Chapter 16

A $0.015-M$ solution of a monoprotic acid is 0.92 percent ionized. Calculate the ionization constant for the acid.

Calculate the concentration at which a monoprotic acid with $K_{\mathrm{a}}=4.5\times {10}^{-5}$ will be 2.5 percent ionized.

Calculate the $K_{\mathrm{a}}$ of a weak acid if a $0.19-M$ aqueous solution of the acid has a $\mathrm{pH}$ of 4.52 at ${25}^{\circ }\mathrm{C}$.

The $\mathrm{pH}$ of an aqueous acid solution is 6.20 at ${25}^{\circ }\mathrm{C}$. Calculate the $K_{\mathrm{a}}$ for the acid. The initial acid concentration is $0.010\mathrm{M}$.

What is the original molarity of a solution of formic acid $(\mathrm{HCOOH})$ whose $\mathrm{pH}$ is 3.26 at ${25}^{\circ }\mathrm{C}?(K_{\mathrm{a}}$ for $$\text{ formic acid }=1.7\times {10}^{-4}.)$$

What is the original molarity of a solution of a weak acid whose $K_{\mathrm{a}}$ is $3.5\times {10}^{-5}$ and whose $\mathrm{pH}$ is 5.26 at ${25}^{\circ }\mathrm{C}?$

Which of the following statements are true for a $0.10-M$ solution of a weak acid HA? (Choose all that apply.) (a) The pH is 1.00 . (c) $\left[{\mathrm{H}}_3{\mathrm{O}}^{+}\right]=\left[{\mathrm{A}}^{-}\right]$ (b) $\left[{\mathrm{H}}_3{\mathrm{O}}^{+}\right]>>\left[{\mathrm{A}}^{-}\right]$ (d) The $\mathrm{pH}$ is less than 1 .

Classify each of the following species as a weak or strong base: (a) $\mathrm{LiOH},(\mathrm{b}){\mathrm{CN}}^{-},(\mathrm{c}){\mathrm{H}}_2\mathrm{O},(\mathrm{d}){\mathrm{ClO}}_4^{-},(\mathrm{e}){\mathrm{NH}}_2^{-}$.

Compare the $\mathrm{pH}$ values for $0.10-\mathrm{M}$ solutions of $\mathrm{NaOH}$ and of ${\mathrm{NH}}_3$ to illustrate the difference between a strong base and a weak base.

Which of the following has a higher $\mathrm{pH}$ : (a) $1.0\mathrm{M}{\mathrm{NH}}_3$, (b) $0.20\mathrm{M}\mathrm{NaOH}(K_{\mathrm{b}}$ for ${\mathrm{NH}}_3=1.8\times {10}^{-5})$ ?