Solved: A pharmaceutical preparation made with ethanol (C2H5OH) is contaminated with

Describe how properties of seawater illustrate the two characteristics that define mixtures.

What types of intermolecular forces give rise to hydration shells in an aqueous solution of sodium chloride?

Acetic acid is miscible with water. Would you expect carboxylic acids with general formula CH3(CH2)nCOOH to become more or less water soluble as n increases? Explain.

Which would you expect to be more effective as a soap, sodium acetate or sodium stearate? Explain.

Hexane and methanol are miscible as gases but only slightly soluble in each other as liquids. Explain.

Hydrogen chloride (HCl) gas is much more soluble than propane gas (C3H8) in water, even though HCl has a lower boiling point. Explain. (grouped in similar pairs)

Which gives the more concentrated solution, (a) KNO3 in H2O or (b) KNO3 in carbon tetrachloride (CCl4)? Explain.

Which gives the more concentrated solution, stearic acid [CH3(CH2)16COOH] in (a) H2O or (b) CCl4? Explain.

What is the strongest type of intermolecular force between solute and solvent in each solution? (a) CsCl(s) in H2O(l) (b) (c) CH3OH(l) in CCl4(l)

What is the strongest type of intermolecular force between solute and solvent in each solution? (a) Cu(s) in Ag(s) (b) CH3Cl(g) in CH3OCH3(g) (c) CH3CH3(g) in CH3CH2CH2NH2(l)

What is the strongest type of intermolecular force between solute and solvent in each solution? (a) CH3OCH3(g) in H2O(l) (b) Ne(g) in H2O(l) (c) N2(g) in C4H10(g)

What is the strongest type of intermolecular force between solute and solvent in each solution? (a) C6H14(l) in C8H18(l) (b) H2C O(g) in CH3OH(l) (c) Br2(l) in CCl4(l)

Which member of each pair is more soluble in diethyl ether? Why? (a) NaCl(s) or HCl(g) (b) (c) MgBr2(s) or CH3CH2MgBr(s)

Which member of each pair is more soluble in water? Why? (a) CH3CH2OCH2CH3(l) or CH3CH2OCH3(g) (b) CH2Cl2(l) or CCl4(l) (c)

The dictionary defines homogeneous as uniform in composition throughout. River water is a mixture of dissolved compounds, such as calcium bicarbonate, and suspended soil particles. Is river water homogeneous? Explain.

Gluconic acid is a derivative of glucose used in cleaners and in the dairy and brewing industries. Caproic acid is a carboxylic acid used in the flavoring industry. Although both are six-carbon acids (see structures below), gluconic acid is soluble in water and nearly insoluble in hexane, whereas caproic acid has the opposite solubility behavior. Explain.

Name three intermolecular forces that stabilize the shape of a soluble, globular protein, and explain how they act.

Name three intermolecular forces that stabilize the shape of DNA, and explain how they act.

Is the sodium salt of propanoic acid as effective a soap as sodium stearate? Explain.

What intermolecular forces stabilize a lipid bilayer?

In what way do proteins embedded in a membrane differ structurally from soluble proteins?

How can wood be so strong if it consists of cellulose chains held together by relatively weak H bonds?

Histones are proteins that control gene function by attaching through salt links to exterior regions of DNA. Name an amino acid whose side chain is often found on the exterior of histones.

What is the relationship between solvation and hydration?

For a general solvent, which enthalpy terms in the thermochemical solution cycle are combined to obtain Hsolvation?

(a) What is the charge density of an ion, and what two properties of an ion affect it? (b) Arrange the following in order of increasing charge density: (c) How do the two properties in part (a) affect the ionic heat of hydration, _Hhydr?

For _Hsoln to be very small, what quantities must be nearly equal in magnitude? Will their signs be the same or opposite?

Water is added to a flask containing solid NH4Cl. As the salt dissolves, the solution becomes colder. (a) Is the dissolving of NH4Cl exothermic or endothermic? (b) Is the magnitude of _Hlattice of NH4Cl larger or smaller than the combined _Hhydr of the ions? Explain. (c) Given the answer to (a), why does NH4Cl dissolve in water?

An ionic compound has a highly negative _Hsoln in water. Would you expect it to be very soluble or nearly insoluble in water? Explain in terms of enthalpy and entropy changes. (grouped in similar pairs)

Sketch a qualitative enthalpy diagram for the process of dissolving KCl(s) in H2O (endothermic).

Sketch a qualitative enthalpy diagram for the process of dissolving NaI(s) in H2O (exothermic).

