Chapter 18

Does the \(\mathrm{pH}\) of the solution increase, decrease, or stay the same when you (a) add solid ammonium chloride to a dilute aqueous solution of \(\mathrm{NH}_{3} ?\) (b) add solid sodium acetate to a dilute aqueous solution of acetic acid? (c) add solid NaCl to a dilute aqueous solution of NaOH?

What is the pH of the solution that results from adding \(30.0 \mathrm{mL}\) of \(0.015 \mathrm{M} \mathrm{KOH}\) to \(50.0 \mathrm{mL}\) of \(0.015 \mathrm{M}\) benzoic acid?

What is the pH of the solution that results from adding \(25.0 \mathrm{mL}\) of \(0.12 \mathrm{M} \mathrm{HCl}\) to \(25.0 \mathrm{mL}\) of \(0.43 \mathrm{M} \mathrm{NH}_{3} ?\)

Calculate the \(\mathrm{pH}\) of a solution that has an acetic acid concentration of \(0.050 \mathrm{M}\) and a sodium acetate concentration of \(0.075 \mathrm{M}.\)

Which of the following combinations would be the best to buffer the pH of a solution at approximately \(9 ?\) (a) HCl and NaCl (b) \(\mathrm{NH}_{3}\) and \(\mathrm{NH}_{4} \mathrm{Cl}\) (c) \(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}\) and \(\mathrm{NaCH}_{3} \mathrm{CO}_{2}\)

Which of the following combinations would be the best to buffer the pH of a solution at approximately \(7 ?\) (a) \(\mathrm{H}_{3} \mathrm{PO}_{4}\) and \(\mathrm{NaH}_{2} \mathrm{PO}_{4}\) (b) \(\mathrm{NaH}_{2} \mathrm{PO}_{4}\) and \(\mathrm{Na}_{2} \mathrm{HPO}_{4}\) (c) \(\mathrm{Na}_{2} \mathrm{HPO}_{4}\) and \(\mathrm{Na}_{3} \mathrm{PO}_{4}\)

You dissolve \(0.425 \mathrm{g}\) of \(\mathrm{NaOH}\) in \(2.00 \mathrm{L}\) of a buffer solution that has \(\left[\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\right]=\left[\mathrm{HPO}_{4}^{2-}\right]=0.132 \mathrm{M}.\) What is the pH of the solution before adding NaOH? After adding NaOH?

A buffer solution is prepared by adding 0.125 mol of ammonium chloride to \(5.00 \times 10^{2} \mathrm{mL}\) of \(0.500 \mathrm{M}\) solution of ammonia. (a) What is the pH of the buffer? (b) If 0.0100 mol of \(\mathrm{HCl}\) gas is bubbled into \(5.00 \times 10^{2}\) mL of the buffer, what is the new \(\mathrm{pH}\) of the solution?

You require \(36.78 \mathrm{mL}\) of \(0.0105 \mathrm{M} \mathrm{HCl}\) to reach the equivalence point in the titration of 25.0 mL of aqueous ammonia. (a) What was the concentration of \(\mathrm{NH}_{3}\) in the original ammonia solution? (b) What are the concentrations of \(\mathrm{H}_{3} \mathrm{O}^{+}, \mathrm{OH}^{-},\) and \(\mathrm{NH}_{4}^{+}\) at the equivalence point? (c) What is the pH of the solution at the equivalence point?

Without doing detailed calculations, sketch the curve for the titration of \(30.0 \mathrm{mL}\) of \(0.10 \mathrm{M} \mathrm{NaOH}\) with 0.10 M HCl. Indicate the approximate \(\mathrm{pH}\) at the beginning of the titration and at the equivalence point. What is the total solution volume at the equivalence point?

Without doing detailed calculations, sketch the curve for the titration of \(50 \mathrm{mL}\) of \(0.050 \mathrm{M}\) pyridine, \(\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{N}\) (a weak base), with \(0.10 \mathrm{M}\) HCl. Indicate the approximate \(\mathrm{pH}\) at the beginning of the titration and at the equivalence point. What is the total solution volume at the equivalence point?

You titrate \(25.0 \mathrm{mL}\) of \(0.10 \mathrm{M} \mathrm{NH}_{3}\) with \(0.10 \mathrm{M} \mathrm{HCl}\). (a) What is the pH of the NH \(_{3}\) solution before the titration begins? (b) What is the \(\mathrm{pH}\) at the equivalence point? (c) What is the pH at the halfway point of the titration? (d) What indicator in Figure 18.10 could be used to detect the equivalence point? (e) Calculate the pH of the solution after adding 5.00 \(15.0,20.0,22.0,\) and \(30.0 \mathrm{mL}\) of the acid. Combine this information with that in parts (a)-(c) and plot the titration curve.

