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Chapter 16: Problem 20
Fill in the word "acidic," "basic," or "neutral" for these solutions: (a) \(\mathrm{pOH}>7\); solution is _____. (b) \(\mathrm{pOH}=7\); solution is _____. (c) \(\mathrm{pOH}<7\); solution is _____.
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Predict whether a solution containing the salt \(\mathrm{K}_{2} \mathrm{HPO}_{4}\) will be acidic, neutral, or basic. (Hint: You need to consider both the ionization and hydrolysis of \(\mathrm{HPO}_{4}^{2-} .\)
What are the names and formulas of the conjugate bases of these acids: (a) \(\mathrm{HNO}_{2},\) (b) \(\mathrm{H}_{2} \mathrm{SO}_{4},\) (c) \(\mathrm{H}_{2} \mathrm{~S},\) (d) HCN, (e) HCOOH (formic acid)?
Hydrocyanic acid (HCN) is a weak acid and a deadly poisonous compound that, in the gaseous form (hydrogen cyanide), is used in gas chambers. Why is it dangerous to treat sodium cyanide with acids (such as HCl) without proper ventilation?
Identify the acid-base conjugate pairs in each of these reactions: (a) \(\mathrm{CH}_{3} \mathrm{COO}^{-}+\mathrm{HCN} \rightleftharpoons \mathrm{CH}_{3} \mathrm{COOH}+\mathrm{CN}^{-}\) (b) \(\mathrm{HCO}_{3}^{-}+\mathrm{HCO}_{3}^{-} \rightleftharpoons \mathrm{H}_{2} \mathrm{CO}_{3}+\mathrm{CO}_{3}^{2-}\) (c) \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}+\mathrm{NH}_{3} \rightleftharpoons \mathrm{HPO}_{4}^{2-}+\mathrm{NH}_{4}^{+}\) (d) \(\mathrm{HClO}+\mathrm{CH}_{3} \mathrm{NH}_{2} \rightleftharpoons \mathrm{CH}_{3} \mathrm{NH}_{3}^{+}+\mathrm{ClO}^{-}\) (e) \(\mathrm{CO}_{3}^{2-}+\mathrm{H}_{2} \mathrm{O} \rightleftharpoons \mathrm{HCO}_{3}^{-}+\mathrm{OH}^{-}\) (f) \(\mathrm{CH}_{3} \mathrm{COO}^{-}+\mathrm{H}_{2} \mathrm{O} \rightleftharpoons \mathrm{CH}_{3} \mathrm{COOH}+\mathrm{OH}^{-}\)
Teeth enamel is largely hydroxyapatite \(\left[\mathrm{Ca}_{5}\left(\mathrm{PO}_{4}\right)_{3} \mathrm{OH}\right]\). When it dissolves in water (a process called demineralization), it dissociates as follows: $$\mathrm{Ca}_{5}\left(\mathrm{PO}_{4}\right)_{3} \mathrm{OH} \longrightarrow 5 \mathrm{Ca}^{2+}+3 \mathrm{PO}_{4}^{3-}+\mathrm{OH}^{-}$$ The reverse process, called remineralization, is the body's natural defense against tooth decay. Acids produced from food remove the \(\mathrm{OH}^{-}\) ions and thereby weaken the enamel layer. Most toothpastes contain a flouride compound such as \(\mathrm{NaF}\) or \(\mathrm{SnF}_{2}\). What is the function of these compounds in preventing tooth decay?
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