Chemistry - Unit 3 - Joseph
Which of the following gases deviates most from ideal behavior? 3.6 MC Questions
A SO2 B Ne C CH4 D N2 E H2
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? 3.11 MC Questions
A The energies of infrared photons are in the same range as the 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 the 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.
A vessel contains Ar(g) at a high pressure. Which of the following statements best helps to explain why the measured pressure is significantly greater than the pressure calculated using the ideal gas law? 3.6 MC Questions
A The molar mass of Ar is relatively large. B A significant number of Ar2 molecules form. C The attractive forces among Ar atoms cause them to collide with the walls of the container with less force. D The combined volume of the Ar atoms is too large to be negligible compared with the total volume of the container.
The compound urea, H2 NCONH2 , is widely used in chemical fertilizers. The complete Lewis electron-dot diagram for the urea molecule is shown above. Urea has a high solubility in water, due in part to its ability to form hydrogen bonds. 3.8 & 3.10 FRQ
A urea molecule and four water molecules are represented in the box below. Draw ONE dashed line (----) to indicate a possible location of a hydrogen bond between a water molecule and the urea molecule.
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? 3.7 MC Questions
A) 0.010 M B) 0.033 M C) 0.066 M D) 0.10 M E) 0.30 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 3.7 MC Questions
A) 0.025 M B) 0.050 M C) 0.10 M D) 0.50 M E) 1.0 M
What is the molarity of I- (aq) in a solution that contains 34 g of SrI2 (molar mass 341 g) in 1.0 L of the solution? 3.7 MC Questions
A) 0.034 M B) 0.068 M C) 0.10 M D) 0.20 M E) 0.68 M
Given that the density of Hg(l) at 0°C is about 14 g mL-1 , which of the following is closest to the volume of one mole of Hg(l) at this temperature? 3.4 MC Questions
A) 0.070 mL B) 0.14 mL C) 1.4 mL D) 14 mL E) 28 mL
A 360 mg sample of aspirin, C9 H8 O4 , (molar mass 180 g), is dissolved in enough water to produce 200 mL of solution. What is the molarity of aspirin in a 50 mL sample of this solution? 3.7 MC Questions
A) 0.080 M B) 0.040 M C) 0.020 M D) 0.010 M E) 0.0025 M
A 40.0 mL sample of 0.25 M KOH is added to 60.0 mL of 0.15 M Ba(OH)2 . What is the molar concentration of OH- (aq) in the resulting solution? (Assume that the volumes are additive.) 3.7 MC Questions
A) 0.10 M B) 0.19 M C) 0.28 M D) 0.40 M E) 0.55 M
A 0.20 mol sample of MgCl2(s)and a 0.10 mol sample of KCl(s)are dissolved in water and diluted to 500 mL. What is the concentration of Cl- in the solution? 3.7 MC Questions
A) 0.15 M B) 0.30 M C) 0.50 M D) 0.60 M E) 1.00 M
If 200. mL of 0.60 M MgCl2(aq) is added to 400. mL of distilled water, what is the concentration of Mg2+ (aq) in the resulting solution? (Assume volumes are additive). 3.7 MC Questions
A) 0.20 M B) 0.30 M C) 0.40 M D) 0.60 M E) 1.2 M
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? 3.7 MC Questions
A) 0.200 M B) 0.500 M C) 1.00 M D) 5.00 M
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 3.4 MC Questions
A) 0.200 atm B) 0.500 atm C) 1.000 atm D) 2.000 atm E) 5.000 atm
How many moles of Na+ ions are in 100.mL of 0.100M Na3 PO4(aq) ? 3.7 MC Questions
A) 0.300 mol B) 0.100 mol C) 0.0300 mol D) 0.0100 mol
When 4.0 L of He(g), 6.0 L of N2(g), and 10. L of Ar(g), all at 0°C and 1.0 atm, are pumped into an evacuated 8.0 L rigid container, the final pressure in the container at 0°C is 3.4 MC Questions
A) 0.5 atm B) 1.0 atm C) 2.5 atm D) 4.0 atm
How many grams of CaCl2 (molar mass =111g/mol) are needed to prepare 100 mL of 0.100MCl− (aq) ions? 3.7 MC Questions
A) 0.555 g B) 1.11 g C) 2.22 g D) 5.55 g
An equimolar mixture of N2(g) and Ar(g) is kept inside a rigid container at a constant temperature of 300 K. The initial partial pressure of Ar in the mixture is 0.75atm. An additional amount of Ar was added to the container, enough to double the number of moles of Ar gas in the mixture. Assuming ideal behavior, what is the final pressure of the gas mixture after the addition of the Ar gas? 3.4 MC Questions
A) 0.75 atm, because increasing the partial pressure of Ar decreases the partial pressure of N2 . B) 1.13 atm, because 33% of the moles of gas are N2 . C) 1.50 atm, because the number of moles of N2 did not change. D) 2.25 atm, because doubling the number of moles of Ar doubles its partial pressure.
