Describe in detail the microscopic processes that take place when a liquid boils. What kind of forces must be overcome? Are any chemical bonds broken during these processes?
> When is a scientific theory considered to be successful? Are all theories successful? Will a theory that has been successful in the past necessarily be successful in the future?
> What is a scientific law? What is a theory? How do these concepts differ? Does a law explain a theory, or does a theory attempt to explain a law?
> A 500.-mL sample of O2 gas at 24 °C was prepared by decomposing a 3% aqueous solution of hydrogen peroxide, H2O2, in the presence of a small amount of manganese catalyst by the reaction 2H2O2 (aq) 2H2O(g) + O2(g) The oxygen thus pr
> A sample of oxygen gas is saturated with water vapor at 27 °C. The total pressure of the mixture is 772 torr, and the vapor pressure of water is 26.7 torr at 27 °C. What is the partial pressure of the oxygen gas?
> Make the indicated pressure conversions. a. 45.2 kPa to atmospheres b. 755 mm Hg to atmospheres c. 802 torr to kilopascals d. 1.04 atm to millimeters of mercury
> The “Chemistry in Focus” segment Snacks Need Chemistry, Too! discusses why popcorn “pops.” You can estimate the pressure inside a kernel of popcorn at the time of popping by using the ideal gas law. Basically, you determine the mass of water released whe
> What will the volume of the sample become if 459 mL of an ideal gas at 27 °C and 1.05 atm is cooled to 15 °C and 0.997 atm?
> Suppose that 1.29 g of argon gas is confined to a volume of 2.41 L at 29 °C. What would be the pressure in the container? What would the pressure become if the temperature were raised to 42 °C without a change in volume?
> Suppose that a 1.25-g sample of neon gas is confined in a 10.1-L container at 25 °C. What will be the pressure in the container? Suppose the temperature is then raised to 50 °C. What will the new pressure be after the temperature is increased?
> At what temperature (in °C) will a 5.00-g sample of neon gas exert a pressure of 1.10 atm in a 7.00-L container?
> Which of the following molecules contain polar covalent bonds? a. phosphorus, P4 b. oxygen, O2 c. ozone, O3 d. hydrogen fluoride, HF
> What volume will 2.04 g of helium gas occupy at 100. °C and 785 mm Hg pressure?
> Determine the pressure in a 125-L tank containing 56.2 kg of oxygen gas at 21 °C.
> Which of the following statements is(are) true? a. If the number of moles of a gas is doubled, the volume will double, assuming the pressure and temperature of the gas remain constant. b. If the temperature of a gas increases from 25 °C to 50 °C, the vol
> Consider the unbalanced chemical equation: CaSiO3(s) + HF(g) / CaF2(aq) + SiF4(g) + H2O(l) Suppose a 32.9-g sample of CaSiO3 is reacted with 31.8 L of HF at 27.0 °C and 1.00 atm. Assuming the reaction goes to completion, calculate the mass of SiF4 and H
> A 20.0-L nickel container was charged with 0.859 atm of xenon gas and 1.37 atm of fluorine gas at 400 °C. The xenon and fluorine react to form xenon tetrafluoride. What mass of xenon tetrafluoride can be produced, assuming 100% yield?
> A large flask with a volume of 936 mL is evacuated and found to have a mass of 134.66 g. It is then filled to a pressure of 0.967 atm at 31 °C with a gas of unknown molar mass and then reweighed to give a new mass of 135.87 g. What is the molar mass of t
> A certain flexible weather balloon contains helium gas at a volume of 855 L. Initially, the balloon is at sea level where the temperature is 25 °C and the barometric pressure is 730 torr. The balloon then rises to an altitude of 6000 ft, where the pressu
> A steel cylinder contains 150.0 moles of argon gas at a temperature of 25 °C and a pressure of 8.93 MPa. After some argon has been used, the pressure is 2.00 MPa at a temperature of 19 °C. What mass of argon remains in the cylinder?