Which ion in each pair has greater charge density? Explain. (a) Na_ or Cs_ (b) Sr2_ or Rb_ (c) Na_ or Cl_ (d) O2_ or F_ (e) OH_ or SH_ (f) Mg2_ or Ba2_ (g) Mg2_ or Na_ (h) NO3 _ or CO3 2_

Which ion has the lower ratio of charge to volume? Explain. (a) Br_ or I_ (b) Sc3_ or Ca2_ (c) Br_ or K_ (d) S2_ or Cl_ (e) Sc3_ or Al3_ (f) SO4 2_ or ClO4 _ (g) Fe3_ or Fe2_ (h) Ca2_ or K_

Which has the larger _Hhydr in each pair of Problem 13.32?

Which has the smaller _Hhydr in each pair of Problem 13.33?

(a) Use the following data to calculate the combined heat of hydration for the ions in potassium bromate (KBrO3): _Hlattice _ 745 kJ/mol _Hsoln _ 41.1 kJ/mol (b) Which ion contributes more to the answer to part (a)? Why?

(a) Use the following data to calculate the combined heat of hydration for the ions in sodium acetate (NaC2H3O2): _Hlattice _ 763 kJ/mol _Hsoln _ 17.3 kJ/mol (b) Which ion contributes more to the answer to part (a)? Why?

State whether the entropy of the system increases or decreases in each of the following processes: (a) Gasoline burns in a car engine. (b) Gold is extracted and purified from its ore. (c) Ethanol (CH3CH2OH) dissolves in 1-propanol (CH3CH2CH2OH).

State whether the entropy of the system increases or decreases in each of the following processes: (a) Pure gases are mixed to prepare an anesthetic. (b) Electronic-grade silicon is prepared from sand. (c) Dry ice (solid CO2) sublimes.

Besides its use in making black-and-white film, silver nitrate (AgNO3) is used similarly in forensic science. The NaCl left behind in the sweat of a fingerprint is treated with AgNO3 solution to form AgCl. This precipitate is developed to show the black-and-white fingerprint pattern. Given _Hlattice of AgNO3 _ 822 kJ/mol and _Hhydr__799 kJ/mol, calculate its _Hsoln. (Sample Problem 13.2)

You are given a bottle of solid X and three aqueous solutions of Xone saturated, one unsaturated, and one supersaturated. How would you determine which solution is which?

Potassium permanganate (KMnO4) has a solubility of 6.4 g/100 g of H2O at 20_C and a curve of solubility vs. temperature that slopes upward to the right. How would you prepare a supersaturated solution of KMnO4?

Why does the solubility of any gas in water decrease with rising temperature? (grouped in similar pairs)

For a saturated aqueous solution of each of the following at 20_C and 1 atm, will the solubility increase, decrease, or stay the same when the indicated change occurs? (a) O2(g), increase P (b) N2(g), increase V

For a saturated aqueous solution of each of the following at 20_C and 1 atm, will the solubility increase, decrease, or stay the same when the indicated change occurs? (a) He(g), decrease T (b) RbI(s), increase P

The Henrys law constant (kH) for O2 in water at 20_C is 1.28_10_3 mol/L_atm. (a) How many grams of O2 will dissolve in 2.50 L of H2O that is in contact with pure O2 at 1.00 atm? (b) How many grams of O2 will dissolve in 2.50 L of H2O that is in contact with air, where the partial pressure of O2 is 0.209 atm?

Argon makes up 0.93% by volume of air. Calculate its solubility (mol/L) in water at 20_C and 1.0 atm. The Henrys law constant for Ar under these conditions is 1.5_10_3 mol/L_atm.

Caffeine is about 10 times as soluble in hot water as in cold water. A chemist puts a hot-water extract of caffeine into an ice bath, and some caffeine crystallizes. Is the remaining solution saturated, unsaturated, or supersaturated?

The partial pressure of CO2 gas above the liquid in a bottle of champagne at 20_C is 5.5 atm. What is the solubility of CO2 in champagne? Assume Henrys law constant is the same for champagne as for water: at 20_C, kH _ 3.7_10_2 mol/L_atm.

Respiratory problems are treated with devices that deliver air with a higher partial pressure of O2 than normal air. Why? (Sample Problems 13.3 to 13.5)

Explain the difference between molarity and molality. Under what circumstances would molality be a more accurate measure of the concentration of a prepared solution than molarity? Why?

Which way of expressing concentration includes (a) volume of solution; (b) mass of solution; (c) mass of solvent?

A solute has a solubility in water of 21 g/kg solvent. Is this value the same as 21 g/kg solution? Explain.

You want to convert among molarity, molality, and mole fraction of a solution. You know the masses of solute and solvent and the volume of solution. Is this enough information to carry out all the conversions? Explain.

When a solution is heated, which ways of expressing concentration change in value? Which remain unchanged? Explain.

