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chemistry
physical chemistry
Chemical Principles 7th edition Steven S. Zumdahl, Donald J. DeCoste - Solutions
From the density of cesium chloride (3.97 g/cm3), calculate the distance between the centers of adjacent Cs+ and Cl- ions in the solid. Compare this value with the expected distance based on the sizes of the ions (Fig. 13.8). The ionic radius of Cs+ is 169 pm.Figure 13.8
A given sample of wüstite has the formula Fe0.950O1.00. Calculate the fraction of iron ions present as Fe3+. What fraction of the sites normally occupied by Fe2+ must be vacant in this solid?
Use the relative ionic radii in Fig. 13.8 to predict the structures expected for CsBr and KF. Do these predictions agree with observed structures? The ionic radius of Cs+ is 169 pm.Figure 13.8
MnO has either the NaCl type structure or the CsCl type structure. The edge length of the MnO unit cell is 4.47 × 10–8 cm, and the density of MnO is 5.28 g/cm3. a. Does MnO crystallize in the NaCl type or the CsCl type structure? b. Assuming that the ionic radius of oxygen is 140 pm, estimate
Superalloys have been made of nickel and aluminum. The alloy owes its strength to the formation of an ordered phase, called the gamma-prime phase, in which Al atoms are at the corners of a cubic unit cell and Ni atoms are at the face centers. What is the composition (relative numbers of atoms) for
The memory metal, nitinol, is an alloy of nickel and titanium. It is called a memory metal because after being deformed, a piece of nitinol wire will return to its original shape. (See Chem. Matters, October 1993, pp. 4–7.) The structure of nitinol consists of a simple cubic array of Ni atoms and
Predict which substance in each of the following pairs would have the greater intermolecular forces. a. CO2 or OCS b. SeO2 or SO2 c. CH3CH2CH2NH2 or H2NCH2CH2NH2 d. CH3CH3 or H2CO e. CH3OH or H2CO
A mineral crystallizes in a cubic closest packed array of oxygen ions with aluminum ions in some of the octahedral holes and magnesium ions in some of the tetrahedral holes. Deduce the formula of this mineral, and predict the fraction of octahedral holes and tetrahedral holes that are filled by the
Perovskite is a mineral containing calcium, titanium, and oxygen. The following diagrams represent the unit cell.a. What is the formula of perovskite? b. An alternative way of drawing the unit cell of perovskite has calcium at the center of each cubic unit cell. What are the positions of the
Materials containing the elements Y, Ba, Cu, and O that are superconductors (electrical resistance equals zero) at temperatures above that of liquid nitrogen were recently discovered. The structures of these materials are based on the perovskite structure. Were they to have the ideal perovskite
Define each of the following. a. Evaporation b. Condensation c. Sublimation d. Boiling e. Melting f. Enthalpy of vaporization g. Enthalpy of fusion h. Heating curve
How does each of the following affect the rate of evaporation of a liquid in an open dish? a. Intermolecular forces b. Temperature c. Surface area
Consider the following vapor pressure versus temperature plot for three different substances A, B, and C.If the three substances are CH4, SiH4, and NH3, match each curve to the correct substance.
A plot of ln(Pvap) versus 1/T (K) is linear with a negative slope. Why is this the case?
In Breckenridge, Colorado, the typical atmospheric pressure is 520 torr. What is the boiling point of water (ΔHvap = 40.7 kJ/ mol) in Breckenridge? What pressure would have to be applied to steam at 350oC to condense the steam to liquid water?
Carbon tetrachloride (CCl4) has a vapor pressure of 213 torr at 40oC and 836 torr at 80oC. What is the normal boiling point of CCl4?
The normal boiling point for acetone is 56.5oC. At an elevation of 5300 ft, the atmospheric pressure is 630 torr. What would be the boiling point of acetone (ΔHvap = 32.0 kJ/mol) at this elevation? What would be the vapor pressure of acetone at 25.0oC at this elevation?
