Unit 3 Chem Assignments + test
(c) CH3OH = 92; because a high vapor pressure indicates weak interactions between molecules
(Equilibrium vapor pressure at 20º) (a) C6H6 = 75 torr (b) C2H5OH = 44 (c) CH3OH = 92 (d) C2H6O2 = 0.06 Based on the data in the table above, which of the following liquid substances has the weakest intermolecular forces?
C III only
A sample of an ideal gas is cooled from 50.0oC to 25.0oC in a sealed container of constant volume. Which of the following values for the gas will decrease? I. The average molecular mass of the gas II. The average distance between the molecules III. The average speed of the molecules A I only B II only C III only D I and III E II and III
D 2.00 atm
A sealed vessel contains 0.200 mol of oxygen gas, 0.100 mol of nitrogen gas, and 0.200 mol of argon gas. The total pressure of the gas mixture is 5.00 atm. The partial pressure of the argon is... A 0.200 atm B 0.500 atm C 1.00 atm D 2.00 atm E 5.00 atm
(d) There are dipole-induced dipole and London dispersion interactions between water and benzene.
Benzene, C6H6 , has the structure shown above. Considering the observation that benzene is only sparingly soluble in water, which of the following best describes the intermolecular forces of attraction between water and benzene? (a) Benzene is nonpolar, therefore there are no forces between water and benzene. (b) The H atoms in benzene form hydrogen bonds with the O atoms in water. (c) Benzene is hydrophobic, therefore there is a net repulsion between water and benzene. (d) There are dipole-induced dipole and London dispersion interactions between water and benzene.
D 5.6×1014s−1
Electromagnetic radiation with a maximum wavelength of 540nm (5.4×10−7 m ) is needed for the study of the photoelectric effect in potassium atoms. What is the approximate frequency that corresponds to this wavelength? A 1.8×10−15s−11.8×10−15s−1 B 1.6×102s−11.6×102s−1 C 1.9×106s−11.9×106s−1 D 5.6×1014s−1
(d) CaCl2 with twice the molarity as the solution in vessel 1.
Equal volumes of solutions in two different vessels are represented above. If the solution represented in vessel 1 is KCL (4:4), then the solution in vessel 2 could be the aqueous solution of... (a) KCL with the same molarity as the solution in vessel 1. (b) KCL with twice the molarity as the solution in vessel 1. (c) CaCl2 with the same molarity as the solution in vessel 1. (d) CaCl2 with twice the molarity as the solution in vessel 1.
A 0.025 M
If 50. mL of 1.0 M NaOH is diluted with distilled water to a volume of 2.0 L, the concentration of the resulting solution is A 0.025 M B 0.050 M C 0.10 M D 0.50 M E 1.0 M
D Y is more polar than X.
In a paper chromatography experiment, a sample of a pigment is separated into two components, X and Y, as shown in the figure above. The surface of the paper is moderately polar. What can be concluded about X and Y based on the experimental results? A X has a larger molar mass than Y does. B Y has a larger molar mass than X does. C X is more polar than Y. D Y is more polar than X.
A 5×10−19J5×10−19J
In an experiment on the photoelectric effect, a photon with a frequency of 7×1014s−1 was absorbed by a sample. What is the approximate energy of this photon? A 5×10−19J5×10−19J B 1×10−15J1×10−15J C 2×106J2×106J D 1×1048J1×1048J
(c) C6H14, hexane; because there is no oxygen that can form strong hydrogen bonds with water compared to the other compounds.
Of the following organic compounds, which is LEAST soluble in water at 298ºK? (a) CH3OH, methanol (b) CH3CH2CH2OH, I-propanol (c) C6H14, hexane (d) C6H12O6, glucose (e) CH2COOH, ethanoic (acetic) acid
B are relatively far apart
Of the following, the best explanation for the fact that most gases are easily compressed is that the molecules in a gas... are in constant motion B are relatively far apart C have relatively small masses D have a real, nonzero volume E move slower as temperature decreases
H2
The London (dispersion) forces are weakest for which of the following gases under the same conditions of temperature and pressure? (a) H2 (b) O2 (c) Xe (d) F2 (e) N2
A The peak of the curve would be higher because more light would be absorbed.
The absorption spectrum of a certain red dye is shown above. If a student analyzing the same concentration of this dye neglected to wipe fingerprints off the cuvette before placing it in the spectrophotometer, how would the absorption curve be affected? A The peak of the curve would be higher because more light would be absorbed. B The peak of curve would be lower because less light would be absorbed. C The peak of the curve would be shifted to the left because less light would be absorbed. D The peak of the curve would be shifted to the right because more light would be absorbed.
B Mg2+ , because it has the largest charge-to-size ratio.
The diagram above represents four cations, all shown to the same scale. Which cation would be predicted by Coulomb's law to have the strongest ion-dipole attraction to water, and why? A Li+Li+ , because it is the smallest group 1 metal ion. B Mg2+Mg2+ , because it has the largest charge-to-size ratio. C Na+Na+ , because it has the smallest charge-to-size ratio. D Ca2+Ca2+ , because it is the largest group 2 metal ion.
