Chapter 8: Applications of Aqueous Equilibria

A 10.00-g sample of the ionic compound NaA, where A is the anion of a weak acid, was dissolved in enough water to make 100.0 mL of solution and was then titrated with 0.100 M HCl. After 500.0 mL HCl was added, the pH was 5.00. The experimenter found that 1.00 L of 0.100 M HCl was required to reach the stoichiometric point of the titration.

a.What is the molar mass of NaA?

b.Calculate the pH of the solution at the stoichiometric point of the titration.

What mass of $Ca{\left(N{O}_3\right)}_2$must be added to 1.0 L of a 1.0 M HF solution to begin precipitation of$Ca{F}_2\left(s\right)$? Forrole="math" localid="1657802768599" $Ca{F}_2$,role="math" localid="1657802755040" $K_{sp}=4.0\times {10}^{-11}$androle="math" localid="1657802744197" $K_a$for role="math" localid="1657802729930" $HF=7.2\times {10}^{-4}$. Assume no volume change on addition of .data-custom-editor="chemistry" $Ca{\left(N{O}_3\right)}_2\left(s\right)$

The equilibrium constant for the following reaction is.$\mathbf{1}.\mathbf{0}\mathbf{x}{\mathbf{10}}^{23}$

Ethylenediaminetetraacetate

EDTA is used as a complexing agent in chemical analysis. Solutions of EDTA, usually containing the disodiumsalt, ${\mathbf{\text{Na}}}_{\mathbf{2}}{\mathit{H}}_{\mathbf{2}}\mathit{E}\mathit{D}\mathit{T}\mathit{A}$are used to treat heavy metal poisoning. Calculate $\mathbf{\left[}{\mathbf{\text{Cr}}}^{\mathbf{\text{3+}}}\mathbf{\right]}$at equilibrium in a solution originally 0.0010 M in ${\mathbf{\text{Cr}}}^{\mathbf{\text{3+}}}$and 0.050 M in${\mathbf{\text{H}}}_{\mathbf{2}}\mathit{E}\mathit{D}\mathit{T}{\mathit{A}}^{\mathbf{2}\mathbf{-}}$andbuffered at $\mathit{p}\mathit{H}\mathbf{=}\mathbf{6}\mathbf{.00}$

Calculate the concentration of$P{b}^{2+}$in each of thefollowing.

a. a saturated solution of$Pb{\left(OH\right)}_2$,$K_{sp}=1.2\times {10}^{-15}a$

b. a saturated solution of$Pb{\left(OH\right)}_2$buffered at$pH=13.00$

c. Ethylenediaminetetraacetate$\left(EDT{A}^{4-}\right)$is used as acomplexing agent in chemical analysis and has thefollowing structure:

Solutions of$EDT{A}^{4-}$are used to treat heavy metal poisoning by removing the heavy metal in the form of a soluble complex ion. The reaction of$EDT{A}^{4-}$with$P{b}^{2+}$is

$P{b}^{2+}\left(aq\right)+EDT{A}^{4-}\left(aq\right)\rightleftharpoons PbEDT{A}^{2-}\left(q\right)K=1.1\times {10}^{18}$
Consider a solution with 0.010 mole of$Pb{\left(N{O}_3\right)}_2$addedto 1.0 L of an aqueous solution buffered at$pH=13.00$and containing 0.050 M.$N{a}_{4}EDTA$ Does$Pb{\left(OH\right)}_2$precipitate from this solution?

Consider saturated solutions of the following compounds.

a.$\mathit{M}\mathit{g}{\mathbf{\left(}\mathbf{O}\mathbf{H}\mathbf{\right)}}_{\mathbf{2}}$

b.$\mathit{C}\mathit{d}{\mathbf{\left(}\mathbf{O}\mathbf{H}\mathbf{\right)}}_{\mathbf{2}}$

c.$\mathit{P}\mathit{b}{\mathbf{\left(}\mathbf{O}\mathbf{H}\mathbf{\right)}}_{\mathbf{2}}$

Calculate the pH of each saturated solution.

A certain acetic acid solution has.$\mathit{p}\mathit{H}\mathbf{=}\mathbf{2}\mathbf{.68}$ Calculate the volume of 0.0975 M KOH required to “neutralize” 25.0 mL of this solution.

Calculate the volume of $\mathbf{1}\mathbf{.50}\mathbf{\times }{\mathbf{10}}^{\mathbf{-}\mathbf{2}}\mathit{M}\mathit{N}\mathit{a}\mathit{O}\mathit{H}$that must be added to 500.0 mL of$\mathbf{0}\mathbf{.200}\mathit{M}\mathit{H}\mathit{C}\mathit{l}$to give a solution that has$\mathit{p}\mathit{H}\mathbf{=}\mathbf{2}\mathbf{.15}$.

A 0.400 M solution of ammonia was titrated with hydrochloric acid to the equivalence point, where the total volume was 1.50 times the original volume. At what pH does the equivalence point occur?

A student intends to titrate a solution of a weak monoprotic acid with a sodium hydroxide solution but reverses the two solutions and places the weak acid solution in the buret. After 23.75 mL of the weak acid solution has been added to 50.0 mL of the 0.100 M NaOH solution, the pH of the resulting solution is 10.50. Calculate the original concentration of the solution of weak acid.

The active ingredient in aspirin is acetylsalicylic acid. A 2.51-g sample of acetylsalicylic acid required 27.36 mL of 0.5106 M NaOH for complete reaction. Addition of 15.44 mL of 0.4524 M HCl to the flask containing the aspirin and the sodium hydroxide produced a mixture with $\mathbf{\text{pH\hspace{0.17em}=\hspace{0.17em}3.48}}$. Find the molar mass of acetylsalicylic acid and its${\mathbf{\text{K}}}_{\mathbf{\text{a}}}$value. Acetylsalicylic acid is a monoprotic acid.