Construct a rough plot of \(\mathrm{pH}\) versus volume of base for the titration of \(25.0 \mathrm{mL}\) of \(0.050 \mathrm{M} \mathrm{HCN}\) with \(0.075 \mathrm{M}\) \(\mathrm{NaOH}.\) (a) What is the pH before any \(\mathrm{NaOH}\) is added? (b) What is the pH at the halfway point of the titration? (c) What is the pH when \(95 \%\) of the required \(\mathrm{NaOH}\) has been added? (d) What volume of base, in milliliters, is required to reach the equivalence point? (e) What is the \(\mathrm{pH}\) at the equivalence point? (f) What indicator would be most suitable for this titration? (See Figure 18.10 .) (g) What is the pH when \(105 \%\) of the required base has been added?

Name two insoluble salts of each of the following ions. (a) \(\mathrm{Cl}^{-}\) (b) \(\mathrm{Zn}^{2+}\) (c) \(\mathrm{Fe}^{2+}\)

Name two insoluble salts of each of the following ions. (a) \(\mathrm{SO}_{4}^{2-}\) (b) \(\mathrm{Ni}^{2+}\) (c) \(\mathrm{Br}^{-}\)

Predict whether each of the following is insoluble or soluble in water. (a) \(\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}\) (b) \(\mathrm{Fe}(\mathrm{OH})_{3}\) (c) \(\mathrm{ZnCl}_{2}\) (d) CuS

For each of the following insoluble salts, (1) write a balanced equation showing the equilibrium occurring when the salt is added to water, and (2) write the \(K_{\mathrm{sp}}\) expression. (a) AgCN (b) \(\mathrm{NiCO}_{3}\) (c) \(\mathrm{AuBr}_{3}\)

For each of the following insoluble salts, (1) write a balanced equation showing the equilibrium occurring when the salt is added to water, and (2) write the \(K_{\mathrm{sp}}\) expression. (a) \(\mathrm{PbSO}_{4}\) (b) \(\mathrm{BaF}_{2}\) (c) \(\mathrm{Ag}_{3} \mathrm{PO}_{4}\)

When 1.55 g of solid thallium (I) bromide is added to \(1.00 \mathrm{L}\) of water, the salt dissolves to a small extent. $$\operatorname{TIBr}(\mathrm{s}) \rightleftarrows \mathrm{Tl}^{+}(\mathrm{aq})+\mathrm{Br}^{-}(\mathrm{aq})$$ The thallium(I) and bromide ions in equilibrium with TIBr each have a concentration of \(1.9 \times 10^{-3} \mathrm{M} .\) What is the value of \(K_{\mathrm{sp}}\) for TIBr?

At \(20^{\circ} \mathrm{C},\) a saturated aqueous solution of silver acetate, \(\mathrm{AgCH}_{3} \mathrm{CO}_{2},\) contains \(1.0 \mathrm{g}\) of the silver compound dissolved in \(100.0 \mathrm{mL}\) of solution. Calculate \(K_{\mathrm{sp}}\) for silver acetate. \(\mathrm{AgCH}_{3} \mathrm{CO}_{2}(\mathrm{s}) \rightleftharpoons \mathrm{Ag}^{+}(\mathrm{aq})+\mathrm{CH}_{3} \mathrm{CO}_{2}^{-}(\mathrm{aq})\)

When 250 mg of \(\mathrm{SrF}_{2}\), strontium fluoride, is added to \(1.00 \mathrm{L}\) of water, the salt dissolves to a very small extent. \(\mathrm{SrF}_{2}(\mathrm{s}) \rightleftarrows \mathrm{Sr}^{2+}(\mathrm{aq})+2 \mathrm{F}^{-}(\mathrm{aq})\) At equilibrium, the concentration of \(\mathrm{Sr}^{2+}\) is found to be \(1.03 \times 10^{-3} \mathrm{M} .\) What is the value of \(K_{\mathrm{sp}}\) for \(\mathrm{SrF}_{2} ?\)