Calculate the molarity of each aqueous solution: (a) 32.3 g of table sugar (C12H22O11) in 100. mL of solution (b) 5.80 g of LiNO3 in 505 mL of solution

Calculate the molarity of each aqueous solution: (a) 0.82 g of ethanol (C2H5OH) in 10.5 mL of solution (b) 1.27 g of gaseous NH3 in 33.5 mL of solution

Calculate the molarity of each aqueous solution: (a) 78.0 mL of 0.240 M NaOH diluted to 0.250 L with water (b) 38.5 mL of 1.2 M HNO3 diluted to 0.130 L with water

Calculate the molarity of each aqueous solution: (a) 25.5 mL of 6.25 M HCl diluted to 0.500 L with water (b) 8.25 mL of 2.00_10_2 M KI diluted to 12.0 mL with water

How would you prepare the following aqueous solutions? (a) 365 mL of 8.55_10_2 M KH2PO4 from solid KH2PO4 (b) 465 mL of 0.335 M NaOH from 1.25 M NaOH

How would you prepare the following aqueous solutions? (a) 2.5 L of 0.65 M NaCl from solid NaCl (b) 15.5 L of 0.3 M urea [(NH2)2CoeO] from 2.1 M urea

How would you prepare the following aqueous solutions? (a) 1.40 L of 0.288 M KBr from solid KBr (b) 255 mL of 0.0856 M LiNO3 from 0.264 M LiNO3

How would you prepare the following aqueous solutions? (a) 57.5 mL of 1.53_10_3 M Cr(NO3)3 from solid Cr(NO3)3 (b) 5.8_103 m3 of 1.45 M NH4NO3 from 2.50 M NH4NO3

Calculate the molality of the following: (a) A solution containing 85.4 g of glycine (NH2CH2COOH) dissolved in 1.270 kg of H2O (b) A solution containing 8.59 g of glycerol (C3H8O3) in 77.0 g of ethanol (C2H5OH)

Calculate the molality of the following: (a) A solution containing 174 g of HCl in 757 g of H2O (b) A solution containing 16.5 g of naphthalene (C10H8) in 53.3 g of benzene (C6H6)

What is the molality of a solution consisting of 44.0 mL of benzene (C6H6; d _ 0.877 g/mL) in 167 mL of hexane (C6H14; d _ 0.660 g/mL)?

What is the molality of a solution consisting of 2.66 mL of carbon tetrachloride (CCl4; d _ 1.59 g/mL) in 76.5 mL of methylene chloride (CH2Cl2; d _ 1.33 g/mL)?

How would you prepare the following aqueous solutions? (a) 3.10_102 g of 0.125 m ethylene glycol (C2H6O2) from ethylene glycol and water (b) 1.20 kg of 2.20 mass % HNO3 from 52.0 mass % HNO3

How would you prepare the following aqueous solutions? (a) 1.50 kg of 0.0355 m ethanol (C2H5OH) from ethanol and water (b) 445 g of 13.0 mass % HCl from 34.1 mass % HCl

A solution contains 0.35 mol of isopropanol (C3H7OH) dissolved in 0.85 mol of water. (a) What is the mole fraction of isopropanol? (b) The mass percent? (c) The molality?

A solution contains 0.100 mol of NaCl dissolved in 8.60 mol of water. (a) What is the mole fraction of NaCl? (b) The mass percent? (c) The molality?

What mass of cesium bromide must be added to 0.500 L of water (d _ 1.00 g/mL) to produce a 0.400 m solution? What are the mole fraction and the mass percent of CsBr?

What are the mole fraction and the mass percent of a solution made by dissolving 0.30 g of KI in 0.400 L of water (d _ 1.00 g/mL)?

Calculate the molality, molarity, and mole fraction of NH3 in an 8.00 mass % aqueous solution (d _ 0.9651 g/mL).

Calculate the molality, molarity, and mole fraction of FeCl3 in a 28.8 mass % aqueous solution (d _ 1.280 g/mL).

Wastewater from a cement factory contains 0.25 g of Ca2_ ion and 0.056 g of Mg2_ ion per 100.0 L of solution. The solution density is 1.001 g/mL. Calculate the Ca2_ and Mg2_ concentrations in ppm (by mass).

An automobile antifreeze mixture is made by mixing equal volumes of ethylene glycol (d _ 1.114 g/mL; _ _ 62.07 g/mol) and water (d _ 1.00 g/mL) at 20_C. The density of the mixture is 1.070 g/mL. Express the concentration of ethylene glycol as: (a) Volume percent (b) Mass percent (c) Molarity (d) Molality (e) Mole fraction (Sample Problems 13.6 to 13.9)

The chemical formula of a solute does not affect the extent of the solutions colligative properties. What characteristic of a solute does affect these properties? Name a physical property of a solution that is affected by the chemical formula of the solute.

What is a nonvolatile nonelectrolyte? Why is this type of solute the simplest case for examining colligative properties?

In what sense is a strong electrolyte strong? What property of the substance makes it a strong electrolyte?

