91Ó°ÊÓ

Acrylic acid, \(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{COOH}\), is a weak monoprotic acid. Write a balanced equation for the reaction that occurs when \(25.0 \mathrm{~mL}\) of \(0.200 \mathrm{M} \mathrm{KOH}\) is added to \(50.0 \mathrm{~mL}\) of \(0.200 \mathrm{M} \mathrm{C}_{2} \mathrm{H}_{3} \mathrm{COOH}\). Besides water, what species are present in the solution? Is this solution a buffer? Why or why not?

How many grams of \(\mathrm{LiOH}\) are there in \(750 \mathrm{~mL}\) of an aqueous LiOH solution having an \(\mathrm{H}_{3} \mathrm{O}^{+}\) concentration of \(2.30 \times 10^{-13} \mathrm{M} ?\)

What is the molar hydroxide ion concentration in a solution that is 1000 times more acidic than a solution that has a pH of \(9.20\) ?

Classify each substance as strong electrolyte, weak electrolyte, or nonelectrolyte: (a) \(\mathrm{CH}_{3} \mathrm{COOH}\) (b) \(\mathrm{KCH}_{3} \mathrm{COO}\) (c) \(\mathrm{H}_{2} \mathrm{SO}_{4}\) (d) \(\mathrm{CH}_{2} \mathrm{Cl}_{2}\) (e) \(\mathrm{NH}_{3}\) (f) \(\mathrm{H}_{3} \mathrm{PO}_{4}\) (g) \(\mathrm{ZnSO}_{4}\)

Lithium hydride (LiH) is a source of hydride ion, shown below. \(\mathrm{H}\) : As you can see, the hydride ion has a negative charge (it is an anion) and a lone pair of electrons. When thrown into water, the hydride ion makes the water strongly basic. Write a reaction that shows how the hydride ion reacts with water to make the water basic. Then explain in English what the hydride ion does to water molecules to make the resulting solution basic.

Complete the following sentence: "The lower the \(\mathrm{p} K_{\mathrm{a}}\), the (stronger/weaker) the acid." \(^{\prime \prime}\) How does this parallel pH?

Glycine is the simplest of amino acids and is shown below. the amino acid glycine Notice that it has a weak COOH end similar to acetic acid. Like acetic acid, this end is weakly acidic. It also has an \(\mathrm{NH}_{2}\) end similar to \(\mathrm{NH}_{3}\). Like \(\mathrm{NH}_{3}\), this end is weakly basic. Although not technically a buffer, when glycine is added to water, the solution is buffered against addition of strong acid or base. Explain why.

Actually, once in water, the amino acid glycine (see problem above) exists as a zwitterion, as shown below. A zwitterion is an overall electrically neutral species that nevertheless has \(\mathrm{a}+\) and \(-\) charge in it. Zwitterionic form of glycine Now, the \(\mathrm{NH}_{3}{ }^{+}\) end is weakly acidic and the \(\mathrm{COO}^{-}\) end is weakly basic. Does this mean that the zwitterionic form cannot supply buffering action against strong acid or strong base in water? Explain.

Determine the ammonia concentration of an aqueous solution that has a pH of \(11.50\). The equation for the dissociation of \(\mathrm{NH}_{3}\) \(\left(\mathrm{K}_{\mathrm{b}}=1.8 \times 10^{-5}\right)\) is \(\mathrm{NH}_{3}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftarrows\) \(\mathrm{NH}_{4}^{+}(a q)+\mathrm{OH}^{-}(a q)\)