Answer: Explain the following on the basis of the behavior

You are given two aqueous solutions containing different ionic solutes (Solution A and Solution B). What if you are told that Solution A has a greater concentration than Solution B by mass percent, but Solution B has a greater concentration than Solution A in terms of molality? Is this possible? If not, explain why not. If it is possible, provide example solutes for A and B, and justify your answer with calculations

You and a friend are studying for a chemistry exam. What if your friend says Exothermic processes are favored and the sign of the enthalpy change tells whether or not a process is endothermic or exothermic. Therefore, the sign of DHsoln tells us whether or not a solution will form. How would you explain to your friend that this conclusion is not correct? What part, if any, of what your friend says is correct?

Consider the model of osmotic pressure as shown in Fig. 17.15. What if both sides contained a different pure solvent, each with a different vapor pressure? What would the system look like at equilibrium? Assume the different solvent molecules are able to pass through the membrane.

Consider Fig. 17.8. According to the caption and picture, water is transferred from one beaker to another. a. Explain why this occurs. b. The explanation in the text uses terms such as vapor pressure and equilibrium. Explain what these terms have to do with the phenomenon. For example, what does the equilibrium involve? c. Does all the water end up in the second beaker? d. Is the water in the beaker containing the solute evaporating? If so, is the rate of evaporation increasing, decreasing, or staying constant? Draw pictures to illustrate your explanations.

Consider Fig. 17.8. Suppose that instead of having a nonvolatile solute in the solvent in one beaker, the two beakers have different volatile liquids. That is, suppose one beaker contains liquid A (Pvap 5 50 torr) and the other beaker contains liquid B (Pvap 5 100 torr). Explain what happens as time passes. How is this similar to the first case shown in the figure? How is it different?

Assume that you place a freshwater plant into a saltwater solution and examine it under a microscope. What happens to the plant cells? What if you placed a saltwater plant in pure water? Explain. Draw pictures to illustrate your explanations.

How does DHsoln relate to deviations from Raoults law? Explain.

You have read that adding NaCl to water can both increase its boiling point and decrease its freezing point. A friend of yours explains it to you like this: The ions prevent freezing by blocking the water molecules from joining together. The hydration of the ions also makes the water boil at a higher temperature. What do you say to your friend?

You drop an ice cube (made from pure water) into a saltwater solution at 08C. Explain what happens and why

Using the phase diagram for water and Raoults law, explain why salt is spread on the roads in winter (even when the temperature is below freezing).

You and your friend are each drinking cola from separate 2-L bottles. Both colas are equally carbonated. You are able to drink 1 L of cola, but your friend can drink only about half a liter. You each close the bottles, and place them in the refrigerator. The next day when you each go to get the colas, whose will be more carbonated and why?

Is molality or molarity dependent on temperature? Explain your answer. Why is molality, and not molarity, used in the equations describing freezing-point depression and boiling-point elevation?

If a solution shows positive deviations from Raoults law, would you expect it to have a higher or lower boiling point than if it were ideal? Explain

Consider a beaker of salt water sitting open in a room. Over time does the vapor pressure increase, decrease, or stay the same? Explain

The four most common ways to describe solution composition are mass percent, mole fraction, molarity, and molality. Define each of these solution composition terms. Why is molarity temperature-dependent, whereas the other three solution composition terms are temperature-independent?

Write equations showing the ions present after the following strong electrolytes are dissolved in water. a. HNO3 d. SrBr2 g. NH4NO3 b. Na2SO4 e. KClO4 h. CuSO4 c. Al(NO3)3 f. NH4Br i. NaOH

Calculate the sodium ion concentration when 70.0 mL of 3.0 M sodium carbonate is added to 30.0 mL of 1.0 M sodium bicarbonate

An aqueous antifreeze solution is 40.0% ethylene glycol (C2H6O2) by mass. The density of the solution is 1.05 g/cm3. Calculate the molality, molarity, and mole fraction of the ethylene glycol.

Common commercial acids and bases are aqueous solutions with the following properties: Density (g/cm3) Mass Percent of Solute Hydrochloric acid 1.19 38 Nitric acid 1.42 70. Sulfuric acid 1.84 95 Acetic acid 1.05 99 Ammonia 0.90 28 Calculate the molarity, molality, and mole fraction of each of these reagents.

A solution is prepared by mixing 50.0 mL of toluene (C6H5CH3, d 5 0.867 g/cm3) with 125 mL of benzene (C6H6, d 5 0.874 g/cm3). Assuming that the volumes add on mixing, calculate the mass percent, mole fraction, molality, and molarity of the toluene.