Express Raoults law in words. Is Raoults law valid for a solution of a volatile solute? Explain.

What are the most important differences between the phase diagram of a pure solvent and the phase diagram of a solution of that solvent?

Is the composition of the vapor at the top of a fractionating column different from the composition at the bottom? Explain.

Is the boiling point of 0.01 m KF(aq) higher or lower than that of 0.01 m glucose(aq)? Explain.

Which aqueous solution has a boiling point closer to its predicted value, 0.050 m NaF or 0.50 m KCl? Explain.

Which aqueous solution has a freezing point closer to its predicted value, 0.01 m NaBr or 0.01 m MgCl2? Explain.

The freezing point depression constants of the solvents cyclohexane and naphthalene are 20.1_C/m and 6.94_C/m, respectively. Which solvent would give a more accurate result if you are using freezing point depression to determine the molar mass of a substance that is soluble in either one? Why? (grouped in similar pairs)

Classify the following substances as strong electrolytes, weak electrolytes, or nonelectrolytes: (a) Hydrogen chloride (HCl) (b) Potassium nitrate (KNO3) (c) Glucose (C6H12O6) (d) Ammonia (NH3)

Classify the following substances as strong electrolytes, weak electrolytes, or nonelectrolytes: (a) Sodium permanganate (NaMnO4) (b) Acetic acid (CH3COOH) (c) Methanol (CH3OH) (d) Calcium acetate [Ca(C2H3O2)2]

How many moles of solute particles are present in 1 L of each of the following aqueous solutions? (a) 0.3 M KBr (b) 0.065 M HNO3 (c) 10_4 M KHSO4 (d) 0.06 M ethanol (C2H5OH)

How many moles of solute particles are present in 1 mL of each of the following aqueous solutions? (a) 0.02 M CuSO4 (b) 0.004 M Ba(OH)2 (c) 0.08 M pyridine (C5H5N) (d) 0.05 M (NH4)2CO3

Which solution has the lower freezing point? (a) 11.0 g of CH3OH in 100. g of H2O or 22.0 g of CH3CH2OH in 200. g of H2O (b) 20.0 g of H2O in 1.00 kg of CH3OH or 20.0 g of CH3CH2OH in 1.00 kg of CH3OH

Which solution has the higher boiling point? (a) 38.0 g of C3H8O3 in 250. g of ethanol or 38.0 g of C2H6O2 in 250. g of ethanol (b) 15 g of C2H6O2 in 0.50 kg of H2O or 15 g of NaCl in 0.50 kg of H2O

Rank the following aqueous solutions in order of increasing (a) osmotic pressure; (b) boiling point; (c) freezing point; (d) vapor pressure at 50_C: (I) 0.100 m NaNO3 (II) 0.100 m glucose (III) 0.100 m CaCl2

Rank the following aqueous solutions in order of decreasing (a) osmotic pressure; (b) boiling point; (c) freezing point; (d) vapor pressure at 298 K: (I) 0.04 m urea [(NH2)2C O] (II) 0.01 m AgNO3 (III) 0.03 m CuSO4

Calculate the vapor pressure of a solution of 34.0 g of glycerol (C3H8O3) in 500.0 g of water at 25_C. The vapor pressure of water at 25_C is 23.76 torr. (Assume ideal behavior.)

Calculate the vapor pressure of a solution of 0.39 mol of cholesterol in 5.4 mol of toluene at 32_C. Pure toluene has a vapor pressure of 41 torr at 32_C. (Assume ideal behavior.)

What is the freezing point of 0.251 m urea in water?

What is the boiling point of 0.200 m lactose in water?

The boiling point of ethanol (C2H5OH) is 78.5_C. What is the boiling point of a solution of 6.4 g of vanillin _ 152.14 g/mol) in 50.0 g of ethanol (Kb of ethanol _ 1.22_C/m)?

The freezing point of benzene is 5.5_C. What is the freezing point of a solution of 5.00 g of naphthalene (C10H8) in 444 g of benzene (Kf of benzene _ 4.90_C/m)?

What is the minimum mass of ethylene glycol (C2H6O2) that must be dissolved in 14.5 kg of water to prevent the solution from freezing at _12.0_F? (Assume ideal behavior.)

What is the minimum mass of glycerol (C3H8O3) that must be dissolved in 11.0 mg of water to prevent the solution from freezing at _15_C? (Assume ideal behavior.)

Calculate the molality and vant Hoff factor (i) for the following aqueous solutions: (a) 1.00 mass % NaCl, freezing point __0.593_C (b) 0.500 mass % CH3COOH, freezing point __0.159_C

Calculate the molality and vant Hoff factor (i) for the following aqueous solutions: (a) 0.500 mass % KCl, freezing point __0.234_C (b) 1.00 mass % H2SO4, freezing point __0.423_C _ N

Wastewater discharged into a stream by a sugar refinery contains 3.55 g of sucrose (C12H22O11) per liter. A governmentindustry project is designed to test the feasibility of removing the sugar by reverse osmosis. What pressure must be applied to the apparatus at 20._C to produce pure water?