In each of the following groups of substances, pick the one that has the given property. Justify your answer.a. Highest boiling point: HBr, Kr, or Cl2b. Highest freezing point: H2O, NaCl, or HFc. Lowest vapor pressure at 25oC: Cl2, Br2, or I2d. Lowest freezing point: N2, CO, or CO2e. Lowest boiling
Plot the following data, and from the graph determine ÎHvap for magnesium and lithium. In which metal is the bonding stronger?
From the following data for liquid nitric acid, determine its heat of vaporization and normal boiling point.
A substance has the following properties:Sketch a heating curve for the substance, starting at 250oC.
Use the heatingcooling curve below to answer the following questions.a. What is the freezing point of the liquid? b. What is the boiling point of the liquid? c. Which is greater, the heat of fusion or the heat of vaporization? Explain each term, and explain how the
How much energy does it take to convert 0.500 kg of ice at 220oC to steam at 250oC? Specific heat capacities: ice, 2.1 J g21 8C21; liquid, 4.2 Jg-1oC-1; steam, 2.0 Jg-1oC-1; ΔHvap = 40.7 kJ/ mol; ΔHfus = 6.01 kJ/mol.
Consider a 75.0-g sample of H2O(g) at 125oC. What phase or phases are present when 215 kJ of energy is removed from this sample? (See Exercise 91.)
A 0.250-g chunk of sodium metal is cautiously dropped into a mixture of 50.0 g of water and 50.0 g of ice, both at 0oC. The reaction is 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g) ΔH = –368 kJ Will the ice melt? Assuming the final mixture has a specific heat capacity of 4.18 Jg-1oC-1, calculate the
A 20.0-g sample of ice at 210.0oC is mixed with 100.0 g of water at 80.0oC. Calculate the final temperature of the mixture assuming no heat loss to the surroundings. The heat capacities of H2O(s) and H2O(l) are 2.08 Jg-1oC-1 and 4.18 Jg-1oC-1, respectively, and the enthalpy of fusion for ice is
An ice cube tray contains enough water at 22.0oC to make 18 ice cubes, each of which has a mass of 30.0 g. The tray is placed in a freezer that uses CF2Cl2 as a refrigerant. The heat of vaporization of CF2Cl2 is 158 J/g. What mass of CF2Cl2 must be vaporized in the refrigeration cycle to convert
In regions with dry climates, evaporative coolers are used to cool air. A typical electric air conditioner is rated at 1.00 × 104 Btu/ h (1 Btu, or British thermal unit, equals the amount of energy needed to raise the temperature of 1 lb of water by 18F). How much water must be evaporated each
In each of the following groups of substances, pick the one that has the given property. Justify each answer. a. highest boiling point: CCl4, CF4, CBr4 b. lowest freezing point: LiF, F2, HCl c. lowest vapor pressure at 25oC: CH3OCH3, CH3CH2OH, CH3CH2CH3 d. greatest viscosity: H2S, HF, or H2O2 e.
Compare and contrast the phase diagrams of water and carbon dioxide. Why doesn’t CO2 have a normal melting point and a normal boiling point, whereas water does? The slopes of the solid/liquid lines in the phase diagrams of H2O and CO2 are different. What do the slopes of the solid/liquid lines
Define critical temperature and critical pressure. In terms of the kinetic molecular theory, why is it impossible for a substance to exist as a liquid above its critical temperature?
The critical point of NH3 is 132oC and 111 atm, and the critical point of N2 is –147oC and 34 atm. Which of these substances cannot be liquefied at room temperature no matter how much pressure is applied? Explain.
Like most substances, bromine exists in one of the three typical phases. Br2 has a normal melting point of 27.2oC and a normal boiling point of 59oC. The triple point for Br2 is 27.3oC and 40 torr, and the critical point is 320oC and 100 atm. Using this information, sketch a phase diagram for
Consider the following phase diagram. What phases are present at points A through H? Identify the triple point, normal boiling point, normal freezing point, and critical point. Which phase is denser, solid or liquid?