A 2 L sample of N2(g) and a 1 L sample of Ar(g), each originally at 1 atm and 0°C, are combined in a 1 L tank. If the temperature is held constant, what is the total pressure of the gases in the tank? 3.4 MC Questions
A) 1 atm B) 2 atm C) 3 atm D) 4 atm E) 5 atm
Equal masses of He and Ne are placed in a sealed container. What is the partial pressure of He if the total pressure in the container is 6 atm? 3.4 MC Questions
A) 1 atm B) 2 atm C) 3 atm D) 4 atm E) 5 atm
How many mL of 10.0 M HCl are needed to prepare 500 mL of 2.00 M HCl ? 3.7 MC Questions
A) 1.00 mL B) 10.0 mL C) 20.0 mL D) 100 mL E) 200 mL
The volume of water that must be added in order to dilute 40 mL of 9.0 M HCl to a concentration of 6.0 M is closest to 3.7 MC Questions
A) 10 mL B) 20 mL C) 30 mL D) 40 mL E) 60 mL
A student prepares a solution by dissolving 60.00 g of glucose (molar mass 180.2 g mol-1) in enough distilled water to make 250.0 mL of solution. The molarity of the solution should be reported as 3.7 MC Questions
A) 12.01 M B) 12.0 M C) 1.332 M D) 1.33 M E) 1.3 M
When 70 milliliter of 3.0 molar Na2 CO3 is added to 30 milliliters of 1.0-molar NaHCO3 the resulting concentration of Na+ is 3.7 MC Questions
A) 2.0 M B) 2.4 M C) 4.0 M D) 4.5 M E) 7.0 M
When 6.0 L of He(g) and 10. L of N2(g), both at 0°C and 1.0 atm, are pumped into an evacuated 4.0 L rigid container, the final pressure in the container at 0°C is 3.4 MC Questions
A) 2.0 atm B) 4.0 atm C) 6.4 atm D) 8.8 atm E) 16 atm
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? 3.7 MC Questions
A) 25 mL volumetric pipet B) 100 mL Erlenmeyer flask C) 100 mL graduated cylinder D) 100 mL volumetric flask E) 1 L beaker
Approximately what mass of CuSO4 • 5H2 O (250 g mol-1) is required to prepare 250 mL of 0.10 M copper(II) sulfate solution? 3.7 MC Questions
A) 4.0 g B) 6.2 g C) 34 g D) 85 g E) 140 g
A student wishes to prepare 2.00 liters of 0.100 molar KIO3 (molecular weight 214). The proper procedure is to weigh out 3.7 MC Questions
A) 42.8 grams of KIO3 and add 2.00 kilograms of H2 O 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 H2 O until the final homogeneous solution has a volume of 2.00 liters D) 42.8 grams of KIO3 and add 2.00 liters of H2 O E) 21.4 grams of KIO3 and add 2.00 liters of H2 O
Under which of the following conditions of temperature and pressure will H2 gas be expected to behave most like an ideal gas? 3.6 MC Questions
A) 50 K and 0.10 atm B) 50 K and 5.0 atm C) 500 K and 0.10 atm D) 500 K and 50 atm
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 3.7 MC Questions
A) 50.0 mL B) 60.0 mL C) 100 mL D) 110 mL E) 120 mL
A flask contains 0.25 mole of SO2(g), 0.50 mole of CH4(g), and 0.50 mole of O2(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? (All pressures are mm Hg) 3.4 MC Questions
A) 800 B) 600 C) 250 D) 200 E) 160
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. A wavelength of 510nm corresponds to an approximate frequency of 6 × 1014 s−1. What is the approximate energy of one photon of this light? 3.12 MC Questions
A) 9 × 1047 J B) 3 × 1017 J C) 5 × 10−7 J D) 4 × 10−19 J
A student performed a fractional distillation of a mixture of two straight-chain hydrocarbons, C7 H16 and C8 H18. Using four clean, dry flasks, the student collected the distillate over the volume ranges (A, B, C, and D) shown in the graph above. Over what volume range should the student collect the distillate of the compound with the stronger intermolecular forces? 3.9 MC Questions
A) A B) B C) C D) D