In a study designed to prepare new gasoline-resistant coatings, a polymer chemist dissolves 6.053 g of poly(vinyl alcohol) in enough water to make 100.0 mL of solution. At 25_C, the osmotic pressure of this solution is 0.272 atm. What is the molar mass of the polymer sample?

The U.S. Food and Drug Administration lists dichloromethane (CH2Cl2) and carbon tetrachloride (CCl4) among the many cancer-causing chlorinated organic compounds. What are the partial pressures of these substances in the vapor above a solution of 1.60 mol of CH2Cl2 and 1.10 mol of CCl4 at 23.5_C? The vapor pressures of pure CH2Cl2 and CCl4 at 23.5_C are 352 torr and 118 torr, respectively. (Assume ideal behavior.)

Is the fluid inside a bacterial cell considered a solution, a colloid, or both? Explain.

What type of colloid is each of the following? (a) Milk (b) Fog (c) Shaving cream

What is Brownian motion, and what causes it?

In a movie theater, you can see the beam of projected light. What phenomenon does this exemplify? Why does it occur?

Why dont soap micelles coagulate and form large globules? Is soap more effective in freshwater or in seawater? Why?

The three aqueous ionic solutions below have total volumes of 25 mL in A, 50. mL in B, and 100. mL in C. If each sphere represents 0.010 mol of ions, calculate: (a) the total molarity of ions for each solution; (b) the highest molarity of solute; (c) the lowest molality of solute (assuming the solution densities are equal); (d) the highest osmotic pressure (assuming ideal behavior).

An aqueous solution is 10.% glucose by mass (d _ 1.039 g/mL at 20_C). Calculate its freezing point, boiling point at 1 atm, and osmotic pressure.

Because zinc has nearly the same atomic radius as copper (d _ 8.95 g/cm3), zinc atoms substitute for some copper atoms in the many types of brass. Calculate the density of the brass with (a) 10.0 atom % Zn and (b) 38.0 atom % Zn.

Gold occurs in seawater at an average concentration of 1.1_10_2 ppb. How many liters of seawater must be processed to recover 1 troy ounce of gold, assuming 81.5% efficiency (d of seawater _ 1.025 g/mL; 1 troy ounce _ 31.1 g)?

Use atomic properties to explain why xenon is 11 times as soluble as helium in water at 0_C on a mole basis.

Which of the following best represents a molecular-scale view of an ionic compound in aqueous solution? Explain.

Four 0.50 m aqueous solutions are depicted below. Assume the solutions behave ideally: (a) Which has the highest boiling point? (b) Which has the lowest freezing point? (c) Can you determine which one has the highest osmotic pressure? Explain.

Thermal pollution from industrial wastewater causes the temperature of river or lake water to increase, which can affect fish survival as the concentration of dissolved O2 decreases. Use the following data to find the molarity of O2 at each temperature (assume the solution density is the same as water):

Pyridine (right) is an essential portion of many biologically active compounds, such as nicotine and vitamin B6. Like ammonia, it has a nitrogen with a lone pair, which makes it act as a weak base. Because it is miscible in a wide range of solvents, from water to benzene, pyridine is one of the most important bases and solvents in organic syntheses. Account for its solubility behavior in terms of intermolecular forces.

A chemist is studying small organic compounds for their potential use as an antifreeze. When 0.243 g of a compound is dissolved in 25.0 mL of water, the freezing point of the solution is _0.201_C. (a) Calculate the molar mass of the compound (d of water _ 1.00 g/mL). (b) Analysis shows that the compound is 53.31 mass % C and 11.18 mass % H, the remainder being O. Calculate the empirical and molecular formulas of the compound. (c) Draw a Lewis structure for a compound with this formula that forms H bonds and another for one that does not.

Air in a smoky bar contains 4.0_10_6 mol/L of CO. What mass of CO is inhaled by a bartender who respires at a rate of 11 L/min during an 8.0-h shift?

Is 50% by mass of methanol dissolved in ethanol different from 50% by mass of ethanol dissolved in methanol? Explain.

Three gaseous mixtures of N2 (blue), Cl2 (green), and Ne (purple) are depicted below. (a) Which has the smallest mole fraction of N2? (b) Which have the same mole fraction of Ne? (c) Rank all three in order of increasing mole fraction of Cl2.

A water treatment plant needs to attain a fluoride concentration of 4.50_10_5 M. (a) What mass of NaF must be added to a 5000.-L blending tank of water? (b) What mass per day of fluoride is ingested by a person who drinks 2.0 L of this water?