Use the accompanying phase diagram for sulfur to answer the following questions. (The phase diagram is not to scale.)a. How many triple points are in the phase diagram? b. What phases are in equilibrium at each of the triple points? c. What phase is stable at room temperature and 1.0 atm
Use the accompanying phase diagram for carbon to answer the following questions.a. How many triple points are in the phase diagram?b. What phases can coexist at each triple point?c. What happens if graphite is subjected to very high pressures at room temperature?d. If we assume that the density
Iodine, like most substances, exhibits only three phases: solid, liquid, and vapor. The triple point of iodine is at 90 torr and 115oC. Which of the following statements concerning liquid I2 must be true? Explain your answer. a. I2(l) is more dense than I2(g). b. I2(l) cannot exist above 115oC. c.
The melting point of a fictional substance X is 225oC at 10.0 atm. If the density of the solid phase of X is 2.67 g/cm3 and the density of the liquid phase is 2.78 g/cm3 at 10.0 atm, predict whether the normal melting point of X will be less than, equal to, or greater than 225oC. Explain.
Consider the following data for xenon: Triple point: ...... –121oC, 280 torr Normal melting point: ... –112oC Normal boiling point: ... –107oC Which is more dense, Xe(s) or Xe(l)? How do the melting point and boiling point of xenon depend on pressure?
Rationalize the difference in boiling points for each of the following pairs of substances:a. n-pentane CH3CH2CH2CH2CH3 36.2oCb. HF 20oC HCl 85oC c. HCl 85oC LiCl 1360oC d. n-pentane CH3CH2CH2CH2CH3 36.2oC n-hexane CH3CH2CH2CH2CH2CH3 69oC
Some water is placed in a sealed glass container connected to a vacuum pump (a device used to pump gases from a container), and the pump is turned on. The water appears to boil and then freezes. Explain these changes by using the phase diagram for water. What would happen to the ice if the vacuum
Oil of wintergreen, or methyl salicylate, has the following structure:Methyl 4-hydroxybenzoate is another molecule with exactly the same molecular formula; it has the following structure: Account for the large difference in the melting points of the two substances.
You have three covalent compounds with three very different boiling points. All of the compounds have similar molar mass and relative shape. Explain how these three compounds could have very different boiling points.
Boron nitride (BN) exists in two forms. The first is a slippery solid formed from the reaction of BCl3 with NH3, followed by heating in an ammonia atmosphere at 750oC. Subjecting the first form of BN to a pressure of 85,000 atm at 1800oC produces a second form that is the second hardest substance
Consider the following data concerning four different substances.Label the four substances as either ionic, network, metallic, or molecular solids.
A special vessel (see Fig. 16.52) contains ice and super-cooled water (both at 10oC) connected by vapor space. Describe what happens to the amounts of ice and water as time passes.Figure 16.52.
Consider a cation in a trigonal hole. What size ion will just fit in the hole if the packed spheres have radius R?
Use the diagram of the unit cell for the hexagonal closest packed structure in Fig. 16.14 to determine the net number of atoms in the hcp unit cell.Figure 16.14.
Argon has a cubic closest packed structure as a solid. Assuming that argon has a radius of 190 pm, calculate the density of solid argon.
Rubidium chloride has the sodium chloride structure at normal pressures but assumes the cesium chloride structure at high pressures. What ratio of densities is expected for these two forms? Does this change in structure make sense on the basis of simple models?
