Chapter 4

Can a solid ever be a solvent? Explain.

What is the molarity of a solution that contains 1.00 mmol of solute per milliliter of solution?

Calculate the molarity of each of the following solutions: a. \(0.56 \mathrm{mol}\) of \(\mathrm{BaCl}_{2}\) in \(100.0 \mathrm{mL}\) of solution b. 0.200 mol of \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) in \(200.0 \mathrm{mL}\) of solution c. 0.325 mol of \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\) in \(250.0 \mathrm{mL}\) of solution d. \(1.48 \mathrm{mol}\) of \(\mathrm{KNO}_{3}\) in \(250.0 \mathrm{mL}\) of solution

Calculate the molarity of each of the following solutions: a. 0.150 mol of urea \(\left(\mathrm{CH}_{4} \mathrm{N}_{2} \mathrm{O}\right)\) in \(250.0 \mathrm{mL}\) of solution b. \(1.46 \mathrm{mol}\) of \(\mathrm{NaC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\) in \(1.000 \mathrm{L}\) of solution c. 1.94 mol of methanol \(\left(\mathrm{CH}_{3} \mathrm{OH}\right)\) in \(5.000 \mathrm{L}\) of solution d. 0.045 mol of sucrose \(\left(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\right)\) in \(50.0 \mathrm{mL}\) of solution

Calculate the molarity of each of the following ions: a. \(0.33 \mathrm{g} \mathrm{Na}^{+}\) in \(100.0 \mathrm{mL}\) of solution b. \(0.38 \mathrm{g} \mathrm{Cl}^{-}\) in \(100.0 \mathrm{mL}\) of solution c. \(0.46 \mathrm{g} \mathrm{SO}_{4}^{2-}\) in \(50.0 \mathrm{mL}\) of solution d. \(0.40 \mathrm{g} \mathrm{Ca}^{2+}\) in \(50.0 \mathrm{mL}\) of solution

Calculate the molarity of each of the following solutions: a. \(64.7 \mathrm{g}\) LiCl in \(250.0 \mathrm{mL}\) of solution b. \(29.3 \mathrm{g} \mathrm{NiSO}_{4}\) in \(200.0 \mathrm{mL}\) of solution c. \(50.0 \mathrm{g} \mathrm{KCN}\) in \(500.0 \mathrm{mL}\) of solution d. \(0.155 \mathrm{g} \mathrm{AgNO}_{3}\) in \(100.0 \mathrm{mL}\) of solution

How many grams of solute are needed to prepare each of the following solutions? a. \(1.000 \mathrm{L}\) of \(0.200 M \mathrm{NaCl}\) b. \(250.0 \mathrm{mL}\) of \(0.125 M \mathrm{CuSO}_{4}\) c. \(500.0 \mathrm{mL}\) of \(0.400 M \mathrm{CH}_{3} \mathrm{OH}\)

How many grams of solute are needed to prepare each of the following solutions? a. \(500.0 \mathrm{mL}\) of \(0.250 M \mathrm{KBr}\) b. \(25.0 \mathrm{mL}\) of \(0.200 M \mathrm{NaNO}_{3}\) c. \(100.0 \mathrm{mL}\) of \(0.375 M \mathrm{CH}_{3} \mathrm{OH}\)

River Water The Mackenzie River in northern Canada contains, on average, \(0.820 \mathrm{m} \mathrm{M} \mathrm{Ca}^{2+}, 0.430 \mathrm{m} \mathrm{M} \mathrm{Mg}^{2+}\) \(0.300 \mathrm{mM} \mathrm{Na}^{+}, 0.0200 \mathrm{MK}^{+}, 0.250 \mathrm{mM} \mathrm{Cl}^{-}, 0.380 \mathrm{mM}\) \(\mathrm{SO}_{4}^{2-},\) and \(1.82 \mathrm{m} \mathrm{M} \mathrm{HCO}_{3}^{-} .\) What, on average, is the total mass of these ions in 2.75 L of Mackenzie River water?

Toxicity of Metal lons Zinc, copper, lead, and mercury ions are toxic to Atlantic salmon at concentrations of \(6.42 \times 10^{-2} \mathrm{m} M, 7.16 \times 10^{-3} \mathrm{m} M, 0.965 \mathrm{m} M,\) and \(5.00 \times 10^{-2} \mathrm{m} M,\) respectively. What are the corresponding concentrations in milligrams per liter?