Answer each of the following briefly: (a) Why is cake alum [Al2(SO4)3] added during water purification? (b) Why is water that contains large amounts of Ca2_ and Mg2_ difficult to use for cleaning? (c) What is the meaning of reverse in reverse osmosis? (d) Why might a water treatment plant use ozone as a disinfectant instead of chlorine? (e) How does passing a saturated NaCl solution through a spent ion-exchange resin regenerate the resin?

Four U tubes each have distilled water in the right arm, a solution in the left arm, and a semipermeable membrane between arms. (a) If the solute is KCl, which solution is most concentrated? (b) If each solute is different but all the solutions have the same molarity, which contains the smallest number of dissolved ions?

_-Pinene (C10H16) and _-terpineol (C10H18O) are used in cosmetics to provide a fresh pine scent. At 367 K, the pure substances have vapor pressures of 100.3 torr and 9.8 torr, respectively. What is the composition of the vapor (in terms of mole fractions) above a solution containing equal masses of these compounds at 367 K? (Assume ideal behavior.)

Asolution of 1.50 g of solute dissolved in 25.0 mL of H2O at 25_C has a boiling point of 100.45_C. (a) What is the molar mass of the solute if it is a nonvolatile nonelectrolyte and the solution behaves ideally (d of H2O at 25_C _ 0.997 g/mL)? (b) Conductivity measurements show the solute to be ionic of general formula AB2 or A2B. What is the molar mass if the solution behaves ideally? (c) Analysis indicates an empirical formula of CaN2O6. Explain the difference between the actual formula mass and that calculated from the boiling point elevation. (d) Find the vant Hoff factor (i) for this solution.

A pharmaceutical preparation made with ethanol (C2H5OH) is contaminated with methanol (CH3OH). A sample of vapor above the liquid mixture contains a 97/1 mass ratio of C2H5OH to CH3OH. What is the mass ratio of these alcohols in the liquid? At the temperature of the liquid, the vapor pressures of C2H5OH and CH3OH are 60.5 torr and 126.0 torr, respectively.

Water treatment plants commonly use chlorination to destroy bacteria. A byproduct is chloroform (CHCl3), a suspected carcinogen, produced when HOCl, formed by reaction of Cl2 and water, reacts with dissolved organic matter. The United States, Canada, and the World Health Organization have set a limit of 100. ppb of CHCl3 in drinking water. Convert this concentration into molarity, molality, mole fraction, and mass percent.

A saturated Na2CO3 solution is prepared, and a small excess of solid is present (white pile in beaker). A seed crystal of Na2 14CO3 (14C is a radioactive isotope of 12C) is added (small red piece), and the radioactivity is measured over time. (a) Would you expect radioactivity in the solution? Explain. (b) Would you expect radioactivity in all the solid or just in the seed crystal? Explain.

A biochemical engineer isolates a bacterial gene fragment and dissolves a 10.0-mg sample in enough water to make 30.0 mL of solution. The osmotic pressure of the solution is 0.340 torr at 25_C. (a) What is the molar mass of the gene fragment? (b) If the solution density is 0.997 g/mL, how large is the freezing point depression for this solution (Kf of water _ 1.86_C/m)?

A river is contaminated with 0.65 mg/L of dichloroethylene (C2H2Cl2). What is the concentration (in ng/L) of dichloroethylene at 21_C in the air breathed by a person swimming in the river (kH for C2H2Cl2 in water is 0.033 mol/L_atm)?

At an air-water interface, fatty acids such as oleic acid lie in a one-molecule-thick layer (monolayer), with the heads in the water and the tails perpendicular in the air. When 2.50 mg of oleic acid is placed on a water surface, it forms a circular monolayer 38.6 cm in diameter. Find the surface area (in cm2) occupied by one molecule ( of oleic acid _ 283 g/mol).

A simple device used for estimating the concentration of total dissolved solids in an aqueous solution works by measuring the electrical conductivity of the solution. The method assumes that equal concentrations of different solids give approximately the same conductivity, and that the conductivity is proportional to concentration. The table below gives some actual electrical conductivities (in arbitrary units) for solutions of selected solids at the indicated concentrations (in ppm by mass): (a) How reliable are these measurements for estimating concentrations of dissolved solids? (b) For what types of substances might this method have a large error? Why? (c) Based on this method, an aqueous CaCl2 solution has a conductivity of 14.0 units. Calculate its mole fraction and molality.

Two beakers are placed in a closed container (left). One beaker contains water, the other a concentrated aqueous sugar solution. With time, the solution volume increases and the water volume decreases (right). Explain on the molecular level.