Calcium hydroxide, \(\mathrm{Ca}(\mathrm{OH})_{2},\) dissolves in water to the extent of 1.78 g per liter. What is the value of \(K_{\mathrm{sp}}\) for \(\mathrm{Ca}(\mathrm{OH})_{2} ?\) $$\mathrm{Ca}(\mathrm{OH})_{2}(\mathrm{s}) \rightleftharpoons \mathrm{Ca}^{2+}(\mathrm{aq})+2 \mathrm{OH}^{-}(\mathrm{aq})$$

You add \(0.979 \mathrm{g}\) of \(\mathrm{Pb}(\mathrm{OH})_{2}\) to \(1.00 \mathrm{L}\) of pure water at \(25^{\circ} \mathrm{C} .\) The \(\mathrm{pH}\) is \(9.15 .\) Estimate the value of \(K_{\mathrm{sp}}\) for \(\mathrm{Pb}(\mathrm{OH})_{2}.\)

You place \(1.234 \mathrm{g}\) of solid \(\mathrm{Ca}(\mathrm{OH})_{2}\) in \(1.00 \mathrm{L}\) of pure water at \(25^{\circ} \mathrm{C} .\) The \(\mathrm{pH}\) of the solution is found to be \(12.68 .\) Estimate the value of \(K_{\mathrm{sp}}\) for \(\mathrm{Ca}(\mathrm{OH})_{2}.\)

The \(K_{s p}\) value for radium sulfate, \(\operatorname{RaSO}_{4},\) is \(4.2 \times 10^{-11}\) If 25 mg of radium sulfate is placed in \(1.00 \times 10^{2} \mathrm{mL}\) of water, does all of it dissolve? If not, how much dissolves?

Which insoluble compound in each pair should be more soluble in nitric acid than in pure water? (a) \(\mathrm{PbCl}_{2}\) or \(\mathrm{PbS}\) (b) \(\mathrm{Ag}_{2} \mathrm{CO}_{3}\) or \(\mathrm{AgI}\) (c) \(\mathrm{Al}(\mathrm{OH})_{3}\) or \(\mathrm{AgCl}\)

You have a solution that has a lead(II) ion concentration of 0.0012 M. If enough soluble chloride-containing salt is added so that the \(\mathrm{Cl}^{-}\) concentration is \(0.010 \mathrm{M},\) will PbCl \(_{2}\) precipitate?

If the concentration of \(\mathrm{Zn}^{2+}\) in \(10.0 \mathrm{mL}\) of water is \(1.63 \times 10^{-4} \mathrm{M},\) will zinc hydroxide, \(\mathrm{Zn}(\mathrm{OH})_{2},\) precipitate when 4.0 mg of \(\mathrm{NaOH}\) is added?

Will a precipitate of \(\mathrm{Mg}(\mathrm{OH})_{2}\) form when \(25.0 \mathrm{mL}\) of \(0.010 \mathrm{M} \mathrm{NaOH}\) is combined with \(75.0 \mathrm{mL}\) of a \(0.10 \mathrm{M}\) solution of magnesium chloride?

In each of the following cases, decide whether a precipitate will form when mixing the indicated reagents, and write a balanced equation for the reaction. (a) \(\mathrm{NaBr}(\mathrm{aq})+\mathrm{AgNO}_{3}(\mathrm{aq})\) (b) \(\mathrm{KCl}(\mathrm{aq})+\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}(\mathrm{aq})\)

In each of the following cases, decide whether a precipitate will form when mixing the indicated reagents, and write a balanced equation for the reaction. (a) \(\mathrm{Na}_{2} \mathrm{SO}_{4}(\mathrm{aq})+\mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2}(\mathrm{aq})\) (b) \(\mathrm{K}_{3} \mathrm{PO}_{4}(\mathrm{aq})+\mathrm{FeCl}_{3}(\mathrm{aq})\)

If you mix \(48 \mathrm{mL}\) of \(0.0012 \mathrm{M} \mathrm{BaCl}_{2}\) with \(24 \mathrm{mL}\) of \(1.0 \times 10^{-6} \mathrm{M} \mathrm{Na}_{2} \mathrm{SO}_{4},\) will a precipitate of \(\mathrm{BaSO}_{4}\) form?

Calculate the hydronium ion concentration and the \(\mathrm{pH}\) of the solution that results when \(20.0 \mathrm{mL}\) of \(0.15 \mathrm{M}\) acetic acid, \(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H},\) is mixed with \(5.0 \mathrm{mL}\) of \(0.17 \mathrm{M} \mathrm{NaOH}\).