C Solvent CC
The diagram above shows thin-layer chromatograms of the same mixture of two compounds. Based on the chromatograms, which solvent would be most effective at separating the two compounds if the same stationary phase is used for column chromatography? A Solvent AA B Solvent BB C Solvent CC D Solvent DD
D SO2SO2, because it has the largest molecular volume.
The graph above shows how a particular real gas deviates from ideal behavior at very high pressures. Based on this information, which of the following is most likely the gas and gives the reason based on kinetic molecular theory? A H2H2, because it has the smallest mass. B N2N2, because its molecules have a triple bond. C NeNe, because it has a completely filled valence shell. D SO2SO2, because it has the largest molecular volume.
C have stronger intermolecular attractions than the other three gases
The table below contains information about samples of four different gases at 273 K. The samples are in four identical rigid containers numbered 1 through 4.The best explanation for the lower pressure in container 4 is that SO2 molecules... A have a larger average speed than the other three gases B occupy a larger portion of the container volume than the other three gases C have stronger intermolecular attractions than the other three gases D contain pi bonds, while the other gases contain only the other bond
D 110. ML
The volume of distilled water that should be added to 10.0 mL of 6.00 M HCl(aq) in order to prepare a 0.500 M HCl(aq) solution is approximately A 50.0 mL B 60.0 mL C 100. ML D 110. ML E 120. mL
E The average speed of the hydrogen molecules is the same as the average speed of the oxygen molecules.
Two flexible containers for gases are at the same temperature and pressure. One holds 0.50 gram of hydrogen and the other holds 8.0 grams of oxygen. Which of the following statements regarding these gas samples is FALSE? A The volume of the hydrogen container is the same as the volume of the oxygen container. B The number of molecules in the hydrogen container is the same as the number of molecules in the oxygen container. C The density of the hydrogen sample is less than that of the oxygen sample. D The average kinetic energy of the hydrogen molecules is the same as the average kinetic energy of the oxygen molecules. E The average speed of the hydrogen molecules is the same as the average speed of the oxygen molecules.
B Orange; because the color is orange since it corresponds to wavelengths in the range of 585−647nm585−647nm. The wavelength λλ of the light is 600nm
Using the wavelength information provided above, what is the color of the light? A Red B Orange C Yellow D Blue
C 62.5mL62.5mL
What volume of a 0.100MHCl stock solution should be used to prepare 250.00mL of 0.0250MHCl? A 1.00mL1.00mL B 16.0mL16.0mL C 62.5mL62.5mL D 100.mL
B 4.0 atm
When 6.0 L of He(g) and 10. L of N2(g), both at 0oC and 1.0 atm, are pumped into an evacuated 4.0 L rigid container, the final pressure in the container at 0oC is... A 2.0 atm B 4.0 atm C 6.4 atm D 8.8 atm E 16 atm
B The pressure of the gas
When a sample of oxygen gas in a closed container of constant volume is heated until its absolute temperature is doubled, which of the following is also doubled? A The density of the gas B The pressure of the gas C The average velocity of the gas molecules D The number of molecules per cm3 E The potential energy of the molecules
C Gas ZZ has a smaller molar mass than gas XX.
A The molecules of gas ZZ have a higher average kinetic energy than the molecules of gas XX. B There are fewer molecules in the sample of gas ZZ than in the sample of gas XX. C Gas ZZ has a smaller molar mass than gas XX. D Gas ZZ has a greater molar mass than gas XX.
(d) The average kinetic energy of the helium atoms and neon atoms do not change when the gases are combined.
A 1 L sample of helium gas at 25ºC and 1 atm is combined with 1 L sample of neon gas at 25ºC and 1 atm. The temperature is kept constant. Which of the following statements about combining gases is correct? (a) The average speed of the helium atoms increases when the gases are combined. (b) The average speed of the neon atoms increases when the gases are combined. (c) The average kinetic energy of the helium atoms increases when the gases are combined. (d) The average kinetic energy of the helium atoms and neon atoms do not change when the gases are combined.
C are attracted to each other and do not exert as much force on the container walls as they would if they had no mutual attractions
A 1.0 L sample of a pure gas is found to have a lower pressure than that predicted by the ideal gas law. The best explanation for the observation is that the molecules of the gas A have a combined volume that is too large to be considered negligible when compared to the volume of the container B have a low molecular mass and therefore do not strike the container walls with as much force as expected C are attracted to each other and do not exert as much force on the container walls as they would if they had no mutual attractions D are attracted to the sides of the container and strike the container walls with more force than expected
D 1.0M1.0M
A 500.mL aqueous solution of Na3PO4 (molarmass=164g/mol) was prepared using 82gof the solute. What is the molarity of Na3PO4 in the resulting solution? A 0.0010M0.0010M B 0.16M0.16M C 0.25M0.25M D 1.0M1.0M
(e) a molecular solid
A certain crystalline substance that has a low melting point does not conduct electricity in solution or when melted. This substance is likely to be... (a) a covalent network solid (b) a metallic solid (c) a polymer (d) an ionic solid (e) a molecular solid
(e) 160 mm Hg
A flask contains 0.25 mole of SO2(g), 0.50 mole CH4(g), and 0.50 mole of 02(g). The total pressure of the gases in the flask is 800 mm Hg. What is the partial pressure of the SO2(g) in the flask? (a) 800 mm Hg (b) 600 mm Hg (c) 250 mm Hg (d) 200 mm Hg (e) 160 mm Hg
B About 12atm12atm, because the volume of the gas mixture decreased by a factor of 12.