A bottle of wine contains 12.5% ethanol by volume. The density of ethanol (C2H5OH) is 0.789 g/cm3. Calculate the concentration of ethanol in wine in terms of mass percent and molality

A 1.37 M aqueous solution of citric acid (H3C6H5O7) has a density of 1.10 g/cm3. What are the mass percent, molality, and mole fraction of the citric acid?

Determine the molarity and mole fraction of a 1.00 m solution of acetone (CH3COCH3) dissolved in ethanol (C2H5OH). (Density of acetone 5 0.788 g/cm3; density of ethanol 5 0.789 g/cm3.) Assume that the final volume equals the sum of the volumes of acetone and ethanol

A solution of phosphoric acid was made by dissolving 10.0 g of H3PO4 in 100.00 mL of water. The resulting volume was 104 mL. Calculate the density, mole fraction, molarity, and molality of the solution. Assume water has a density of 1.00 g/cm3.

In a lab you need at least 100 mL of each of the following solutions. Explain how you would proceed by using the given information. a. 2.0 m KCl in water (density of H2O 5 1.00 g/cm3) b. 15% NaOH by mass in water c. 25% NaOH by mass in CH3OH (d 5 0.79 g/cm3) d. 0.10 mole fraction of C6H12O6 in water

A solution is prepared by mixing 25 mL pentane (C5H12, d 5 0.63 g/cm3) with 45 mL hexane (C6H14, d 5 0.66 g/cm3). Assuming that the volumes add on mixing, calculate the mass percent, mole fraction, molality, and molarity of the pentane.

Using KF as an example, write equations that refer to DHsoln and DHhyd. Lattice energy was defined in Chapter 13 as DH for the reaction K1(g) 1 F2(g) 8n KF(s). Show how you would utilize Hesss law to calculate DHsoln from DHhyd and DHLE for KF, where DHLE 5 lattice energy. DHsoln for KF, as for other soluble ionic compounds, is a relatively small number. How can this be since DHhyd and DHLE are relatively large negative numbers?

What does the axiom like dissolves like mean? There are four types of solutesolvent combinations: polar solutes in polar solvents, nonpolar solutes in polar solvents, and so on. For each type of solution, discuss the magnitude of DHsoln.

For each of the following solutesolvent combinations, state the sign and relative magnitudes for DH1, DH2, DH3, and DHsoln (as defined in Fig. 17.1 of the text). Explain your answers. H H H H H H O C C C H H O a. and H H O H H H H H H C O C b. and H H H H H H H H H H H H H H C C C C C C H H H H H H H H H H H H H H H H C C C C C C C c. and H H O H H H H H H H H H H H H H H H H C C C C C C C d

In order for sodium chloride to dissolve in water, a small amount of energy must be added during solution formation. This is not energetically favorable. Why is NaCl so soluble in water?

The high melting points of ionic solids indicate that a lot of energy must be supplied to separate the ions from one another. How is it possible that the ions can separate from one another when soluble ionic compounds are dissolved in water, often with essentially no temperature change?

The lattice energy* of NaI is 2686 kJ/mol, and the enthalpy of hydration is 2694 kJ/mol. Calculate the enthalpy of solution per mole of solid NaI. Describe the process to which this enthalpy change applies.

a. Use the following data to calculate the enthalpy of hydration for calcium chloride and calcium iodide. Lattice Energy* DHsoln CaCl2(s) 22247 kJ/mol 246 kJ/mol CaI2(s) 22059 kJ/mol 2104 kJ/mol b. Based on your answers to part a, which ion, Cl2 or I2, is more strongly attracted to water?

Although Al(OH)3 is insoluble in water, NaOH is very soluble. Explain this difference in terms of lattice energies

Which ion in each of the following pairs would you expect to be more strongly hydrated? Why? a. Na1 or Mg21 d. F2 or Br2 b. Mg21 or Be21 e. Cl2 or ClO4 2 c. Fe21 or Fe31 f. ClO4 2 or SO4 22

For each of the following pairs, predict which substance would be more soluble in water. CH3CN CH3CH3 NH3 PH3 or or or a. b. c. CH3COOH O B O B CH3OCOOCH3

Which solvent, water or carbon tetrachloride, would you choose to dissolve each of the following? a. KrF2 e. MgF2 b. SF2 f. CH2O c. SO2 g. CH2PCH2 d. CO2