In some regions of the southwest United States, the water is very hard. For example, in Las Cruces, New Mexico, the tap water contains about 560 mg of dissolved solids per milliliter. Reverse osmosis units are marketed in this area to soften water. A typical unit exerts a pressure of 8.0 atm and
For each of the following solutesolvent combinations, state the sign and relative magnitudes for ÎH1, ÎH2, ÎH3, and ÎHsoln (as defined in Fig. 17.1 of the text). Explain your answers.Figure 17.1
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?
a. Use the following data to calculate the enthalpy of hydration for calcium chloride and calcium iodide.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. Na+ or Mg2+ b. Mg2+ or Be2+ c. Fe2+ or Fe3+ d. F- or Br- e. Cl- or ClO4- f. ClO4- or SO4 2-
Write equations showing the ions present after the following strong electrolytes are dissolved in water. a. HNO3 b. Na2SO4 c. Al(NO3)3 d. SrBr2 e. KClO4 f. NH4Br g. NH4NO3 h. CuSO4 i. NaOH
For each of the following pairs, predict which substance would be more soluble in water.
Which solvent, water or carbon tetrachloride, would you choose to dissolve each of the following? a. KrF2 b. SF2 c. SO2 d. CO2 e. MgF2 f. CH2O g. CH2PCH2
Rationalize the trend in water solubility for the following simple alcohols.
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
The solubility of nitrogen in water is 8.21 × 10-4 mol/ L at 0oC when the N2 pressure above water is 0.790 atm. Calculate the Henry’s law constant for N2 in units of L atm/mol for Henry’s law in the form P = kC, where C is the gas concentration in mol/ L. Calculate the solubility of N2 in
In Exercise 112 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 Henry’s law. Use the data given in that problem to calculate the partial
Rationalize the temperature dependence of the solubility of a gas in terms of the kinetic molecular theory.
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. Discuss.
Which of the following will have the lowest total vapor pressure at 25oC? Which has the highest vapor pressure at 25oC? At 25oC, the vapor pressure of pure water is 23.8 torr. a. Pure water
Match the vapor pressure diagrams with the solutesolvent combinations and explain your answers.
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.Table 17.5
The freezing point of t-butanol is 25.50oC and Kf is 9.1oC 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 24.59oC, how many grams of water are present in the sample?
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 25oC? Assume that the density of the fluid is 1.0 g/cm3. (The density of mercury is 13.6 g/cm3.)
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?
Consider the following: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 20oC to purify the water by reverse osmosis. Assume that NaCl is completely dissociated.
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.
In the winter of 1994, record low temperatures were registered throughout the United States. For example, in Champaign, Illinois, a record low of 229oF was registered. At this temperature can salting icy roads with CaCl2 be effective in melting the ice? a. Assume that i = 3.00 for CaCl2. b. Assume
What stabilizes a colloidal suspension? Explain why adding heat or adding an electrolyte can cause the suspended particles to settle out.
The solubility of benzoic acid,
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
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 22.3oC when 1.32 g of anthraquinone is dissolved in 11.4 g of camphor. Determine the empirical and molecular
A forensic chemist is given a white solid that is suspected of being pure cocaine (C17H21NO4, molar mass = 303.36 g/mol). She dissolves 1.22 + 0.01 g of the solid in 15.60 + 0.01 g of benzene. The freezing point is lowered by 1.32 + 0.04oC. a. What is the molar mass of the substance? Assuming that
You add an excess of solid MX in 250 g of water. You measure the freezing point and find it to be 20.028oC. What is the Ksp of the solid?
A solid consists of a mixture of NaNO3 and Mg(NO3)2. When 6.50 g of this solid is dissolved in 50.0 g of water, the freezing point is lowered by 5.40oC. What is the composition of the solid (by mass)? Assume ideal behavior.