For each of the following cases, decide whether the pH is less than 7 , equal to 7 , or greater than 7 . (a) Equal volumes of \(0.10 \mathrm{M}\) acetic acid, \(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H},\) and \(0.10 \mathrm{M} \mathrm{KOH}\) are mixed. (b) \(25 \mathrm{mL}\) of \(0.015 \mathrm{M} \mathrm{NH}_{3}\) is mixed with \(12 \mathrm{mL}\) of \(0.015 \mathrm{M} \mathrm{HCl}\) (c) \(150 \mathrm{mL}\) of \(0.20 \mathrm{M} \mathrm{HNO}_{3}\) is mixed with \(75 \mathrm{mL}\) of \(0.40 \mathrm{M} \mathrm{NaOH}\) (d) \(25 \mathrm{mL}\) of \(0.45 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}\) is mixed with \(25 \mathrm{mL}\) of \(0.90 \mathrm{M} \mathrm{NaOH}\)

Rank the following compounds in order of increasing solubility in water: \(\mathrm{Na}_{2} \mathrm{CO}_{3}, \mathrm{BaCO}_{3}, \mathrm{Ag}_{2} \mathrm{CO}_{3}.\)

A sample of hard water contains about \(2.0 \times 10^{-3} \mathrm{M}\) \(\mathrm{Ca}^{2+} .\) A soluble fluoride-containing salt such as NaF is added to "fluoridate" the water (to aid in the prevention of dental cavities). What is the maximum concentration of \(\mathrm{F}^{-}\) that can be present without precipitating \(\mathrm{CaF}_{2} ?\) (IMAGE CAN'T COPY)

Describe the effect on the pH of the following actions and explain why there is not an effect: (a) Adding sodium acetate, \(\mathrm{NaCH}_{3} \mathrm{CO}_{2},\) to \(0.100 \mathrm{M}\) \(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}\) (b) Adding \(\mathrm{NaNO}_{3}\) to \(0.100 \mathrm{M} \mathrm{HNO}_{3}\)

The \(\mathrm{Ca}^{2+}\) ion in hard water can be precipitated as \(\mathrm{CaCO}_{3}\) by adding soda ash, \(\mathrm{Na}_{2} \mathrm{CO}_{3} .\) If the calcium ion concentration in hard water is \(0.010 \mathrm{M}\) and if the \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) is added until the carbonate ion concentration is \(0.050 \mathrm{M}\) what percentage of the calcium ions has been removed from the water? (You may neglect carbonate ion hydrolysis.) (IMAGE CAN'T COPY)

Suggest a method for separating a precipitate consisting of a mixture of solid CuS and solid \(\mathrm{Cu}(\mathrm{OH})_{2}.\)

Which of the following barium salts should dissolve in a strong acid such as HCl: \(\mathrm{Ba}(\mathrm{OH})_{2}, \mathrm{BaSO}_{4},\) or \(\mathrm{BaCO}_{3} ?\)

Two acids, each approximately \(0.01 \mathrm{M}\) in concentration, are titrated separately with a strong base. The acids show the following pH values at the equivalence point: \(\mathrm{HA}, \mathrm{pH}=9.5,\) and \(\mathrm{HB}, \mathrm{pH}=8.5.\) (a) Which is the stronger acid, HA or HB? (b) Which of the conjugate bases, \(A^{-}\) or \(B^{-},\) is the stronger base?

Aluminum hydroxide reacts with phosphoric acid to give AIPO \(_{4} .\) The substance is used industrially in adhesives, binders, and cements. (a) Write the balanced equation for the preparation of AlPO \(_{4}\) from aluminum hydroxide and phosphoric acid. (b) If you begin with \(152 \mathrm{g}\) of aluminum hydroxide and \(3.00 \mathrm{L}\) of \(0.750 \mathrm{M}\) phosphoric acid, what is the theoretical yield of AlPO_? (c) If you place \(25.0 \mathrm{g}\) of \(\mathrm{AlPO}_{4}\) in \(1.00 \mathrm{L}\) of water, what are the concentrations of \(\mathrm{Al}^{3+}\) and \(\mathrm{PO}_{4}^{3-}\) at equilibrium? (Neglect hydrolysis of aqueous Al \(^{3+}\) and \(\mathrm{PO}_{4}^{3-}\) ions.) \(K_{\mathrm{sp}}\) for \(\mathrm{AlPO}_{4}\) is \(1.3 \times 10^{-20}\) (d) Does the solubility of AIPO increase ur decrease on adding HCl? Explain. (IMAGE CAN'T COPY)