Rationalize the trend in water solubility for the following simple alcohols. Alcohol Solubility (g/100 g H2O at 208C) Methanol, CH3OH Soluble in all proportions Ethanol, CH3CH2OH Soluble in all proportions Propanol, CH3CH2CH2OH Soluble in all proportions Butanol, CH3(CH2)2CH2OH 8.14 Pentanol, CH3(CH2)3CH2OH 2.62 Hexanol, CH3(CH2)4CH2OH 0.59 Heptanol, CH3(CH2)5CH2OH 0.09

In the flushing and cleaning of columns used in liquid chromatography, a series of solvents is used. Hexane (C6H14), chloroform (CHCl3), methanol (CH3OH), and water are passed through the column in that order. Rationalize the order in terms of intermolecular forces and the mutual solubility (miscibility) of the solvents.

Structure, pressure, and temperature all have an effect on solubility. Discuss each of their effects. What is Henrys law? Why does Henrys law not work for HCl(g)? What do the terms hydrophobic and hydrophilic mean?

O2(g) obeys Henrys law in water but not in blood (an aqueous solution). Why?

The solubility of nitrogen in water is 8.21 3 1024 mol/L at 08C when the N2 pressure above water is 0.790 atm. Calculate the Henrys law constant for N2 in units of L atm/mol for Henrys law in the form P 5 kC, where C is the gas concentration in mol/L. Calculate the solubility of N2 in water when the partial pressure of nitrogen above water is 1.10 atm at 08C.

In Exercise 118 in Chapter 5, the pressure of CO2 in a bottle of sparkling wine was calculated assuming that the CO2 was insoluble in water. This was an incorrect assumption. Redo this problem by assuming that CO2 obeys Henrys law. Use the data given in that problem to calculate the partial pressure of CO2 in the gas phase and the solubility of CO2 in the wine at 258C. The Henrys law constant for CO2 is 32 L atm/mol at 258C with Henrys law in the form P 5 kC, where C is the concentration of the gas in mol/L.

Rationalize the temperature dependence of the solubility of a gas in terms of the kinetic molecular theory

Glycerin (C3H8O3) is a nonvolatile liquid. What is the vapor pressure of a solution made by adding 164 g of glycerin to 338 mL of H2O at 39.88C? The vapor pressure of pure water at 39.88C is 54.74 torr and its density is 0.992 g/cm3

The vapor pressure of a solution containing 53.6 g glycerin (C3H8O3) in 133.7 g ethanol (C2H5OH) is 113 torr at 408C. Calculate the vapor pressure of pure ethanol at 408C assuming that glycerin is a nonvolatile, nonelectrolyte solute in ethanol.

Which of the following will have the lowest total vapor pressure at 258C? Which has the highest vapor pressure at 258C? At 258C, the vapor pressure of pure water is 23.8 torr. a. pure water b. a solution of glucose in water with xglucose 5 0.01 c. a solution of sodium chloride in water with xNaCl 5 0.01 d. a solution of methanol in water with xCH3OH 5 0.2 (At 258C, the vapor pressure of pure methanol is 143 torr.)

The normal boiling point of diethyl ether is 34.58C. A solution containing a nonvolatile solute dissolved in diethyl ether has a vapor pressure of 698 torr at 34.58C. What is the mole fraction of diethyl ether in this solution?

A solution is prepared by mixing 0.0300 mole of CH2Cl2 and 0.0500 mole of CH2Br2 at 258C. Assuming the solution is ideal, calculate the composition of the vapor (in terms of mole fractions) at 258C. At 258C the vapor pressures of pure CH2Cl2 and pure CH2Br2 are 133 and 11.4 torr, respectively.

At a certain temperature, the vapor pressure of pure benzene (C6H6) is 0.930 atm. A solution was prepared by dissolving 10.0 g of a nondissociating, nonvolatile solute in 78.11 g of benzene at that temperature. The vapor pressure of the solution was found to be 0.900 atm. Assuming that the solution behaves ideally, determine the molar mass of the solute

At 258C the vapor in equilibrium with a solution containing carbon disulfide and acetonitrile has a total pressure of 263 torr and is 85.5 mole percent carbon disulfide. What is the mole fraction of carbon disulfide in the solution? At 258C the vapor pressure of carbon disulfide is 375 torr. Assume that the solution and the vapor exhibit ideal behavior

Pentane (C5H12) and hexane (C6H14) combine to form an ideal solution. At 258C the vapor pressures of pentane and hexane are 511 and 150. torr, respectively. A solution is prepared by mixing 25 mL of pentane (density 5 0.63 g/mL) with 45 mL of hexane (density 5 0.66 g/mL). a. What is the vapor pressure of this solution? b. What is the mole fraction of pentane in the vapor that is in equilibrium with this solution?