A gaseous air‑fuel mixture in a sealed car engine cylinder has an initial volume of 600.mL at 1.0atm. To prepare for ignition of the fuel, a piston moves within the cylinder, reducing the volume of the air‑fuel mixture to 50.mL at constant temperature. Assuming ideal behavior, what is the new pressure of the air‑fuel mixture? A About 0.083atm0.083atm, because the initial volume of the gas mixture was 12 times larger than its final volume. B About 12atm12atm, because the volume of the gas mixture decreased by a factor of 12. C About 120.atm120.atm, because the initial volume of the gas mixture was 120 times larger than its final volume. D About 550.atm550.atm, because the change in the volume of the gas mixture was 550.mL550.mL.
E mass of the water in the apparatus
A sample of an unknown gas from a cylinder is collected over water in the apparatus shown above. After all the gas sample has been collected, the water levels inside and outside the gas collection tube are made the same. Measurements that must be made to calculate the molar mass of the gas include all of the following EXCEPT... atmospheric pressure B temperature of the water C volume of gas in the gas-collection tube D initial and final mass of the gas cylinder E mass of the water in the apparatus
(b) The average molecular speed of ethane is greater than the average molecular speed of propanol; because ethane molecules are less massive than propanol molecules, in order to have the same kinetic energy (as they do in the graph), the average speed of ethan molecules must be faster than that if propanol molecules.
A sealed 10.0L flask at 400K contains equimolar amounts of ethane and propanol in gaseous form. Which of the following statements concerning the average molecular speed of ethane and propanol is true? (a) The average molecular speed of ethane is less than the average molecular speed of propanol. (b) The average molecular speed of ethane is greater than the average molecular speed of propanol. (c) The average molecular speed of ethane is equal to the average molecular speed of propanol. (d) The average molecular speeds of ethane and propanol cannot be compared without knowing the total pressure of the gas mixture.
C The particle is a positive ion, and the interactions are ion-dipole attractions.
A solid compound of a group 1 (alkali) metal and a group 17 (halogen) element dissolves in water. The diagram above represents one type of solute particle present in the solution. Which of the following identifies the solute particle and best helps explain how the solute particle interacts with water molecules? A The particle is a negative ion, and the interactions are hydrogen bonds. B The particle is a negative ion, and the interactions are ion-dipole attractions. C The particle is a positive ion, and the interactions are ion-dipole attractions. D The particle is a positive ion, and the interactions are dipole-dipole attractions.
A The increase in conductivity indicates that the unknown is an ionic solid that dissociates into ions when it dissolves in water.
A student adds a 1g sample of an unknown, brittle solid to distilled water, stirs the mixture, and then measures its conductivity. The student repeats this procedure with more samples of the unknown solid and then produces the graph above. Which of the following statements about the graph and the properties of the solid is correct? A The increase in conductivity indicates that the unknown is an ionic solid that dissociates into ions when it dissolves in water. B The increase in conductivity indicates that the unknown is a network covalent solid that ionizes in water. C The straight line plot indicates that the unknown solid is infinitely soluble in water. D The straight line plot indicates that the unknown solid has a very low solubility in water.
(d) Testing the electrical conductivity of an aqueous solution of the substance
A student is given a sample of a pure, white crystalline substance. Which of the following would be most useful in providing data to determine if the substance is an ionic compound? (a) Examining the crystals of the substance under a microscope (b) Determining the density of the substance (c) Testing the electrical conductivity of the crystals (d) Testing the electrical conductivity of an aqueous solution of the substance
B The measured absorbance of the FeSCN2+FeSCN2+ solution will be higher than the actual absorbance.
A student measures the absorbance of a solution containing FeSCN2+ ion using a spectrophotometer. The cuvette used by the student has two frosted walls and two transparent walls. The student properly orients the cuvette so that the path of the light goes through the transparent sides of the cuvette when calibrating the spectrophotometer. How will the measured absorbance of the FeSCN2+ be affected if the student incorrectly orients the cuvette so that the path of the light is through the frosted sides of the cuvette? A The measured absorbance of the FeSCN2+FeSCN2+ solution will not be affected. B The measured absorbance of the FeSCN2+FeSCN2+ solution will be higher than the actual absorbance. C The measured absorbance of the FeSCN2+FeSCN2+ solution will be lower than the actual absorbance. D The effect on the measured absorbance of the FeSCN2+FeSCN2+ solution depends on the concentration of the FeSCN2+FeSCN2+ solution.