Calculate the number of moles of solute contained in the following volumes of aqueous solutions of four pesticides: a. \(0.400 \mathrm{L}\) of \(0.024 M\) lindane b. \(1.65 \mathrm{L}\) of \(0.473 \mathrm{m} M\) dieldrin c. \(25.8 \mathrm{L}\) of \(3.4 \mathrm{m} M\) DDT d. \(154 \mathrm{L}\) of \(27.4 \mathrm{m} \mathrm{M}\) aldrin

Hemoglobin in Blood A typical adult body contains \(6.0 \mathrm{L}\) of blood. The hemoglobin content of blood is about \(15.5 \mathrm{g} / 100.0 \mathrm{mL}\) of blood. The approximate molar mass of hemoglobin is \(64,500 \mathrm{g} / \mathrm{mol} .\) How many moles of hemoglobin are present in a typical adult?

Pesticides in the Environment Pesticide concentrations in the Rhine River between Germany and France between 1969 and 1975 averaged \(0.55 \mathrm{mg} / \mathrm{L}\) of hexachlorobenzene \(\left(\mathrm{C}_{6} \mathrm{Cl}_{6}\right), 0.06 \mathrm{mg} / \mathrm{L}\) of dieldrin \(\left(\mathrm{C}_{12} \mathrm{H}_{8} \mathrm{Cl}_{6} \mathrm{O}\right),\) and \(1.02 \mathrm{mg} / \mathrm{L}\) of hexachlorocyclohexane \(\left(\mathrm{C}_{6} \mathrm{H}_{6} \mathrm{Cl}_{6}\right) .\) Express these concentrations in \(\mathrm{ppb}\) and in millimoles per liter.

Gases Found in Air Sulfur hexafluoride, \(\mathrm{SF}_{6}\), is used in electrical transformers. Like \(\mathrm{NF}_{3}\), it has a potential impact on climate. Between 1978 and \(2012,\) the concentration of \(\mathrm{SF}_{6}\) increased from 0.51 parts per trillion (ppt) to 7.48 ppt. How many more molecules of \(\mathrm{SF}_{6}\) were found in one liter of air in 2012 than in \(1978 ?\) ( 1 mole of gas \(=22.4\) L of gas.)

The concentration of copper(II) sulfate in one brand of soluble plant fertilizer is \(0.07 \%\) by mass. If a \(20 \mathrm{g}\) sample of this fertilizer is dissolved in \(2.0 \mathrm{L}\) of solution, what is the molarity of \(\mathrm{Cu}^{2+} ?\)

For which of the following compounds is it possible to make a \(1.0 M\) solution at \(20^{\circ} \mathrm{C} ?\) a. \(\mathrm{CuSO}_{4},\) solubility \(=32.0 \mathrm{g} / 100 \mathrm{mL}\) b. \(\mathrm{Ba}(\mathrm{OH})_{2},\) solubility \(=3.9 \mathrm{g} / 100 \mathrm{mL}\) c. \(\mathrm{FeCl}_{2}\), solubility \(=68.5 \mathrm{g} / 100 \mathrm{mL}\) d. \(\mathrm{Ca}(\mathrm{OH})_{2},\) solubility \(=0.173 \mathrm{g} / 100 \mathrm{mL}\)

Calculate the final concentrations of the following aqueous solutions after each has been diluted to a final volume of \(25.0 \mathrm{mL}:\) a. \(3.00 \mathrm{mL}\) of \(0.175 M \mathrm{K}^{+}\) b. \(2.50 \mathrm{mL}\) of \(10.6 \mathrm{m} M \mathrm{LiCl}\) c. \(15.00 \mathrm{mL}\) of \(7.24 \times 10^{-2} \mathrm{m} M \mathrm{Zn}^{2+}\)

Dilution of Adult-Strength Cough Syrup A standard dose of an over-the-counter cough suppressant for adults is \(20.0 \mathrm{mL} .\) A portion this size contains \(35 \mathrm{mg}\) of the active pharmaceutical ingredient (API). Your pediatrician says you may give this medication to your 6-year-old child, but the child may take only \(10.0 \mathrm{mL}\) at a time and receive a maximum of 4.00 mg of the API. What is the concentration in \(\mathrm{mg} / \mathrm{mL}\) of the adult-strength medication, and how many millimeters of it would you need to dilute to make 100.0 mL of child-strength cough syrup?

The concentration of \(\mathrm{Na}^{+}\) in seawater, \(0.481 M,\) is higher than in the cytosol, the fluid inside human cells \((12 \mathrm{mM})\) How much water must be added to 1.50 mL of seawater to make the \(\mathrm{Na}^{+}\) concentration equal to that found in the cytosol? Assume the volumes are additive.

Water is allowed to evaporate from \(100.0 \mathrm{mL}\) of \(0.24 M\) \(\mathrm{Na}_{2} \mathrm{SO}_{4}\) until the solution volume is \(60.0 \mathrm{mL} .\) What is the molar concentration of the evaporated solution?