Benzene and toluene form ideal solutions. Consider a solution of benzene and toluene prepared at 258C. Assuming that the mole fractions of benzene and toluene in the vapor phase are equal, calculate the composition of the solution. At 258C the vapor pressures of benzene and toluene are 95 and 28 torr, respectively

A solution is made by mixing 50.0 g of acetone (CH3COCH3) and 50.0 g of methanol (CH3OH). What is the vapor pressure of this solution at 258C? What is the composition of the vapor expressed as a mole fraction? Assume ideal solution and gas behavior. (At 258C the vapor pressures of pure acetone and pure methanol are 271 and 143 torr, respectively.) The actual vapor pressure of this solution is 161 torr. Explain any discrepancies.

What is the composition of a methanol (CH3OH) propanol (CH3CH2CH2OH) solution that has a vapor pressure of 174 torr at 408C? At 408C the vapor pressures of pure methanol and pure propanol are 303 and 44.6 torr, respectively. Assume that the solution exhibits ideal behavior.

Match the vapor pressure diagrams with the solute solvent combinations and explain your answers. Vapor pressure B (a) (b) (c) A A A B B Vapor pressure of solution Vapor pressure of solution Vapor pressure of solution Partial pressure B Partial pressure A H H H H H H O C C C H H O H H O H H O H H H H H H C O C H H H H H H H H H H H H H H

The vapor pressures of several solutions of water propanol (CH3CH2CH2OH) were determined at various compositions, with the following data collected at 458C: xH2O Vapor Pressure (torr) 0 74.0 0.15 77.3 0.37 80.2 0.54 81.6 0.69 80.6 0.83 78.2 1.00 71.9 a. Are solutions of water and propanol ideal? Explain. b. Predict the sign of DHsoln for waterpropanol solutions. c. Are the interactive forces between propanol and water molecules weaker than, stronger than, or equal to the interactive forces between the pure substances? Explain. d. Which of the solutions in the table would have the lowest normal boiling point?

When pure methanol is mixed with water, the solution gets warmer to the touch. Would you expect this solution to be ideal? Explain.

The two beakers in the sealed container illustrated below contain pure water and an aqueous solution of a volatile solute. Water Aqueous solution If the solute is less volatile than water, explain what will happen to the volumes in the two containers as time passes.

The following plot shows the vapor pressure of various solutions of components A and B at some temperature. 0 PA 0 PB 0 1 Mole fraction B Vapor pressure (torr) Which of the following statements is false concerning solutions of A and B? a. The solutions exhibit negative deviations from Raoults law. b. DHsoln for the solutions should be exothermic. c. The intermolecular forces are stronger in solution than in either pure A or pure B. d. Pure liquid B is more volatile than pure liquid A. e. The solution with xB 5 0.6 will have a lower boiling point than either pure A or pure B.

Vapor-pressure lowering is a colligative property, as are freezing-point depression and boiling-point elevation. What is a colligative property? Why is the freezing point depressed for a solution as compared to the pure solvent? Why is the boiling point elevated for a solution as compared to the pure solvent?

Osmotic pressure is also a colligative property. What is osmotic pressure? Molarity units are used in the equation to calculate osmotic pressure. When does the molarity of a solution approximately equal the molality of the solution?

Is the following statement true or false? Explain your answer. When determining the molar mass of a solute using boiling-point or freezing-point data, camphor would be the best solvent choice of all of the solvents listed in Table 17.5.

A solution is prepared by dissolving 27.0 g of urea [(NH2)2CO], in 150.0 g of water. Calculate the boiling point of the solution. Urea is a nonelectrolyte.

What mass of glycerin (C3H8O3), a nonelectrolyte, must be dissolved in 200.0 g of water to give a solution with a freezing point of 21.508C?

Calculate the freezing point and boiling point of an antifreeze solution that is 50.0% by mass ethylene glycol (HOCH2CH2OH) in water. Ethylene glycol is a nonelectrolyte

The freezing point of t-butanol is 25.508C and Kf is 9.18C kg/mol. Usually t-butanol absorbs water on exposure to air. If the freezing point of a 10.0-g sample of t-butanol is 24.598C, how many grams of water are present in the sample?

How would you prepare 1.0 L of an aqueous solution of sucrose (C12H22O11) having an osmotic pressure of 15 atm at a temperature of 228C? Sucrose is a nonelectrolyte

If the human eye has an osmotic pressure of 8.00 atm at 258C, what concentration of solute particles in water will provide an isotonic eyedrop solution (a solution with equal osmotic pressure)?