D Distillation, because the liquids would boil at different temperatures owing to the difference in strength of their intermolecular forces; because the difference in boiling points between the two liquids would permit their separation by the process of distillation. In the vapor above a heated mixture of the two liquids, the compound with the lower boiling point (hexane) would predominate. When that vapor cools as it passes through a condenser, liquid hexane could be collected.
A student obtains a mixture of the liquids hexane and octane, which are miscible in all proportions. Which of the following techniques would be best for separating the two components of the mixture, and why? A Filtration, because the different densities of the liquids would allow one to pass through the filter paper while the other would not. B Paper chromatography, because the liquids would move along the stationary phase at different rates owing to the difference in polarity of their molecules. C Column chromatography, because the higher molar mass of octane would cause it to move down the column faster than hexane. D Distillation, because the liquids would boil at different temperatures owing to the difference in strength of their intermolecular forces.
A The measured absorbance would be too low, because the distilled water left in the cuvette would slightly dilute the solution.
A student uses a spectrophotometer to analyze a solution of blue food dye. The student first rinses a cuvette with distilled water. Then the student adds the blue dye solution to the cuvette, forgetting to rinse the cuvette with the blue dye solution first. The student places the cuvette in the spectrophotometer and measures the absorbance of the solution. Assuming that some distilled water droplets were still in the cuvette when the blue dye solution was added, how would the measured absorbance be affected? A The measured absorbance would be too low, because the distilled water left in the cuvette would slightly dilute the solution. B The measured absorbance would be too low, because the distilled water would change the optimum wavelength of absorbance. C The measured absorbance would be too high, because the water would allow more light to pass through the cuvette. D The measured absorbance would be too high, because the distilled water would also absorb some light.
A 0.200M
A student uses visible spectrophotometry to determine the concentration of CoCl2(aq) in a sample solution. First the student prepares a set of CoCl2(aq) solutions of known concentration. Then the student uses a spectrophotometer to determine the absorbance of each of the standard solutions at a wavelength of 510nm and constructs a standard curve. Finally, the student determines the absorbance of the sample of unknown concentration. The original solution used to make the solutions for the standard curve was prepared by dissolving 2.60g of CoCl2 (molar mass 130.g/mol) in enough water to make 100.mL of solution. What is the molar concentration of the solution? A 0.200M B 0.500M C 1.00M D 5.00M
B 42.8 grams of KIO3 and add H2O until the final homogeneous solution has a volume of 2.00 liters
A student wishes to prepare 2.00 liters of 0.100-molar KIO3 (molecular weight 214). The proper procedure is to weigh out A 42.8 grams of KIO3 and add 2.00 kilograms of H2O B 42.8 grams of KIO3 and add H2O until the final homogeneous solution has a volume of 2.00 liters C 21.4 grams of KIO3 and add H2O until the final homogeneous solution has a volume of 2.00 liters D 42.8 grams of KIO3 and add 2.00 liters of H2O E 21.4 grams of KIO3 and add 2.00 liters of H2O
(d) 4 x 10^-19 J
A wavelength of 510 nm corresponds to an approximate frequency pf 6 x 10^14s^-1. What is the approximate energy of one photon of this light? (a) 9 x 10^47 J (b) 3 x 10^17 J (c) f x 10^-7 J (d) 4 x 10^-19 J
B 2.3atm2.3atm, because the pressure PP increases by the proportion 313283313283.
At 10.°C, 20.g of oxygen gas exerts a pressure of 2.1atm in a rigid, 7.0L cylinder. Assuming ideal behavior, if the temperature of the gas was raised to 40.°C, which statement indicates the new pressure and explains why? A 1.9atm1.9atm, because the pressure PP decreases by the proportion 283313283313. B 2.3atm2.3atm, because the pressure PP increases by the proportion 313283313283. C 0.52atm0.52atm, because the pressure PP decreases by the proportion 10.40.10.40.. D 8.4atm8.4atm, because the pressure PP increases by the proportion 40.10.40.10..
(a) forces among Br2 molecules are stronger than those among Cl2 molecules
At 298 K and 1 atm, Br2 is a liquid with a high vapor pressure, and CL2 is a gas. Those observations provide evidence that, under the given conditions, the... (a) forces among Br2 molecules are stronger than those among Cl2 molecules (b) forces among Cl2 molecules are stronger than the Cl−Cl bond (c) Br−Br bond is stronger than the Cl−Cl bond (d) Cl−Cl bond is stronger than the Br−Br bond
C It depends on the relative molecular masses of X, Y, and
Equal masses of three different ideal gases, X, Y, and Z, are mixed in a sealed rigid container. If the temperature of the system remains constant, which of the following statements about the partial pressure of gas X is correct? A It is equal to ⅓ the total pressure B It depends on the intermolecular forces of attraction between molecules of X, Y, and Z. C It depends on the relative molecular masses of X, Y, and Z. D It depends on the average distance traveled between molecular collisions. E It can be calculated with knowledge only of the volume of the container.