The following question refers to the 1 L flasks shown below. In which flask do the molecules have the greatest average speed? 3.5 MC Questions
A) A B) B C) C D) D E) E
A gas mixture at 0°C and 1.0 atm contains 0.010 mol of H2 , 0.015 mol of O2 , and 0.025 mol of N2 . Assuming ideal behavior, what is the partial pressure of hydrogen gas (H2) in the mixture? 3.4 MC Questions
A) About 0.010 atm, because there is 0.010mol of H2 in the sample. B) About 0.050 atm, because there is 0.050mol of gases at 0°C and 1.0 atm. C) About 0.20 atm, because H2 comprises 20% of the total number of moles of gas. D) About 0.40 atm, because the mole ratio of H2 : O2 : N2 is 0.4 : 0.6 : 1.
Benzene, C6 H6 , 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? 3.7 FRQ
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.
The structure of one form of boron nitride is represented above. This form of boron nitride is one of the hardest substances known. Which of the following best helps explain why boron nitride is so hard? 3.2
A) Boron ions and nitrogen ions are held together by ionic bonds. B) Boron nitride is a network solid of atoms connected by covalent bonds with fixed bond angles. C) Boron nitride is an alloy, and alloys are typically harder than the elements used to make them. D) Boron nitride is a polymer made of long chains of boron atoms and nitrogen atoms held together by london dispersion forces.
Which of the following could be the identity of a white crystalline solid that exhibits the following properties? • It melts at 320°C. • It does not conduct electricity as a solid. • It conducts electricity in an aqueous solution. 3.2
A) C6 H12O6(s) B) NaOH(s) C) SiO2(s) D) Cu(s)
On the basis of molecular structure and bond polarity, which of the following compounds is most likely to have the greatest solubility in water? 3.7 FRQ
A) CH4 B) CCl4 C) NH3 D) PH3
The ionic compounds NaCl and MgS are represented by the diagrams above. Which statement correctly identifies diagram 1 and identifies the compound with the lower melting point, explaining why? 3.2
A) Diagram 1 represents NaCl ; it has a lower melting point than MgS has because the coulombic attractions between the singly charged Na+ ions and the Cl- ions in NaCl are stronger than those between the ions in MgS. B) Diagram 1 represents NaCl ; it has a lower melting point than MgS because the coulombic attractions between its singly charged Na+ ions and the Cl- ions are weaker than those between the ions in MgS. C) Diagram 1 represents MgS ; it has a lower melting point than NaCl because the coulombic attractions between its doubly charged Mg2+ ions and the S2- ions are stronger than those between the ions in NaCl. D) Diagram 1 represents MgS ; it has a lower melting point than NaCl because the coulombic attractions between the doubly charged Mg2+ ions and the S2- ions are weaker than those between the ions in NaCl.
The survival of aquatic organisms depends on the small amount of O2 that dissolves in H2 O. The diagrams below represent possible models to explain this phenomenon. Which diagram provides the better particle representation for the solubility of O2 in H2 O, and why? 3.7 FRQ
A) Diagram 1, because O2 molecules can form hydrogen bonds with the H2 O molecules. B) Diagram 1, because O2 and H2 O are polar molecules that can interact through dipole-dipole forces. C) Diagram 2, because the polar H2 O molecules can induce temporary dipoles on the electron clouds of O2 molecules. D) Diagram 2, because the nonpolar O2 molecules can induce temporary dipoles on the electron clouds of H2 O molecules.