If the absorbance of a solution of copper ion decreases by \(45 \%\) upon dilution, how much water was added to \(15.0 \mathrm{mL}\) of a \(1.00 M\) solution of \(\mathrm{Cu}^{2+} ?\)

By what percentage does the absorbance decrease if \(12.25 \mathrm{mL}\) of water is added to a 16.75 mL sample of \(0.500 M \mathrm{Cr}^{3+} ?\)

The reaction of \(\mathrm{SnCl}_{2}(a q)\) with \(\mathrm{Pt}^{4+}(a q)\) in aqueous \(\mathrm{HCl}\) yields a yellow-orange solution of a 1: 1 Pt-Sn compound with a molar absorptivity \((\varepsilon)\) of \(1.3 \times 10^{4} M^{-1} \mathrm{cm}^{-1} .\) What is the absorbance in a cell with a path length of \(1.00 \mathrm{cm}\) of a solution prepared by adding \(100 \mathrm{mL}\) of an aqueous solution of \(5.2 \mathrm{mg}\left(\mathrm{NH}_{4}\right)_{2} \mathrm{PtCl}_{6}\) to \(100 \mathrm{mL}\) of an aqueous solution of \(2.2 \mathrm{mg} \mathrm{SnCl}_{2} ?\)

The reaction of \(\mathrm{SnCl}_{2}(a q)\) with \(\mathrm{RhCl}_{3}(a q)\) in aqueous \(\mathrm{HCl}\) yields a red solution of a 1: 1 Rh-Sn compound. If a solution prepared by adding \(150 \mathrm{mL}\) of a \(0.272 \mathrm{m} M\) aqueous solution of \(\mathrm{SnCl}_{2}\) to \(50 \mathrm{mL}\) of an aqueous solution of \(8.5 \mathrm{mg} \mathrm{RhCl}_{3}\) has an absorbance of \(0.85,\) as measured in a \(1.00 \mathrm{cm}\) cell, what is the molar absorptivity of the red compound?

A solution of table salt is a good conductor of electricity, but a solution containing an equal molar concentration of table sugar is not. Why?

Corrosion at Sea Metallic fixtures on the bottom of a ship corrode more quickly in seawater than in freshwater. Why?

Explain why liquid methanol, \(\mathrm{CH}_{3} \mathrm{OH},\) cannot conduct electricity, whereas molten \(\mathrm{NaOH}\) can.

Fuel Cells The electrolyte in an electricity-generating device called a fuel cell consists of a mixture of \(\mathrm{Li}_{2} \mathrm{CO}_{3}\) and \(\mathrm{K}_{2} \mathrm{CO}_{3}\) heated to \(650^{\circ} \mathrm{C} .\) At this temperature the ionic solids melt. Explain how this mixture of molten carbonates can conduct electricity.

Rank the following solutions on the basis of their ability to conduct electricity, starting with the most conductive: (a) \(1.0 \mathrm{M} \mathrm{NaCl} ;\) (b) \(1.2 \mathrm{M} \mathrm{KCl} ;\) (c) \(1.0 \mathrm{M} \mathrm{Na}_{2} \mathrm{SO}_{4}\) (d) \(0.75 M\) LiCl.

Rank the conductivities of \(1 M\) aqueous solutions of each of the following solutes, starting with the most conductive: (a) acetic acid; (b) methanol; (c) sucrose (table sugar); (d) hydrochloric acid.

Calculate the molarity of \(\mathrm{Na}^{+}\) ions in a \(0.025 \mathrm{M}\) aqueous solution of: (a) \(\mathrm{NaBr} ;\) (b) \(\mathrm{Na}_{2} \mathrm{SO}_{4} ;\) (c) \(\mathrm{Na}_{3} \mathrm{PO}_{4}\)

Calculate the molarity of each ion in a \(0.025 M\) aqueous solution of: (a) \(\mathrm{KCl} ;\) (b) \(\mathrm{CuSO}_{4} ;\) (c) \(\mathrm{CaCl}_{2}\)

Which of the following solutions has the greatest number of particles (atoms or ions) of solute per liter? (a) \(1 M \mathrm{NaCl} ;\) (b) \(1 M \mathrm{CaCl}_{2} ;\) (c) \(1 M\) ethanol; (d) \(1 M\) acetic acid

Which of the following solutions contains the most solute particles per liter? (a) \(1 M \mathrm{KBr} ;\) (b) \(1 M \mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2} ;\) (c) \(4 M\) ethanol; (d) \(4 M\) acetic acid

What name is given to a proton donor?

What is the difference between a strong acid and a weak acid?