B C2H6C2H6 molecules have a larger, more polarizable electron cloud than CH4CH4 molecules do.
Equimolar samples of CH4(g) and C2H6(g) are in identical containers at the same temperature. The C2H6(g) deviates much more from ideal behavior than the CH4(g) does. Which of the following best helps explain this deviation? A C2H6C2H6 molecules have more hydrogen bonding than CH4CH4 molecules do. B C2H6C2H6 molecules have a larger, more polarizable electron cloud than CH4CH4 molecules do. C The C2H6C2H6 molecules have a greater average kinetic energy than the CH4CH4 molecules have. D The C2H6C2H6 molecules have a greater average speed than the CH4CH4 molecules have.
(d) 100 mL volumetric flask
For an experiment, a student needs 100.0 mL of 0.4220 M NaCl. If the student starts with NaCl(s) and distilled water, which of the following pieces of laboratory glassware should the student use to prepare the solution with the greatest accuracy? (a) 25 mL volumetric pipet (b) 100 mL Erlenmeyer flask (c) 100 mL graduated cylinder (d) 100 mL volumetric flask (e) 1 L beaker
(a) 0.555 g
How many grams of CaCl2 (molar mass = 111g/mol) are needed to prepare 100 M Cl- (aq) ions? (a) 0.555 g (b) 1.11 g (c) 2.22 g (d) 5.55 g
D 1.5g1.5g
How many grams of NaCl (molarmass=58g/mol) are needed to prepare 100.mL of a 0.25M NaCl solution? A 0.23g0.23g B 0.43g0.43g C 0.67g0.67g D 1.5g1.5g
(b) The energies of infrared photons are in the same range as the energies associated with different vibrational states of chemical bonds. Molecules can absorb infrared photons of characteristic wavelengths, thus revealing types and strengths of different bonds in the molecules.
Infrared spectroscopy is a useful tool for scientists who want to investigate the structure of certain molecules. Which of the following best explains what can occur as the result of a molecule absorbing a photon of infrared radiation? (a) The energies of infrared photons are in the same range as energies associated with changes between different electronic energy states in atoms and molecules. Molecules can absorb infrared photons of characteristic wavelengths, thus revealing the energies of electronic transitions within the molecules. (b) The energies of infrared photons are in the same range as the energies associated with different vibrational states of chemical bonds. Molecules can absorb infrared photons of characteristic wavelengths, thus revealing types and strengths of different bonds in the molecules. (c) The energies of infrared photons are in the same range as the energies associated with different rotational states of molecules. Molecules can absorb infrared photons of characteristic wavelengths, thus revealing the energies of transition between different rotational energy states of the molecules. (d) The energies of infrared photons are in the same range as the total bond energies of bonds within molecules. Chemical bonds can be completely broken as they absorb infrared photons of characteristic wavelengths, thus revealing the energies of the bonds within the molecules.
B KNO3
On the basis of the solubility curves shown above, the greatest percentage of which compound can be recovered by cooling a saturated solution of that compound from 90°C to 30°C? A NaCl B KNO3 C K2CrO4 D K2SO4 E Ce2(SO4)3
A The absorption of infrared radiation causes the nonbonding electrons on oxygen to transition into a higher electronic energy level.
One type of organic molecule can be converted to another type of organic molecule through an oxidation-reduction process, as represented in the diagram above. Which of the following best explains why infrared spectroscopy is an appropriate method to confirm that the product contains a carbonyl? A The absorption of infrared radiation causes the nonbonding electrons on oxygen to transition into a higher electronic energy level. B The absorption of infrared radiation leads to an increase in molecular vibrational level associated with the stretching of the carbonyl. C The absorption of infrared radiation causes the electrons in the pi bond to transition to a higher bonding energy level. D Infrared radiation leads to an increase in the molecular rotational level associated with the carbonyl as the axis of rotation.
B greatest in container B; because all three containers are at the same temperature, the number of particles per unit volume is directly proportional to the pressure. The density is the mass per unit volume, so the density is proportional to the product of the pressure and the molar mass. This product is greatest for container B.
Questions refer to three gases in identical rigid containers under the conditions given in the table below. A greatest in container A B greatest in container B C greatest in container C D the same in all three containers
(b) CCl4
Sodium chloride is LEAST soluble in which of the following liquids? (a) H2O (b) CCl4 (c) HF (d) CH3OH (e) CH3COOH
B 0.033 M
Solid Al(NO3)3 is added to distilled water to produce a solution in which the concentration of nitrate, [NO3-], is 0.10 M. What is the concentration of aluminum ion, [Al3+], in this solution? A 0.010 M B 0.033 M C 0.066 M D 0.10 M E 0.30 M
(c) intermolecular attractions resulting from temporary dipoles
Solid carbon tetrachloride, CCl4 , is represented by the diagram above. The attractions between the CCL4 molecules that hold the molecules together in the solid state are best identified as (a) polar covalent bonds (b) nonpolar covalent bonds (c) intermolecular attractions resulting from temporary dipoles (d) intermolecular attractions resulting from permanent dipoles
D Crystalline NaBrNaBr contains no freely moving electrons to conduct electricity, but molten NaBrNaBr is composed of freely moving Na+Na+ and Br−Br− ions, which allows it to be a good conductor of electricity.