Reserpine is a natural product isolated from the roots of the shrub Rauwolfia serpentina. It was first synthesized in 1956 by Nobel Prize winner R. B. Woodward. It is used as a tranquilizer and sedative. When 1.00 g reserpine is dissolved in 25.0 g camphor, the freezing-point depression is 2.63C (Kf for camphor is 40.8C ? kg/mol). Calculate the molality of the solution and the molar mass of reserpine

An aqueous solution of 10.00 g of catalase, an enzyme found in the liver, has a volume of 1.00 L at 278C. The solutions osmotic pressure at 278C is found to be 0.745 torr. Calculate the molar mass of catalase.

A solution contains 3.75 g of a nonvolatile pure hydrocarbon in 95 g acetone. The boiling points of pure acetone and the solution are 55.958C and 56.508C, respectively. The molal boiling-point constant of acetone is 1.718C ? kg/mol. What is the molar mass of the hydrocarbon?

What volume of ethylene glycol (C2H6O2), a nonelectrolyte, must be added to 15.0 L of water to produce an antifreeze solution with a freezing point of 230.08C? What is the boiling point of this solution? (The density of ethylene glycol is 1.11 g/cm3, and the density of water is 1.00 g/cm3.)

a. Calculate the freezing-point depression and osmotic pressure at 258C of an aqueous solution containing 1.0 g/L of a protein (molar mass 5 9.0 3 104 g/mol) if the density of the solution is 1.0 g/cm3. b. Considering your answer to part a, which colligative property, freezing-point depression or osmotic pressure, would be better used to determine the molar masses of large molecules? Explain.

Erythrocytes are red blood cells containing hemoglobin. In a saline solution they shrivel when the salt concentration is high and swell when the salt concentration is low. In a 258C aqueous solution of NaCl, whose freezing point is 20.4068C, erythrocytes neither swell nor shrink. If we want to calculate the osmotic pressure of the solution inside the erythrocytes under these conditions, what do we need to assume? Why? Estimate how good (or poor) of an assumption this is. Make this assumption and calculate the osmotic pressure of the solution inside the erythrocytes

If the fluid inside a tree is about 0.1 M more concentrated in solute than the groundwater that bathes the roots, how high will a column of fluid rise in the tree at 258C? Assume that the density of the fluid is 1.0 g/cm3. (The density of mercury is 13.6 g/cm3.)

A 1.60-g sample of a mixture of naphthalene (C10H8) and anthracene (C14H10) is dissolved in 20.0 g of benzene (C6H6). The freezing point of the solution is 2.818C. What is the composition of the sample mixture in terms of mass percent? The freezing point of benzene is 5.518C, and Kf is 5.128C kg/mol.

Before refrigeration became common, many foods were preserved by salting them heavily. Fruits were preserved by mixing them with a large amount of sugar (fruit preserves). How do salt and sugar act as preservatives?

Distinguish between a strong electrolyte, a weak electrolyte, and a nonelectrolyte. How can colligative properties be used to distinguish between them?

What is ion pairing?

Calculate the freezing point and the boiling point of each of the following solutions. (Assume complete dissociation.) a. 5.0 g NaCl in 25 g H2O b. 2.0 g Al(NO3)3 in 15 g H2O

A solution of sodium chloride in water has a vapor pressure of 19.6 torr at 258C. What is the mole fraction of NaCl in this solution? What would be the vapor pressure of this solution at 458C? The vapor pressure of pure water is 23.8 torr at 258C and 71.9 torr at 458C.

Consider an aqueous solution containing sodium chloride that has a density of 1.01 g/mL. Assume that the solution behaves ideally. The freezing point of this solution at 1.00 atm is 21.288C. Calculate the percent composition of this solution (by mass).

Consider the following solutions: 0.010 m Na3PO4 in water 0.020 m CaBr2 in water 0.020 m KCl in water 0.020 m HF in water (HF is a weak acid.) a. Assuming complete dissociation of the soluble salts, which solution(s) would have the same boiling point as 0.040 m C6H12O6 in water? (C6H12O6 is a nonelectrolyte.) b. Which solution would have the highest vapor pressure at 288C? c. Which solution would have the largest freezingpoint depression?

From the following: pure water solution of C6H12O6 (x 5 0.01) in water solution of NaCl (x 5 0.01) in water solution of CaCl2 (x 5 0.01) in water choose the one with the following: a. highest freezing point b. lowest freezing point c. highest boiling point d. lowest boiling point e. highest osmotic pressure

Determine the vant Hoff factor for the following ionic solute dissolved in water.