The release of volatile organic compounds into the atmosphere is regulated to limit ozone formation. In a laboratory simulation, 5% of the ethanol in a liquid detergent is released. Thus, a down-the-drain factor of 0.05 is used to estimate ethanol emissions from the detergent. The kH values for ethanol and 2-butoxyethanol (C4H9OCH2CH2OH) are 5_10_6 atm_m3/mol and 1.6_10_6 atm_m3/mol, respectively. (a) Estimate a downthe- drain factor for 2-butoxyethanol in the detergent. (b) What is the kH for ethanol in units of L_atm/mol? (c) Is this value consistent with a value given as 0.64 Pa_m3/mol?

Although other solvents are available, dichloromethane (CH2Cl2) is still often used to decaffeinate drinks because the solubility of caffeine in CH2Cl2 is 8.35 times that in water. (a) A100.0-mL sample of cola containing 10.0 mg of caffeine is extracted with 60.0 mL of CH2Cl2. What mass of caffeine remains in the aqueous phase? (b) A second identical cola sample is extracted with two successive 30.0-mL portions of CH2Cl2. What mass of caffeine remains in the aqueous phase after each extraction? (c) Which approach extracts more caffeine?

How do you prepare 250. g of 0.150 m aqueous NaHCO3?

Tartaric acid occurs in crystalline residues found in wine vats. It is used in baking powders and as an additive in foods. It contains 32.3% by mass carbon and 3.97% by mass hydrogen; the balance is oxygen. When 0.981 g of tartaric acid is dissolved in 11.23 g of water, the solution freezes at _1.26_C. Find the empirical and molecular formulas of tartaric acid.

Methanol (CH3OH) and ethanol (C2H5OH) are miscible because the major intermolecular force for each is hydrogen bonding. In some methanol-ethanol solutions, the mole fraction of methanol is higher, but the mass percent of ethanol is higher. What is the range of mole fraction of methanol for these solutions?

Asolution of 5.0 g of benzoic acid (C6H5COOH) in 100.0 g of carbon tetrachloride has a boiling point of 77.5_C. (a) Calculate the molar mass of benzoic acid in the solution. (b) Suggest a reason for the difference between the molar mass based on the formula and that found in part (a).

Derive a general equation that expresses the relationship between the molarity and the molality of a solution. Why are the numerical values of these two terms approximately equal for very dilute aqueous solutions?

A florist prepares a solution of nitrogen-phosphorus fertilizer by dissolving 5.66 g of NH4NO3 and 4.42 g of (NH4)3PO4 in enough water to make 20.0 L of solution. What are the molarities of NH4 _ and of PO4 3_ in the solution?

Suppose coal-fired power plants used water in scrubbers to remove SO2 from smokestack gases (see Chemical Connections, p. 256). (a) If the partial pressure of SO2 in the stack gases is 2.0_10_3 atm, what is the solubility of SO2 in the scrubber liquid (kH for SO2 in water is 1.23 mol/L_atm at 200._C)? (b) From your answer to part (a), why are basic solutions, such as limewater slurries [Ca(OH)2], used in scrubbers?

Urea is a white crystalline solid used as a fertilizer, in the pharmaceutical industry, and in the manufacture of certain polymer resins. Analysis of urea reveals that, by mass, it is 20.1% carbon, 6.7% hydrogen, 46.5% nitrogen and the balance oxygen. (a) Find the empirical formula of urea. (b) A 5.0 g/L solution of urea in water has an osmotic pressure of 2.04 atm, measured at 25_C. What is the molar mass and molecular formula of urea?

The total concentration of dissolved particles in blood is 0.30 M. An intravenous (IV) solution must be isotonic with blood, which means it must have the same concentration. (a) To relieve dehydration, a patient is given 100. mL/h of IV glucose (C6H12O6) for 2.5 h. What mass (g) of glucose did she receive? (b) If isotonic saline (NaCl) is used, what is the molarity of the solution? (c) If the patient is given 150. mL/h of IV saline for 1.5 h, how many grams of NaCl did she receive?

Deviations from Raoults law lead to the formation of azeotropes, constant boiling mixtures that cannot be separated by distillation, making industrial separations difficult. For components A and B, there is a positive deviation if the A-B attraction is less than A-A and B-B attractions (A and B reject each other), and a negative deviation if the A-B attraction is greater than A-A and B-B attractions. If the A-B attraction is nearly equal to the A-A and B-B attractions, the solution obeys Raoults law. Explain whether the behavior of each pair will be nearly ideal, have a positive deviation, or a negative deviation: (a) benzene (C6H6) and methanol; (b) water and ethyl acetate; (c) hexane and heptane; (d) methanol and water; (e) water and hydrochloric acid.

Acrylic acid (CH2 CHCOOH) is a monomer used to make superabsorbent polymers and various compounds for paint and adhesive production. At 1 atm, it boils at 141.5_C but is prone to polymerization. Its vapor pressure at 25_C is 4.1 mbar. What pressure (in mmHg) is needed to distill the pure acid at 65_C?