The crystal structure of NaBr is represented in the diagram above. Which statement correctly compares crystalline NaBr(s) to molten NaBr(l) in terms of electrical conductivity? A Crystalline NaBrNaBr contains no freely moving electrons that could conduct an electrical current, whereas electrons can flow freely in molten NaBrNaBr, which is a good conductor of electricity. B Crystalline NaBrNaBr and molten NaBrNaBr both contain ions that are held in fixed positions due to strong electrostatic attractions among the ions, making neither a good electrical conductor. C Crystalline NaBrNaBr and molten NaBrNaBr both contain NaNa atoms that transfer electrons to BrBr atoms in a chemical reaction, thus allowing them both to be good conductors of electricity. D Crystalline NaBrNaBr contains no freely moving electrons to conduct electricity, but molten NaBrNaBr is composed of freely moving Na+Na+ and Br−Br− ions, which allows it to be a good conductor of electricity.
C 5.0×1014s−15.0×1014s−1; because the energy of a photon is related to the frequency ν of the electromagnetic wave according to Planck's equation (E=hν). If the energy EE is divided by Planck's constant hh, the frequency is 5×1014s−15×1014s−1.
The diagram above represents the photoelectric effect for a metal. When the metal surface is exposed to light with increasing frequency and energy of photons, electrons first begin to be ejected from the metal when the energy of the photons is 3.3×10−19J3.3×10−19J. Which of the following is closest to the frequency of the light with photon energy of 3.3×10−19J3.3×10−19J? A 5.0×10−53s−15.0×10−53s−1 B 5.0×10−16s−15.0×10−16s−1 C 5.0×1014s−15.0×1014s−1 D 5.0×1052s−15.0×1052s−1
B Allotrope IIII, because it has covalent bonds between the phosphorous atoms that are stronger than the dispersion forces between the P4P4 molecules in allotrope II.
The diagrams above represent two allotropes of solid phosphorus. Which of the following correctly identifies the allotrope with the higher melting point and explains why? A Allotrope II, because it has P4P4 molecules with covalent bonds that are stronger than dispersion forces between individual PP atoms in allotrope IIII. B Allotrope IIII, because it has covalent bonds between the phosphorous atoms that are stronger than the dispersion forces between the P4P4 molecules in allotrope II. C Allotrope IIII, because it has metallic bonding that is stronger than the covalent bonding found in the P4P4 molecules in allotrope II. D Both allotropes have the same melting point because they both contain phosphorous atoms.
B The gas in sample 2 would deviate more from ideal behavior because the Xe atoms are closer together, leading to an increase in intermolecular attractions; because the molecules are, on average, closer together, leading to a larger impact from the intermolecular attractive forces, which increase as distance between the molecules decreases.
The diagrams above represent two samples of Xe gas in containers of equal volume at 280K. Which of the following correctly compares the two samples in terms of their deviation from ideal gas behavior and explains why? (sample 1 = 4 random dots; sample 2 = 8 random dots) The gas in sample 1 would deviate more from ideal behavior because the average distance an Xe atom travels before colliding with another Xe atom is greater. B The gas in sample 2 would deviate more from ideal behavior because the Xe atoms are closer together, leading to an increase in intermolecular attractions. C The gas in sample 2 would deviate more from ideal behavior because the average speed of the XeXe atoms is less, leading to an increase in intermolecular attractions. D The gases in both sample 1 and sample 2 would show the same deviation from ideal behavior
D Diagram 2, because the particles have a variety of different speeds.
The diagrams above use arrows to represent the speed of a gas particle. Which of the diagrams best represents the speed of the particles of a gas at a fixed temperature, and why? A Diagram 1, because all the particles have the same speed. B Diagram 1, because the particles are moving in different directions. C Diagram 2, because the particles have a net kinetic energy of zero. D Diagram 2, because the particles have a variety of different speeds.
(a) dotted line is first and highest; solid line is last and lower
The distribution of speeds of H2(g) molecules at 273 K and 1 atm is shown in the diagram above (a little hump that goes up then back down gradually). Which of the following best shows the speed distribution of He(g) atoms under the same conditions of temperature and pressure? (a) dotted line is first and highest; solid line is last and lower (b) dotted line is last and highest; solid line is first and lower (c) both equal height and distance from y-axis (d) both equal height; dotted line is slightly further than solid line
(d) Liquid F2 has weak dispersion force attractions between its molecules, whereas liquid HF has both weak dispersion force attractions and hydrogen bonding interactions between its molecules; because the hydrogen bonding interactions in HFHF are much stronger than the weak dispersion forces between F2F2 molecules.