Identify each compound as either a weak acid or a strong acid in aqueous solution: (a) HNO \(_{3} ;\) (b) HNO \(_{2}\) (c) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{COOH} ;(\mathrm{d}) \mathrm{H}_{2} \mathrm{SO}_{4}\)

Why is HSO \(_{4}^{-}(a q)\) a weaker acid than \(\mathrm{H}_{2} \mathrm{SO}_{4}(a q) ?\)

What name is given to a proton acceptor?

What is the difference between a strong base and a weak base?

Identify each compound as either a weak base or a strong base in aqueous solution: (a) \(\mathrm{Ca}(\mathrm{OH})_{2} ;\) (b) \(\mathrm{NH}_{3}\) (c) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NH}_{2} ;\) (d) \(\mathrm{NaOH}\)

Write the net ionic equation for the neutralization of a strong acid by a strong base.

For each of the following acid-base reactions, identify the acid and the base, and then write the overall ionic and net ionic equations. a. \(\mathrm{H}_{2} \mathrm{SO}_{4}(a q)+\mathrm{Ca}(\mathrm{OH})_{2}(a q) \rightarrow \mathrm{CaSO}_{4}(s)+2 \mathrm{H}_{2} \mathrm{O}(\ell)\) b. \(\operatorname{PbCO}_{3}(s)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q) \rightarrow\) \(\mathrm{PbSO}_{4}(s)+\mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(\ell)\) c. \(\mathrm{Ca}(\mathrm{OH})_{2}(s)+2 \mathrm{CH}_{3} \mathrm{COOH}(a q) \rightarrow\) \(\mathrm{Ca}\left(\mathrm{CH}_{3} \mathrm{COO}\right)_{2}(a q)+2 \mathrm{H}_{2} \mathrm{O}(a q)\)

Complete and balance each of the following neutralization reactions, name the products, and write the overall ionic and net ionic equations. a. \(\mathrm{HBr}(a q)+\mathrm{KOH}(a q) \rightarrow\) b. \(\mathrm{H}_{3} \mathrm{PO}_{4}(a q)+\mathrm{Ba}(\mathrm{OH})_{2}(a q) \rightarrow\) c. \(\mathrm{Al}(\mathrm{OH})_{3}(s)+\mathrm{HCl}(a q) \rightarrow\) d. \(\mathrm{CH}_{3} \mathrm{COOH}(a q)+\mathrm{Sr}(\mathrm{OH})_{2}(a q) \rightarrow\)

Write a balanced molecular equation and a net ionic equation for the following reactions: a. Solid magnesium hydroxide reacts with a solution of sulfuric acid. b. Solid magnesium carbonate reacts with a solution of hydrochloric acid. c. Ammonia gas reacts with hydrogen chloride gas. d. Gaseous sulfur trioxide is dissolved in water and reacts with a solution of sodium hydroxide.

Write a balanced molecular equation and a net ionic equation for the following reactions: a. Solid aluminum hydroxide reacts with a solution of hydrobromic acid. b. A solution of sulfuric acid reacts with solid sodium carbonate. c. A solution of calcium hydroxide reacts with a solution of nitric acid. d. Solid potassium oxide is dissolved in water and reacts with a solution of sulfuric acid.

Toxicity of Lead Pigments The use of lead(II) carbonate and lead(II) hydroxide as white pigments in paint was discontinued because children have been known to eat paint chips. The pigments dissolve in stomach acid, and lead ions enter the nervous system and interfere with neurotransmissions in the brain, causing neurological disorders. Using net ionic equations, show why lead(II) carbonate and lead(II) hydroxide dissolve in acidic solutions.

How many milliliters of \(0.250 M\) NaOH are required to neutralize the following solutions? a. \(60.0 \mathrm{mL}\) of \(0.0750 M \mathrm{HCl}\) b. \(35.0 \mathrm{mL}\) of \(0.226 M \mathrm{HNO}_{3}\) c. \(75.0 \mathrm{mL}\) of \(0.190 M \mathrm{H}_{2} \mathrm{SO}_{4}\)

How many milliliters of \(0.250 M\) HNO \(_{3}\) are needed to neutralize the following solutions? a. \(25.0 \mathrm{mL}\) of \(0.395 M \mathrm{KOH}\) b. \(78.6 \mathrm{mL}\) of \(0.0100 M \mathrm{Al}(\mathrm{OH})_{3}\) c. \(65.9 \mathrm{mL}\) of \(0.475 M \mathrm{NaOH}\)

The solubility of slaked lime, \(\mathrm{Ca}(\mathrm{OH})_{2},\) in water at \(20^{\circ} \mathrm{C}\) is \(0.185 \mathrm{g} / 100.0 \mathrm{mL} .\) What volume of \(0.00100 M \mathrm{HCl}\) is needed to neutralize \(10.0 \mathrm{mL}\) of a saturated \(\mathrm{Ca}(\mathrm{OH})_{2}\) solution?