Consider an initial mixture of N2 and H2 gases that can be represented as follows.The gases react to form ammonia gas (NH3) as represented by the following concentration profile. a. Label each plot on the graph as N2, H2, or NH3 and explain your answers. b. Explain the relative shapes of the
Consider the following reactions at some temperature: 2NOCl( g) ⇌ 2NO( g) + Cl2( g) K = 1.6 × 1025 2NO( g) ⇌ N2( g) + O2( g) K = 1 × 1031 For each reaction some quantities of the reactants were placed in separate containers and allowed to come to equilibrium. Describe the relative amounts
Consider the following reaction: H2O( g) + CO(g) ⇌ H2( g) + CO2(g) Amounts of H2O, CO, H2, and CO2 are put into a flask so that the composition corresponds to an equilibrium position. If the CO placed in the flask is labeled with radioactive 14C, will 14C be found only in CO molecules for an
Consider the following reaction at some temperature:H2O(g) + CO(g) H2(g) + CO2(g) K = 2.0Some molecules of H2O and CO are placed in a 1.0- L container as shown below.When equilibrium is reached, how many molecules of H2O, CO, H2, and CO2 are present? Do this problem by trial and
Consider the following generic reaction: 2A2B(g) 2A2(g) + B2(g) Some molecules of A2B are placed in a 1.0- L container. As time passes, several snapshots of the reaction mixture are taken as illustrated below.Which illustration is the first to represent an equilibrium mixture? Explain.
There is only one value of the equilibrium constant for a particular system at a particular temperature, but there are an infinite number of equilibrium positions. Explain.
Explain the difference between K, Kp, and Q.
What are homogeneous equilibria? Heterogeneous equilibria? What is the difference in writing K expressions for homogeneous versus heterogeneous reactions? Summarize which species are included in K expressions and which species are not included.
Write expressions for K and Kp for the following reactions. a. 2NH3(g) + CO2(g) ⇌ N2CH4O(s) + H2O(g) b. 2NBr3(s) ⇌ N2(g) + 3Br2(g) c. 2KClO3(s) ⇌ 2KCl(s) + 3O2(g) d. CuO(s) + H2(g) ⇌ Cu(l) + H2O(g)
For which reactions in Exercise 19 is Kp equal to K? Exercise 19: a. 2NH3(g) + CO2(g) ⇌ N2CH4O(s) + H2O(g) b. 2NBr3(s) ⇌ N2(g) + 3Br2(g) c. 2KClO3(s) ⇌ 2KCl(s) + 3O2(g) d. CuO(s) + H2(g) ⇌ Cu(l) + H2O(g)
At a particular temperature, a 3.0- L flask contains 2.4 moles of Cl2, 1.0 mole of NOCl, and 4.5 × 10-3 mole of NO. Calculate K at this temperature for the following reaction. 2NOCl(g) ⇌ 2NO(g) + Cl2(g)
At 1100 K, Kp 5 0.25 for the reaction 2SO2(g) + O2(g) ⇌ 2SO3(g) What is the value of K at this temperature?
At 327oC, the equilibrium concentrations are [CH3OH] = 0.15 M, [CO] = 0.24 M, and [H2] = 1.1 M for the reaction CH3OH(g) ⇌ CO(g) + 2H2(g). Calculate Kp at this temperature.
For the reaction H2(g) + Br2(g) ⇌ 2HBr(g) Kp = 3.5 × 104 at 1495 K. What is the value of Kp for the following reactions at 1495 K? a. HBr(g) ⇌ 1/2 H2(g) + 1/2 Br2(g) b. 2HBr(g) ⇌ H2(g) + Br2(g) c. 1/2H2(g) + 1/2 Br2(g) ⇌ HBr(g)
At a particular temperature, a 2.00- L flask at equilibrium contains 2.80 × 10-4 mole of N2, 2.50 × 10-5 mole of O2, and 2.00 × 10-2 mole of N2O. Calculate K at this temperature for the reaction 2N2(g) + O2(g) ⇌ 2N2O(g) If [N2] = 2.00 × 10-4 M, [N2O] = 0.200 M, and [O2] = 0.00245 M, does
The following equilibrium pressures were observed at a certain temperature for the reaction N2(g) + 3H2(g) ⇌ 2NH3(g) PNH3 = 3.1 × 10-2 atm PN2 = 8.5 × 10-1 atm PH2 = 3.1 × 10-3 atm Calculate the value for the equilibrium constant Kp at this temperature. If PN2 = 0.525 atm, PNH3 = 0.0167 atm,
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