The electron cloud of HF is smaller than that of F2 , however, HF has a much higher boiling point than F2 has. Which of the following explains how the dispersion-force model of intermolecular attraction does not account for the unusually high boiling point of HF? (a) F2 is soluble in water, whereas HFHF is insoluble in water. (b) The F2 molecule has a greater mass than the HFHF molecule has. (c) Liquid F2 has weak dispersion force attractions between its molecules, whereas liquid HFHF has strong ionic interactions between H+ and F− ions. (d) Liquid F2 has weak dispersion force attractions between its molecules, whereas liquid HF has both weak dispersion force attractions and hydrogen bonding interactions between its molecules.
(a) Intermolecular attractions are completely overcome during vaporization.
The following questions refer to the graph below, which shows the heating curve for methane, CH4. (graph) Which of the following best explains why more energy is required for the process occurring at 110 K than for the process occurring at 90 K ? (a) Intermolecular attractions are completely overcome during vaporization. (b) Intermolecular attractions in the solid phase are weaker than in the liquid phase. (c) Electron clouds of methane molecules are less polarizable at lower temperatures. (d) Vaporization involves a large increase in temperature.
C 4×10−19J4×10−19J
The frequency and energy ranges of photons in some parts of the electromagnetic spectrum are given in the table above. Which of the following could be the energy of a photon in the visible range? A 9×10−21J9×10−21J B 4×10−20J4×10−20J C 4×10−19J4×10−19J D 9×10−19J
D CO2CO2 is a nonpolar molecule that has London dispersion intermolecular forces that are weaker than the dipole-dipole and London dispersion forces between the polar NH3NH3 molecules.
The gases CO2(g) and NH3(g) can be liquefied at 20°C by compressing them to sufficiently high pressures. A student claims that NH3(g) can be liquefied at a lower pressure than CO2(g) can be liquefied. Which of the following is the best justification for this claim? A At 20°C20°C, the average speed of NH3NH3 molecules is greater than that of CO2CO2 molecules because NH3NH3 molecules have less mass than CO2CO2 molecules have. B CO2CO2 is a nonpolar molecule that has no significant intermolecular forces, whereas NH3NH3 has strong London dispersion intermolecular forces. C Both CO2CO2 and NH3NH3 are nonpolar molecules that have only London dispersion intermolecular forces, but the larger electron cloud of CO2CO2 molecules causes it to have stronger intermolecular forces. D CO2CO2 is a nonpolar molecule that has London dispersion intermolecular forces that are weaker than the dipole-dipole and London dispersion forces between the polar NH3NH3 molecules.
A The atoms in the CO2CO2 molecules increase their vibration as the bonds between the atoms bend and stretch.
The infrared spectrum above represents the absorption of certain wavelengths of radiation by molecules of CO2. Which of the following best explains what occurs at the molecular level as the CO2 molecules absorb photons of the infrared radiation? A The atoms in the CO2CO2 molecules increase their vibration as the bonds between the atoms bend and stretch. B The molecules of CO2CO2 increase the energy of their rotational motions. C The electrons in the valence shells of the atoms in the CO2CO2 molecules are promoted to higher electronic energy levels. D The bonds between the atoms in the CO2CO2 molecules are continuously broken and then re-form.
C Carbon atoms in diamond have four covalent bonds, whereas graphite is made of layers that are held together by relatively weak dispersion forces.
The structures of two allotropes of carbon are represented above. Which of the following statements best helps explain why diamond is much harder than graphite? A Diamond contains covalent bonds, whereas graphite contains ionic bonds. B Diamond contains ionic bonds, whereas graphite contains covalent bonds. C Carbon atoms in diamond have four covalent bonds, whereas graphite is made of layers that are held together by relatively weak dispersion forces. D Carbon atoms in diamond have a sea of mobile electrons that make the structure strong, whereas graphite does not contain delocalized electrons.
A The total pressure of the gases in the mixture is the sum of the initial pressures of oxygen gas and nitrogen gas because pressure only depends on the total amount of gas when volume and temperature are held constant.
Two sealed, rigid 5.0L containers each contain a gas at the same temperature but at a different pressure, as shown above. Also shown are the results of transferring the entire contents of container 1 to container 2. No gases escape during the transfer. Assuming ideal behavior, which statement is correct regarding the total pressure of the gases after they are combined? A The total pressure of the gases in the mixture is the sum of the initial pressures of oxygen gas and nitrogen gas because pressure only depends on the total amount of gas when volume and temperature are held constant. B The total pressure of the gases in the mixture is lower than the sum of the initial pressures of oxygen and nitrogen because some of the energy of the particles will be lost due to an increase in the number of collisions. C The total pressure of the gases in the mixture is higher than the sum of the initial pressures of oxygen and nitrogen because of the intermolecular forces that develop between oxygen and nitrogen molecules. D The total pressure of the gases in the mixture cannot be determined because the actual value of the temperature is not given.