To effectively stop polymerization, certain inhibitors require the presence of a small amount of O2. At equilibrium with 1 atm of air, the concentration of O2 dissolved in the monomer acrylic acid (CH2 CHCOOH) is 1.64_10_3 M. (a) What is the kH (mol/L_atm) for O2 in acrylic acid? (b) If 0.005 atm of O2 is sufficient to stop polymerization, what is the molarity of O2? (c) What is the mole fraction? (d) What is the concentration in ppm? (Pure acrylic acid is 14.6 M; in air is 0.2095 atm.)

Volatile organic solvents have been implicated in adverse health effects of industrial workers. Greener methods are phasing them out (see the margin note, p. 505). Rank the solvents in Table 13.6 (p. 530) in terms of increasing volatility.

At ordinary temperatures, water is a poor solvent for organic substances. But at high pressure and above 200_C, water develops many properties of organic solvents. Find the minimum pressure needed to maintain water as a liquid at 200._C ( Hvap _ 40.7 kJ/mol at 100_C and 1.00 atm; assume it remains constant with temperature).

In ice-cream making, the ingredients are kept below 0.0_C in an ice-salt bath. (a) Assuming that NaCl dissolves completely and forms an ideal solution, what mass of it is needed to lower the melting point of 5.5 kg of ice to _5.0_C? (b) Given the same assumptions as in part (a), what mass of CaCl2 is needed?

Perfluorocarbons (PFCs), hydrocarbons with all the H replaced by F, have very weak cohesive forces. One unusual application shows a mouse surviving submerged in O2-saturated PFCs. (a) At 298 K, perfluorohexane (C6F14, _ 338 g/mol, d _ 1.674 g/mL) in equilibrium with 101,325 Pa of O2 has a _ PO2 N N mole fraction of O2 of 4.28_10_3. What is the kH in mol/L_atm? (b) According to one source, the kH for O2 in water at 25_C is 756.7 L_atm/mol. What is the solubility of O2 in water at 25_C in ppm? (c) Rank the kH values in descending order for O2 in water, ethanol, C6F14, and C6H14. Explain your ranking.

The solubility of N2 in blood is a serious problem for divers breathing compressed air (78% N2 by volume) at depths greater than 50 ft (see the margin note, p. 522). (a) What is the molarity of N2 in blood at 1.00 atm? (b) What is the molarity of N2 in blood at a depth of 50. ft? (c) Find the volume (in mL) of N2, measured at 25_C and 1.00 atm, released per liter of blood when a diver at a depth of 50. ft rises to the surface (kH for N2 in water at 25_C is 7.0_10_4 mol/L_atm and at 37_C is 6.2_10_4 mol/L_atm; assume d of water is 1.00 g/mL).

Figure 12.9B (p. 448) shows the phase changes of pure water. Consider how the diagram would change if air were present at 1 atm and dissolved in the water. (a) Would the three phases of water still attain equilibrium at some temperature? Explain. (b) In principle, would that temperature be higher, lower, or the same as the triple point for pure water? Explain. (c) Would ice sublime at a few degrees below the freezing point under this pressure? Explain. (d) Would the liquid have the same vapor pressure as that shown in Figure 12.9B at 100_C? At 120_C?

KNO3, KClO3, KCl, and NaCl are recrystallized as follows: Step 1. A saturated aqueous solution of the compound is prepared at 50_C. Step 2. The mixture is filtered to remove undissolved compound. Step 3. The filtrate is cooled to 0_C. Step 4. The crystals that form are filtered, dried, and weighed. (a) Which compound has the highest percent recovery and which the lowest (see Figure 13.21, p. 520)? (b) Starting with 100. g of each compound, how many grams of each can be recovered?

Eighty proof whiskey is 40% ethanol (C2H5OH) by volume. Aman has 7.0 L of blood and drinks 28 mL of the whiskey, of which 22% of the ethanol goes into his blood. (a) What concentration (in g/mL) of ethanol is in his blood (d of ethanol _ 0.789 g/mL)? (b) What volume (in mL) of whiskey would raise his blood alcohol level to 8.0_10_4 g/mL, the level at which a person is considered intoxicated?

Soft drinks are canned under 4 atm of CO2 and release CO2 when opened (see the margin note, p. 522). (a) How many moles of CO2 are dissolved in a 355-mL can of soda before it is opened? (b) After it has gone flat? (c) What volume (in L) would the released CO2 occupy at 1.00 atm and 25_C (kH for CO2 at 25_C is 3.3_10_2 mol/L_atm; in air is 3_10_4 atm)?

Gaseous O2 in equilibrium with O2 dissolved in water at 283 K is depicted at right. (a) Which scene below represents the system at 298 K? (b) Which scene represents the system when the pressure of O2 is increased by half?