Consider the following representations of an ionic solute in water. Which flask contains MgSO4, and which flask contains NaCl? How can you tell?

The freezing-point depression of a 0.091 m solution of CsCl is 0.3208C. The freezing-point depression of a 0.091 m solution of CaCl2 is 0.4408C. In which solution does ion association appear to be greater? Explain.

Consider the following: Semipermeable membrane Pure solvent Solution What would happen to the level of liquid in the two arms if the semipermeable membrane separating the two liquids were permeable to a. H2O (the solvent) only? b. H2O and solute?

A water desalination plant is set up near a salt marsh containing water that is 0.10 M NaCl. Calculate the minimum pressure that must be applied at 20.8C to purify the water by reverse osmosis. Assume that NaCl is completely dissociated.

Calculate the freezing point and the boiling point of each of the following aqueous solutions. (Assume complete dissociation.) a. 0.050 m MgCl2 b. 0.050 m FeCl3

Calculate the freezing point and the boiling point of each of the following solutions using the observed vant Hoff factors in Table 17.6. a. 0.050 m MgCl2 b. 0.050 m FeCl3

Use the data in the following table for three different aqueous solutions of CaCl2 to calculate the apparent value of the vant Hoff factor. Molality Freezing-Point Depression (8C) 0.0225 0.110 0.0910 0.440 0.278 1.330

A 0.500-g sample of a compound is dissolved in enough water to form 100.0 mL of solution. This solution has an osmotic pressure of 2.50 atm at 258C. If each molecule of the solute dissociates into two particles (in this solvent), what is the molar mass of this solute?

In the winter of 1994, record low temperatures were registered throughout the United States. For example, in Champaign, Illinois, a record low of 2298F was registered. At this temperature can salting icy roads with CaCl2 be effective in melting the ice? a. Assume that i 5 3.00 for CaCl2. b. Assume the average value of i from Exercise 90. (The solubility of CaCl2 in cold water is 74.5 g per 100.0 g of water.)

The Tyndall effect is often used to distinguish between a colloidal suspension and a true solution. Explain

Detergent molecules can stabilize the emulsion of oil in water as well as remove dirt from soiled clothes. A typical detergent is sodium dodecylsulfate (SDS), which has a formula of CH3(CH2)10CH2SO4 2Na1. In aqueous solution, SDS suspends oil or dirt by forming small aggregates of detergent anions called micelles. Propose a structure for micelles.

The destruction of a colloid is done through a process called coagulation. What is coagulation?

What stabilizes a colloidal suspension? Explain why adding heat or adding an electrolyte can cause the suspended particles to settle out.

The term proof is defined as twice the percent by volume of pure ethanol in solution. Thus a solution that is 95% (by volume) ethanol is 190 proof. What is the molarity of ethanol in a 92-proof ethanolwater solution? Assume the density of ethanol (C2H5OH) is 0.79 g/cm3 and the density of water is 1.0 g/cm3

Patients undergoing an upper gastrointestinal tract laboratory test are typically given an X-ray contrast agent that aids with the radiologic imaging of the anatomy. One such contrast agent is sodium diatrizoate, a nonvolatile water-soluble compound. A 0.378-m solution is prepared by dissolving 38.4 g of sodium diatrizoate (NaDTZ) in 1.60 3 102 mL of water at 31.28C (the density of water at 31.28C is 0.995 g/mL). What is the molar mass of sodium diatrizoate? What is the vapor pressure of this solution if the vapor pressure of pure water at 31.28C is 34.1 torr?

The freezing point of an aqueous solution is 22.798C. a. Determine the boiling point of this solution. b. Determine the vapor pressure (in mm Hg) of this solution at 258C (the vapor pressure of pure water at 258C is 23.76 mm Hg). c. Explain any assumptions you make in solving parts a and b.

An aqueous solution containing 0.250 mole of Q, a strong electrolyte, in 5.00 3 102 g of water freezes at 22.798C. What is the vant Hoff factor for Q? The molal freezing-point depression constant for water is 1.868C kg/mol. What is the formula of Q if it is 38.68% chlorine by mass and there are twice as many anions as cations in one formula unit of Q?

The solubility of benzoic acid, O O B C H O O is 0.34 g/100 mL in water at 258C and 10.0 g/100 mL in benzene (C6H6) at 258C. Rationalize this solubility behavior. For a 1.0-m solution of benzoic acid in benzene, would the measured freezing-point depression be equal to, greater than, or less than 5.128C? (Kf 5 5.128C kg/ mol for benzene.)