> A glass vessel contains 28 g of nitrogen gas. Assuming ideal behavior, which of the processes listed below would double the pressure exerted on the walls of the vessel? a. Adding 28 g of oxygen gas b. Raising the temperature of the container from 273 °
> Complete the following table for an ideal gas. P(atm) V(L) n (mol) 6.74 2.00 155 °C 0.300 1.74 155 K 4.47 25.0 2.19 °C 2.25 10.5 93 °C
> Which of the following molecules contain polar covalent bonds? a. water, H2O b. carbon monoxide, CO c. fluorine, F2 d. nitrogen, N2
> The “Chemistry in Focus” segment Breath Fingerprinting discusses using breath analysis to diagnose diseases. The volume of the average human breath is approximately 500 mL, and carbon dioxide (CO2) makes up 4% of what we exhale. Determine the mass of car
> The “Chemistry in Focus” segment The Chemistry of Air Bags discusses how the decomposition of sodium azide inflates the air bag. Use the balanced chemical equation in the segment to determine the mass of sodium azide required to inflate an air bag to 70.
> Concentrated hydrogen peroxide solutions are explosively decomposed by traces of transition metal ions (such as Mn or Fe): 2H2O2(aq) 2H2O(l) + O2(g) What volume of pure O2(g), collected at 27 °C and 764 torr, would be generated
> What volume of CO2 measured at STP is produced when 27.5 g of CaCO3 is decomposed? CaCO3(s) / CaO(s) + CO2(g)
> Consider the flasks in the following diagrams. a. Which is greater, the initial pressure of helium or the initial pressure of neon? How much greater? b. Assuming the connecting tube has negligible volume, draw what each diagram will look like after th
> A sample of oxygen gas has a volume of 125 L at 25 °C and a pressure of 0.987 atm. Calculate the volume of this oxygen sample at STP.
> What volume does 35 moles of N2 occupy at STP?
> When sodium bicarbonate, NaHCO3(s), is heated, sodium carbonate is produced, with the evolution of water vapor and carbon dioxide gas. 2NaHCO3(s) / Na2CO3(s) + H2O(g) + CO2(g) What total volume of gas, measured at 29 °C and 769 torr, is produced when 1.
> Consider the following unbalanced chemical equation: Cu2S(s) + O2(g) Cu2O(s) + SO2(g) What volume of oxygen gas, measured at 27.5 °C and 0.998 atm, is required to react with 25 g of copper(I) sulfide? What volume of sulfur diox
> The following demonstration takes place in a two-step process: First, solid calcium carbide (CaC2) reacts with liquid water to produce acetylene gas (C2H2) and aqueous calcium hydroxide. Second, the acetylene gas produced is then ignited with a match, ca
> Discuss the similarities and differences between the arrangements of molecules and the forces between molecules in liquid water versus steam, and in liquid water versus ice.
> Consider the following chemical equation: N2(g) + 3H2(g) 2NH3(g) What volumes of nitrogen gas and hydrogen gas, each measured at 11 °C and 0.998 atm, are needed to produce 5.00 g of ammonia?
> You have two rigid gas cylinders. Gas cylinder A has a volume of 48.2 L and contains N2(g) at 8.35 atm at 25 °C. Gas cylinder B has a volume of 22.0 L and contains He(g) at 25 °C. When the two cylinders are connected with a valve of negligible volume and
> A mixture at 33 °C contains H2 at 325 torr, N2 at 475 torr, and O2 at 650. torr. a. What is the total pressure of the gases in the system? b. Which gas contains the greatest number of moles?
> An aluminum can contain a small amount of water and is boiled with the lid removed. The heat is then turned off, and the can is sealed. Over time, the can crumples. a. Why doesn’t the can explode or crumple when the water is heated
> If 3.20 g of nitrogen gas occupies a volume of 1.71 L at 0 °C and a pressure of 1.50 atm, what would the volume become if 8.80 g of nitrogen gas were added at constant conditions of temperature and pressure?
> A 22-g sample of neon gas exerts a pressure of 2.0 atm at a certain temperature and volume. What pressure does a 44-g sample of argon gas exert at these conditions of temperature and volume?
