoons \mathrm{HS}^{-}+\mathrm{OH}^{-}\) (c) \(\mathrm{CN}^{-}+\mathrm{H}_{3} \mathrm{O}^{+} \rightleftharpoons \mathrm{HCN}+\mathrm{H}_{2} \mathrm{O}\) (d) \(\mathrm{H}_{2} \mathrm{Se}+\mathrm{H}_{2} \mathrm{O} \rightleftharpoons \mathrm{HSe}^{-}+\mathrm{H}_{3} \mathrm{O}^{+}\)

Choose the stronger acid: (a) \(\mathrm{HBr}\) or \(\mathrm{HCl}\), (b) \(\mathrm{H}_{2} \mathrm{O}\) or \(\mathrm{HF},\) (c) \(\mathrm{H}_{2} \mathrm{~S}\) or \(\mathrm{HBr}\). Give your reasons.

Choose the stronger acid: (a) \(\mathrm{H}_{2} \mathrm{~S}\) or \(\mathrm{H}_{2} \mathrm{Se},\) (b) \(\mathrm{H}_{2} \mathrm{Te}\) or \(\mathrm{HI},\) (c) \(\mathrm{PH}_{3}\) or \(\mathrm{NH}_{3}\). Give your reasons.

Choose the stronger acid and give your reason: (a) HOCl or \(\mathrm{HClO}_{2}\), (b) \(\mathrm{H}_{2} \mathrm{SeO}_{4}\) or \(\mathrm{H}_{2} \mathrm{SeO}_{3}\)

$$ \begin{aligned} &\text { Choose the stronger acid and give your reason: }\\\ &\text { (a) } \mathrm{HIO}_{3}\\\ &\text { or } \mathrm{HIO}_{4} \text { , (b) } \mathrm{H}_{3} \mathrm{AsO}_{4} \text { or } \mathrm{H}_{3} \mathrm{As} \mathrm{O}_{3} \text { . } \end{aligned} $$

Use Lewis symbols to diagram the reaction $$ \mathrm{NH}_{2}^{-}+\mathrm{H}^{+} \longrightarrow \mathrm{NH}_{3} $$ Identify the Lewis acid and Lewis base in the reaction.

Use Lewis symbols to diagram the reaction $$ \mathrm{BF}_{3}+\mathrm{F}^{-} \longrightarrow \mathrm{BF}_{4} $$

Aluminum chloride, \(\mathrm{AlCl}_{3}\), forms molecules with itself with the formula \(\mathrm{Al}_{2} \mathrm{Cl}_{6}\). Its structure is Use Lewis structures to show how the reaction \(2 \mathrm{AlCl}_{3} \longrightarrow\) \(\mathrm{Al}_{2} \mathrm{Cl}_{6}\) is a Lewis acid-base reaction.

Use Lewis structures to diagram the reaction $$ \mathrm{CO}_{2}+\mathrm{O}^{2-} \longrightarrow \mathrm{CO}_{3}^{2-} $$ Identify the Lewis acid and Lewis base in the reaction.

Use Lewis structures to show how the following reaction involves the transfer of a Lewis base from one Lewis acid to another. Identify the Lewis acid and Lewis base. $$ \mathrm{CO}_{3}^{2-}+\mathrm{SO}_{2} \longrightarrow \mathrm{CO}_{2}+\mathrm{SO}_{3}^{2-} $$

Use Lewis structures to show how the following reaction can be viewed as the displacement of one Lewis base by another Lewis base from a Lewis acid. Identify the two Lewis bases and the Lewis acid. $$ \mathrm{NH}_{2}^{-}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{NH}_{3}+\mathrm{OH}^{-} $$

The ion \(\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}^{3+}\) is weakly acidic. Write an equation showing its behavior as a Brønsted-Lowry acid in water.

The ion \(\mathrm{Hg}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}^{2+}\) acts as an acid. Write an equation showing its behavior as a Brønsted-Lowry acid in water.

Explain why \(\mathrm{CaO}\) is an anhydrous base and \(\mathrm{SO}_{2}\) is an anhydrous acid.

Using liquid ammonia as a solvent, sodium amide reacts with ammonium chloride in an acid-base neutralization reaction. Assuming that these compounds are completely dissociated in liquid ammonia, write molecular, ionic, and net ionic equations for the reaction. Which substance is the acid and which is the base?

Write equations that illustrate the amphiprotic nature of the bicarbonate ion.

Sodium hydroxide, \(\quad \mathrm{NaOH},\) is basic. Aluminum hydroxide, \(\mathrm{Al}\left(\mathrm{H}_{2} \mathrm{O}\right)_{3}(\mathrm{OH})_{3},\) is amphoteric. The compound \(\mathrm{O}_{3} \mathrm{ClOH}\) (usually written \(\mathrm{HClO}_{4}\) ) is acidic. Considering that each compound contains one or more OH groups, why are their acid-base properties so different?

Hydrazine, \(\mathrm{N}_{2} \mathrm{H}_{4}\), is a weaker Brønsted-Lowry base than ammonia. In the following reaction, would the position of equilibrium lie to the left or to the right? Justify your answer $$ \mathrm{N}_{2} \mathrm{H}_{5}^{+}+\mathrm{NH}_{3} \rightleftharpoons \mathrm{N}_{2} \mathrm{H}_{4}+\mathrm{NH}_{4}^{+} $$

Identify the two Brønsted-Lowry acids and two bases in the reaction $$ \mathrm{NH}_{2} \mathrm{OH}+\mathrm{CH}_{3} \mathrm{~N}^{+} \rightleftharpoons \mathrm{NH}_{3} \mathrm{OH}^{+}+\mathrm{CH}_{3} \mathrm{NH}_{2} $$