Would benzoic acid be more or less soluble in a 0.1-M NaOH solution than it is in water?

In a coffee-cup calorimeter, 1.60 g of NH4NO3 was mixed with 75.0 g of water at an initial temperature of 25.008C. After dissolution of the salt, the final temperature of the calorimeter contents was 23.348C. a. Assuming the solution has a heat capacity of 4.18 J 8C21 g21, and assuming no heat loss to the calorimeter, calculate the enthalpy of solution (DHsoln) for the dissolution of NH4NO3 in units of kJ/mol. b. If the enthalpy of hydration for NH4NO3 is 2630. kJ/mol, calculate the lattice energy of NH4NO3.

Creatinine, C4H7N3O, is a by-product of muscle metabolism, and creatinine levels in the body are known to be a fairly reliable indicator of kidney function. The normal level of creatinine in the blood for adults is approximately 1.0 mg per deciliter (dL) of blood. If the density of blood is 1.025 g/mL, calculate the molality of a normal creatinine level in a 10.0-mL blood sample. What is the osmotic pressure of this solution at 25.08C?

In the vapor over a pentanehexane solution at 258C, the mole fraction of pentane is equal to 0.15. What is the mole fraction of pentane in the solution? (See Exercise 49 for the vapor pressures of the pure liquids.)

Explain the following on the basis of the behavior of atoms and/or ions. a. Cooking with hot water is faster in a pressure cooker than in an open pan. b. Salt is used on icy roads. c. Melted sea ice from the Arctic Ocean produces fresh water. d. CO2(s) (dry ice) does not have a normal boiling point under normal atmospheric conditions, even though CO2 is a liquid in fire extinguishers.

Which of the following statements is(are) true? Correct the false statements. a. The vapor pressure of a solution is directly related to the mole fraction of solute. b. When a solute is added to water, the water in solution has a lower vapor pressure than that of pure ice at 08C. c. Colligative properties depend only on the identity of the solute and not on the number of solute particles present. d. When sugar is added to water, the boiling point of the solution increases above 1008C because sugar has a higher boiling point than water.

Thyroxine, an important hormone that controls the rate of metabolism in the body, can be isolated from the thyroid gland. When 0.455 g thyroxine is dissolved in 10.0 g benzene, the freezing point of the solution is depressed by 0.3008C. What is the molar mass of thyroxine? See Table 17.5.

Anthraquinone contains only carbon, hydrogen, and oxygen. When 4.80 mg of anthraquinone is burned, 14.2 mg of CO2 and 1.65 mg of H2O are produced. The freezing point of camphor is lowered by 22.38C when 1.32 g of anthraquinone is dissolved in 11.4 g of camphor. Determine the empirical and molecular formulas of anthraquinone.

An unknown compound contains only carbon, hydrogen, and oxygen. Combustion analysis of the compound gives mass percents of 31.57% C and 5.30% H. The molar mass is determined by measuring the freezingpoint depression of an aqueous solution. A freezing point of 25.208C is recorded for a solution made by dissolving 10.56 g of the compound in 25.0 g of water. Determine the empirical formula, molar mass, and molecular formula of the compound. Assume that the compound is a nonelectrolyte.

A forensic chemist is given a white solid that is suspected of being pure cocaine (C17H21NO4, molar mass 5 303.36 g/mol). She dissolves 1.22 6 0.01 g of the solid in 15.60 6 0.01 g of benzene. The freezing point is lowered by 1.32 6 0.048C. a. What is the molar mass of the substance? Assuming that the percentage of uncertainty in the calculated molar mass is the same as the percentage of uncertainty in the temperature change, calculate the uncertainty in the molar mass. b. Could the chemist unequivocally state that the substance is cocaine? For example, is the uncertainty small enough to distinguish cocaine from codeine (C18H21NO3, molar mass 5 299.37)? c. Assuming that the absolute uncertainties in the measurements of temperature and mass remain unchanged, how could the chemist improve the precision of her results?

You add an excess of solid MX in 250 g of water. You measure the freezing point and find it to be 20.0288C. What is the Ksp of the solid?