> Which of the following statements is(are) true? a. LiF will have a higher vapor pressure at 25 °C than H2S. b. HF will have a lower vapor pressure at 250 °C than HBr. c. Cl2 will have a higher boiling point than Ar. d. HCl is more soluble in water th
> Which of the following statements about intermolecular forces is(are) true? a. London dispersion forces are the only type of intermolecular force that nonpolar molecules exhibit. b. Molecules that have only London dispersion forces will always be gases
> Describe, on a microscopic basis, the processes of evaporation and condensation. Which process requires an input of energy? Why?
> Given each of the following sets of values for three of the gas variables, calculate the unknown quantity. a. P = 1.034 atm; V = 21.2 mL; n = 0.00432 mol; T =? K b. P =? atm; V = 1.73 mL; n = 0.000115 mol; T = 182 K c. P = 1.23 mm Hg; V =? L; n = 0.77
> Make the indicated pressure conversions. a. 1.54 * 105 Pa to atmospheres b. 1.21 atm to pascals c. 97,345 Pa to mm Hg d. 1.32 kPa to pascals
> Given each of the following sets of values for three of the gas variables, calculate the unknown quantity. a. P = 21.2 atm; V = 142 mL; n = 0.432 mol; T =? K b. P =? atm; V = 1.23 mL; n = 0.000115 mol; T = 293 K c. P = 755 mm Hg; V =? mL; n = 0.473 mo
> You have a gas in a container fitted with a piston, and you change one of the conditions of the gas such that a change takes place, as shown below: State three distinct changes you can make to accomplish this, and explain why each would work. volum
> Although the noble gas elements are monatomic and could not give rise to dipole–dipole forces or hydrogen bonding, these elements still can be liquefied and solidified. Explain.
> For each of the following sets of volume/temperature data, calculate the missing quantity. Assume that the pressure and the amount of gas remain constant. a. V = 22.4 L at 0 °C; V = 44.4 L at? K b. V = 1.0 3 1023 mL at 2272 °C; V =? at 25 °C c. V = 32
> Arrange the atoms and/or ions in the following groups in order of decreasing size. a. O, O+, O2- b. Fe2+, Ni2+, Zn2+ c. Ca2+, K+, Cl-
> What are London dispersion forces and how do they arise in a nonpolar molecule? Are London forces typically stronger or weaker than dipole–dipole attractions between polar molecules? Are London forces stronger or weaker than covalent bonds? Explain.
> A particular balloon is designed by its manufacturer to be inflated to a volume of no more than 2.5 L. If the balloon is filled with 2.0 L of helium at sea level, is released, and rises to an altitude at which the atmospheric pressure is only 500. mm Hg,
> Consider the following series of atoms or ions: S2-, S, S2+, Cs+, Sr2+. a. Which of the species has the smallest size? b. Which of the species has the largest ionization energy?
> What do we call the energies required, respectively, to melt and to vaporize 1 mole of a substance? Which of these energies is always larger for a given substance? Why?
> Convert the following pressures into pascals. a. 774 torr b. 0.965 atm c. 112.5 kPa d. 801 mm Hg
> For each of the following sets of pressure/volume data, calculate the missing quantity. Assume that the temperature and the amount of gas remain constant. a. V = 123 L at 4.56 atm; V =? at 1002 mm Hg b. V = 634 mL at 25.2 mm Hg; V = 166 mL at? atm c.
> A 2.50-L container at 1.00 atm and 248°C is filled with 5.41 g of a monatomic gas. a. Determine the identity of the gas. b. Assuming the 2.50-L container is a large elastic balloon, predict what will happen when 10.0 g of oxygen gas is added to the bal
> Cake mixes and other packaged foods that require cooking often contain special directions for use at high elevations. Typically these directions indicate that the food should be cooked longer above 5000 ft. Explain why it takes longer to cook something a
> Describe, on both a microscopic and a macroscopic basis, what happens to a sample of water as it is cooled from room temperature to 50 °C below its normal freezing point.
> What are some important uses of water, both in nature and in industry? What is the liquid range for water?