The table above provides some information about two types of steel, both of which are alloys of iron and carbon. Which of the following best helps to explain why high-carbon steel is more rigid than low-carbon steel? 3.2
A) Elemental carbon is harder than elemental iron. B) The additional carbon atoms within the alloy make the high-carbon steel less dense. C) The additional carbon atoms within the alloy increase the thermal conductivity of the high-carbon steel. D) The additional carbon atoms within the alloy make it more difficult for the iron atoms to slide past one another.
A mixture containing equal numbers of moles of ethyl acetate and butyl acetate was separated using distillation. Based on the diagrams shown above, which of the following identifies the substance that would be initially present in higher concentration in the distillate and correctly explains why that occurs? 3.9 MC Questions
A) Ethyl acetate, because it has fewer C-C bonds to break B) Ethyl acetate, because it has a shorter carbon chain and weaker London dispersion forces C) Butyl acetate, because it has more C-C bonds to break D) Butyl acetate, because it has a longer carbon chain and weaker dipole-dipole attractions
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? 3.2
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
In which of the following liquids do the intermolecular forces include dipole-dipole forces? 3.1
A) F2 (l) B) CH4 (l) C) CF4 (l) D) CH2 F2 (l)
The electron cloud of HF is smaller than that of F2 , however, HF has a much higher boiling point than has F2 . Which of the following explains how the dispersion-force model of intermolecular attraction does not account for the unusually high boiling point of HF? 3.1
A) F2 is soluble in water, whereas HF is insoluble in water. B) The F2 molecule has a greater mass than the HF molecule has. C) Liquid F2 has weak dispersion force attractions between its molecules, whereas l iquid HF 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.
Gases generated in a chemical reaction are sometimes collected by the displacement of water, as shown above. Which of the following gases can be quantitatively collected by this method? 3.7 FRQ
A) H2 B) CO2 C) HCl D) SO3 OH E) CH3 COOH
The London (dispersion) forces are weakest for which of the following gases under the same conditions of temperature and pressure? 3.1
A) H2 B) O2 C) Xe D) F2 E N2
Sodium chloride is LEAST soluble in which of the following liquids? 3.7 FRQ
A) H2 O B) CCl4 C) HF D) CH3 OH E) CH3 COOH
A 0.5 mol sample of He(g) and a 0.5 mol sample of Ne(g) are placed separately in two 10.0 L rigid containers at 25°C. Each container has a pinhole opening. Which of the gases, He(g) or Ne(g), will escape faster through the pinhole and why? 3.5 MC Questions
A) He(g) will escape faster because the He(g) atoms are moving at a higher average speed than the Ne(g) atoms. B) Ne(g) will escape faster because its initial pressure in the container is higher. C) Ne(g) will escape faster because the Ne(g) atoms have a higher average kinetic energy than the He(g) atoms. D) Both gases will escape at the same rate because the atoms of both gases have the same average kinetic energy
A sample of an ideal gas is cooled from 50.0°C to 25.0°C 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 3.5 MC Questions
A) I only B) II only C) III only D) I and III E) II and III
The diagram opposite is a molecular model of a gaseous diatomic element that is just above its boiling point. Intermolecular forces between the gas molecules will cause them to condense into the liquid phase if the temperature is lowered. Which of the following best describes how the model is limited in its depiction of the phenomenon? 3.1
A) It does not show how hydrogen bonds are constantly forming, breaking, and reforming, which results in a net force of attraction between the molecules. B) It does not show how the interactions between ions and the induced molecular dipoles result in a net force of attraction between the molecules. C) It does not show how the interacting permanent dipoles of the molecules result in a net force of attraction between the molecules. D) It does not show how the temporary fluctuating dipoles of the molecular electron clouds result in a net force of attraction between the molecules
At room temperature I2(s) is a molecular solid. Which of the following provides a characteristic of I2(s) with a correct explanation? 3.2
A) It has a high melting point because it has weak intermolecular forces. B) It is hard because it forms a three dimensional covalent network. C) It is not a good conductor of electricity because its valence electrons are localized in bonding and nonbonding pairs. D) It is very soluble in water because its molecules are polar.