A solution saturated with a salt of the type M3X2 has an osmotic pressure of 2.64 3 1022 atm at 258C. Calculate the Ksp value for the salt, assuming ideal behavior

You take 20.0 g of a sucrose (C12H22O11) and NaCl mixture and dissolve it in 1.00 L of water. The freezing point of this solution is found to be 20.4268C. Assuming ideal behavior, calculate the mass percent composition of the original mixture and the mole fraction of sucrose in the original mixture

Formic acid (HCO2H) is a monoprotic acid that ionizes only partially in aqueous solutions. A 0.10-M formic acid solution is 4.2% ionized. Assuming that the molarity and molality of the solution are the same, calculate the freezing point and the boiling point of 0.10 M formic acid.

A 0.100-g sample of the weak acid HA (molar mass 5 100.0 g/mol) is dissolved in 500.0 g of water. The freezing point of the resulting solution is 20.00568C. Calculate the value of Ka for this acid. Assume molarity equals molality in this solution.

A solid mixture contains MgCl2 (molar mass 5 95.218 g/mol) and NaCl (molar mass 5 58.443 g/mol). When 0.5000 g of this solid is dissolved in enough water to form 1.000 L of solution, the osmotic pressure at 25.08C is observed to be 0.3950 atm. What is the mass percent of MgCl2 in the solid? (Assume ideal behavior for the solution.)

Some nonelectrolyte solute (molar mass 5 142 g/mol) was dissolved in 150. mL of a solvent (density 5 0.879 g/cm3). The elevated boiling point of the solution was 355.4 K. What mass of solute was dissolved in the solvent? For the solvent, the enthalpy of vaporization is 33.90 kJ/mol, the entropy of vaporization is 95.95 J K21 mol21, and the boiling-point elevation constant is 2.5 K kg/mol.

Some nonelectrolyte solute (molar mass 5 142 g/mol) was dissolved in 150. mL of a solvent (density 5 0.879 g/cm3). The elevated boiling point of the solution was 355.4 K. What mass of solute was dissolved in the solvent? For the solvent, the enthalpy of vaporization is 33.90 kJ/mol, the entropy of vaporization is 95.95 J K21 mol21, and the boiling-point elevation constant is 2.5 K kg/mol.

The lattice energy of NaCl is 2786 kJ/mol, and the enthalpy of hydration of 1 mole of gaseous Na1 and 1 mole of gaseous Cl2 ions is 2783 kJ/mol. Calculate the enthalpy of solution per mole of solid NaCl.

For each of the following pairs, predict which substance is more soluble in water. a. CH3NH2 or NH3 b. CH3CN or CH3OCH3 c. CH3CH2OH or CH3CH2CH3 d. CH3OH or CH3CH2OH e. (CH3)3CCH2OH or CH3(CH2)6OH f. CH3OCH3 or CH3CO2H

The normal boiling point of methanol is 64.78C. A solution containing a nonvolatile solute dissolved in methanol has a vapor pressure of 556.0 torr at 64.78C. What is the mole fraction of methanol in this solution?

A solution is prepared by mixing 1.000 mole of methanol (CH3OH) and 3.18 moles of propanol (CH3CH2CH2OH). What is the composition of the vapor (in mole fractions) at 408C? At 408C, the vapor pressure of pure methanol is 303 torr, and the vapor pressure of pure propanol is 44.6 torr.

The molar mass of a nonelectrolyte is 58.0 g/mol. Determine the boiling point of a solution containing 35.0 g of this compound and 600.0 g of water. The barometric pressure during the experiment was such that the boiling point of pure water was 99.7258C

A 4.7 3 1022 mg sample of a protein is dissolved in water to make 0.25 mL of solution. The osmotic pressure of the solution is 0.56 torr at 258C. What is the molar mass of the protein

A solid consists of a mixture of NaNO3 and Mg(NO3)2. When 6.50 g of the solid is dissolved in 50.0 g of water, the freezing point of the solution is lowered by 5.238C. What is the composition by mass of the solid mixture?

Carbon tetrachloride (CCl4) and benzene (C6H6) form ideal solutions. Consider an equimolar solution of CCl4 and C6H6 at 258C. The vapor above the solution is collected and condensed. Using the following data, determine the composition in mole fraction of the condensed vapor. Substance DG8f C6H6(l) 124.50 kJ/mol C6H6(g) 129.66 kJ/mol CCl4(l) 265.21 kJ/mol CCl4(g) 260.59 kJ/mol

Liquid A has vapor pressure x, and liquid B has vapor pressure y. What is the mole fraction of the liquid mixture if the vapor above the solution is 30.% A by moles? 50.% A? 80.% A? (Calculate in terms of x and y.) What is the mole fraction of the vapor above the solution if the liquid mixture is 30.% A by moles? 50.% A? 80.% A? (Calculate in terms of x and y.)