> As weather balloons rise from the earth’s surface, the pressure of the atmosphere becomes less, tending to cause the volume of the balloons to expand. However, the temperature is much lower in the upper atmosphere than at sea level. Would this temperatur
> Why is the molecular structure of H2O nonlinear, whereas that of BeF2 is linear, even though both molecules consist of three atoms?
> Carbon dioxide gas, saturated with water vapor, can be produced by the addition of aqueous acid to calcium carbonate. CaCO3(s) + 2H+(aq) / Ca2+(aq) + H2O(l) + CO2(g) How many moles of CO2(g), collected at 60. °C and 774 torr total pressure, are produced
> A helium tank contains 25.2 L of helium at 8.40 atm pressure. Determine how many 1.50-L balloons at 755 mm Hg can be inflated with the gas in the tank, assuming that the tank will also have to contain He at 755 mm Hg after the balloons are filled (that i
> When ammonium carbonate is heated, three gases are produced by its decomposition. (NH4)2CO3(s) 2NH3(g) + CO2(g) + H2O(g) What total volume of gas is produced, measured at 453 °C and 1.04 atm, if 52.0 g of ammonium carbonate is
> In each of the following groups, which element is the most electronegative? Which is the least electro negative? a. K, Na, H b. F, Br, Na c. B, N, F
> Write a Lewis structure for each of the following simple molecules. Show all bonding valence electron pairs as lines and all nonbonding valence electron pairs as dots. a. GeH4 b. ICl c. NI3 d. PF3
> What is the total number of valence electrons in each of the following molecules? a. HNO3 b. H2SO4 c. H3PO4 d. HClO4
> When a person has a severe fever, one therapy to reduce the fever is an “alcohol rub.” Explain how the evaporation of alcohol from the person’s skin removes heat energy from the body.
> Consider the flasks in the following diagrams. Assuming the connecting tube has negligible volume, draw what each diagram will look like after the stopcock between the two flasks is opened. Also, solve for the final pressure in each case, in terms of t
> Which of the following statements is(are) true? a. At constant temperature, the lighter the gas molecules, the faster the average velocity of the gas molecules. b. At constant temperature, the heavier the gas molecules, the larger the average kinetic e
> On the basis of their electron configurations, predict the formula of the simple binary ionic compound likely to form when the following pairs of elements react with each other. a. sodium, Na, and selenium, Se b. rubidium, Rb, and fluorine, F c. potas
> What is an alloy? Explain the differences in structure between substitutional and interstitial alloys. Give an example of each type.
> What is a network solid? Give an example of a network solid and describe the bonding in such a solid. How does a network solid differ from a molecular solid?
> During the making of steel, iron(II) oxide is reduced to metallic iron by treatment with carbon monoxide gas. FeO(s) + CO(g) / Fe(s) + CO2(g) Suppose 1.45 kg of Fe reacts. What volume of CO(g) is required, and what volume of CO2(g) is produced, each mea
> Explain the overall trend in the following melting points in terms of the forces among particles in the solids indicated. Hydrogen, H2………………….-259 °C Ethyl alcohol, C2H5OH………-114 °C Water, H2O……………………….…0 °C Sucrose, C12H22O11…………...186 °C Calcium chlo
> Describe in detail the microscopic processes that take place when a solid melts and when a liquid boils. What kind of forces must be overcome? Are any chemical bonds broken during these processes?
> In general terms, what is a chemical bond?
> On the basis of the electronegativity values given in Fig. 12.3, indicate which is the more polar bond in each of the following pairs. a. N-P or N-O b. N-C or N-O c. N-S or N-C d. N-F or N-S
> Dinitrogen monoxide, N2O, reacts with propane, C3H8, to form nitrogen, N2; carbon dioxide, CO2; and water, H2O. a. Write a balanced chemical equation for this reaction, treating all substances as gases. Include phases in your equation. b. Two reservoir
> A mixture contains 5.00 g each of O2, N2, CO2, and Ne gas. Calculate the volume of this mixture at STP. Calculate the partial pressure of each gas in the mixture at STP.