C Temperature(K) = 800; Pressure(atm) = 0.1
Under which of the following conditions of temperature and pressure would 1.0 mol of the real gas CO2(g) behave most like an ideal gas? A Temperature(K) = 100; Pressure(atm) = 0.1 B Temperature(K) = 100; Pressure(atm) = 100 C Temperature(K) = 800; Pressure(atm) = 0.1 D Temperature(K) = 800; Pressure(atm) = 1 E Temperature(K) = 800; Pressure(atm) = 100
B Distillation
When methanol and water are mixed together, they form a homogeneous mixture. Based on the information in the table above, which of the following would be the best procedure for separating a mixture of methanol and water? A Filtration B Distillation C Paper chromatography D Column chromatography
A Diagram 1, because strong ion-dipole interactions between KClKCl and water help to dissociate the solute.
Which of the diagrams above best represents the interactions that are responsible for the relatively large solubility of KCl crystals in water, and why? A Diagram 1, because strong ion-dipole interactions between KClKCl and water help to dissociate the solute. B Diagram 1, because strong London dispersion forces between the K+K+ and Cl−Cl− ions and water replace the weak London dispersion forces between two water molecules. C Diagram 2, because strong dipole-dipole forces between KClKCl and water help to separate the KClKCl units within the crystals. D Diagram 2, because the hydrogen bonds between water molecules expand to accommodate the KClKCl particles and pull them into solution.
A Certain electrons in the dye molecule move to a higher energy level, with the difference in energy between the lower and higher energy levels being the same as the energy of the absorbed photons.
Which of the following best explains what happens as photons of visible light are absorbed by dye molecules? A Certain electrons in the dye molecule move to a higher energy level, with the difference in energy between the lower and higher energy levels being the same as the energy of the absorbed photons. B Certain chemical bonds in the dye molecules begin to bend and stretch, with the difference in energy between the lower and higher vibrational states being the same as the energy of the absorbed photons. C The dye molecules begin to rotate faster in certain modes, with the difference in energy between the lower and higher rotational states being the same as the energy of the absorbed photons. D Certain covalent bonds in the dye molecules begin to break and re-form, with the bond energies of the bonds being the same as the energy of the absorbed photons.
(d) The London dispersion forces are stronger in CI4 than in CCl4 because CI4 has a more polarizable electron cloud than CCl4
Which of the following best helps to explain why CCl4 is a liquid whereas CI4 is a solid when both are at 25°C? (a) The dipole moment of the CCl4 molecule is larger than that of the CI4 molecule because Cl is more electronegative than I. (b) The dipole moment of the CI4 molecule is larger than that of the CCl4 molecule because there is stronger repulsion between electrons in the C-I bonds compared to the repulsion between electrons in the C- Cl bonds. (c) The London dispersion forces are stronger in CCl4 than in CI4 because Cl is more electronegative than I. (d) The London dispersion forces are stronger in CI4 than in CCl4 because CI4 has a more polarizable electron cloud than CCl4
(d) Spectrophotometry
Which of the following experimental techniques will allow the most accurate determination of the concentration of NO2(g) at equilibrium between a brown liquid and a clear liquid? (a) Paper chromatography (b) Gravimetric analysis (c) Titration (d) Spectrophotometry
D Paper chromatography using different solvents with a range of polarities as the mobile phase
Which of the following methods is most appropriate to use to determine the number of different-colored components in a sample of black ink? A Distillation at atmospheric pressure B Elemental analysis to determine the mass ratio of C:H:N:OC:H:N:O C Column chromatography using a nonpolar stationary phase and water as the mobile phase D Paper chromatography using different solvents with a range of polarities as the mobile phase
B 25 mL pipet
Which of the following pieces of laboratory glassware should be used to most accurately measure out a 25.00 mL sample of a solution? A 5 mL pipet B 25 mL pipet C 25 mL beaker D 25 mL Erlenmeyer flask E 50 mL graduated cylinder
(b) HF, because its molecules form hydrogen bonds
Which of the following substances listed has the highest boiling point, and why? Ne, HF, C2H6, CH4 (a) Ne, because its atoms have the largest radius (b) HF, because its molecules form hydrogen bonds (c) C2H6, because each molecule can form multiple hydrogen bonds (d) CH4, because its molecules have the greatest London Dispersion forces.
E Evaporation to dryness
Which of the following techniques is most appropriate for the recovery of solid KNO3 from an aqueous solution of KNO3? A Paper chromatography B Filtration C Titration D Electrolysis E Evaporation to dryness
C Diagram 2, because it shows the formation of a hydrogen bond between an HH atom bonded to an OO atom with an OO atom from another molecule.
Which particle diagram shown above best represents the strongest intermolecular force between two ethanol, C2H6O, molecules? A Diagram 1, because it shows hydrogen bonds forming between hydrogen atoms from different ethanol molecules. B Diagram 1, because it shows strong, directional dipole-dipole forces between two polar ethanol molecules. C Diagram 2, because it shows the formation of a hydrogen bond between an HH atom bonded to an OO atom with an OO atom from another molecule. D Diagram 2, because it shows the dipole from an ethanol molecule inducing a dipole in another ethanol molecule.