> The forces holding together a molecular solid are much (stronger/ weaker) than the forces between particles in an ionic solid.
> A common prank on college campuses is to switch the salt and sugar on dining hall tables, which is usually easy because the substances look so much alike. Yet, despite the similarity in their appearance, these two substances differ greatly in their prope
> Consider the following unbalanced chemical equation in which element X is unknown: X(s) + F2(g) ( XF3(s) If 9.15 g of element X(s) is completely reacted with 4.00 L of fluorine gas at 250 °C and 2.50 atm, what is the identity of X?
> Two molecules that contain the same number of each kind of atom but that have different molecular structures are said to be isomers of each other. For example, both ethyl alcohol and dimethyl ether (shown below) have the formula C2H6O and are isomers. Ba
> If water is added to magnesium nitride, ammonia gas is produced when the mixture is heated. Mg3N2(s) + 3H2O(l) 3MgO(s) + 2NH3(g) If 10.3 g of magnesium nitride is treated with water, what volume of ammonia gas would be co
> Although we generally think of combustion reactions as involving oxygen gas, other rapid oxidation reactions are also referred to as combustions. For example, if magnesium metal is placed into chlorine gas, a rapid oxidation takes place, and magnesium ch
> Calcium carbide, CaC2, reacts with water to produce acetylene gas, C2H2. CaC2(s) + 2H2O(l) C2H2(g) + Ca(OH)2(s) What volume of acetylene at 25 °C and 1.01 atm is generated by the complete reaction of 2.49 g of calcium carbide? What
> Explain the difference between intramolecular and intermolecular forces.
> Ammonia and gaseous hydrogen chloride combine to form ammonium chloride. NH3(g) + HCl(g) NH4Cl(s) If 4.21 L of NH3(g) at 27 °C and 1.02 atm is combined with 5.35 L of HCl(g) at 26 °C and 0.998 atm, what mass of NH4Cl(s) will be produced
> For each of the following molecules, predict both the molecular structure and bond angles around the central atom. a. SeS2 b. SeS3 c. SO2 d. CS2
> Consider the following reaction for the combustion of octane, C8H18: 2C8H18(l) + 25O2(g) / 16CO2(g) + 18H20(l) What volume of oxygen gas at STP would be needed for the complete combustion of 10.0 g of octane?
> Which substance in each pair would be expected to be more volatile at a particular temperature? Explain your reasoning. a. H2O(l) or H2S(l) b. H2O(l) or CH3OH(l) c. CH3OH(l) or CH3CH2OH(l)
> Calcium oxide can be used to “scrub” carbon dioxide from air. CaO(s) + CO2(g) CaCO3(s) What mass of CO2 could be absorbed by 1.25 g of CaO? What volume would this CO2 occupy at STP?
> Using the VSEPR theory, predict the molecular structure of each of the following polyatomic ions. a. dihydrogen phosphate ion, H2PO4- b. perchlorate ion, ClO4- c. sulfite ion, SO32-
> Which substance in each pair would be expected to have a lower boiling point? Explain your reasoning. a. CH3OH or CH3CH2CH2OH b. CH3CH3 or CH3CH2OH c. H2O or CH4
> Explain, in terms of the kinetic molecular theory, how an increase in the temperature of a gas confined to a rigid container causes an increase in the pressure of the gas.
> How is the phenomenon of temperature explained on the basis of the kinetic molecular theory? What microscopic property of gas molecules is reflected in the temperature measured?
> Consider the following molecules: CH3OH, CH4, H2O, C2H6. a. Draw the Lewis structure for each molecule, and indicate whether each is polar or nonpolar. b. At room temperature, two of these compounds exist as a liquid, and two of these compounds exist a
> What does it mean to say that a bond is polar? Give two examples of molecules with polar bonds. Indicate in your examples the direction of the polarity.
> For the indicated atom in each of the following molecules or ions, give the number and arrangement of the electron pairs around that atom. a. As in AsO43- b. Se in SeO42- c. S in H2S