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? 3.4 MC Questions
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
Based on the diagram above, which of the following best helps to explain why MgO(s) is not able to conduct electricity, but MgO(l) is a good conductor of electricity? 3.2
A) MgO(s) does not contain free electrons, but MgO(l) contains free electrons that can flow. B) MgO(s) contains no water, but MgO(l) contains water that can conduct electricity. C) MgO(s) consists of separate Mg2+ ions and O2− ions, but MgO(l) contains MgO molecules that can conduct electricity. D) MgO(s) consists of separate Mg2+ ions and O2− ions held in a fixed lattice, but in MgO(l) the ions are free to move and conduct electricity.
Which statement correctly compares what occurs when molecules absorb photons in the microwave region with what occurs when molecules absorb photons in the infrared region? 3.11 MC Questions
A) Microwave photons cause the molecules to increase their rotational energy states, whereas infrared photons cause the molecules to increase their vibrational energy states. B) Microwave photons cause electrons in the molecules to increase their electronic energy states, whereas infrared photons cause the molecules to increase their rotational energy states. C) Microwave photons cause the molecules to increase their vibrational energy states, whereas infrared photons cause electrons in the molecules to increase their electronic energy states. D) Microwave photons cause the molecules to increase their rotational energy states, whereas infrared photons cause electrons in the molecules to increase their electronic energy states.
N2 molecules absorb ultraviolet light but not visible light. I2 molecules absorb both visible and ultraviolet light. Which of the following statements explains the observations? 3.11 MC Questions
A) More energy is required to make N2 molecules vibrate than is required to make I2 molecules vibrate. B) More energy is required to remove an electron from an I2 molecule than is required to remove an electron from a N2 molecule. C) Visible light does not produce transitions between electronic energy levels in the N2 molecule but does produce transitions in the I2 molecule.. D) The molecular mass of I2 is greater than the molecular mass of N2 .
The ideal gas law best describes the properties of which of the following gases at 0°C and 1 atm? 3.6 MC Questions
A) PH3 B) HBr C) SO2 D) N2
Which of the following techniques is most appropriate for the recovery of solid KNO3 from an aqueous solution of KNO3 ? 3.9 MC Questions
A) Paper chromatography B) Filtration C) Titration D) Electrolysis E) Evaporation to dryness
Beta-carotene is an organic compound with an orange color. The diagram above shows the ultraviolet spectrum of beta-carotene. Which of the following statements is true about the absorption bands in the spectrum? 3.11 MC Questions
A) The absorption band between 250 and 320nm is due to transitions in electronic energy levels, and the absorption band between 380 and 520nm is due to transitions in molecular vibrational levels. B) The absorption band between 250 and 320nm is due to transitions in molecular vibrational levels, and the absorption band between 380 and 520nm is due to transitions in molecular rotational levels. C) The two main absorption bands are associated with transitions in electronic energy levels. The band in the region corresponding to shorter wavelengths shows a lower absorbance than the band in the region corresponding to longer wavelengths. D) The two main absorption bands are associated with transitions in molecular vibrational levels. The band in the region corresponding to shorter wavelengths shows a lower absorbance than the band in the region corresponding to longer wavelengths.
The volume of a sample of air in a cylinder with a movable piston is 2.0 L at a pressure P1 , as shown in the diagram above. The volume is increased to 5.0 L as the temperature is held constant. The pressure of the air in the cylinder is now P2 . What effect do the volume and pressure changes have on the average kinetic energy of the molecules in the sample? 3.5 MC Questions
A) The average kinetic energy increases. B) The average kinetic energy decreases. C) The average kinetic energy stays the same. D) It cannot be determined how the kinetic energy is affected without knowing P1 and P2 .
A 1L sample of helium gas at 25°C and 1atm is combined with a 1L sample of neon gas at 25°C and 1atm. The temperature is kept constant. Which of the following statements about combining the gases is correct? 3.5 MC Questions
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.
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? 3.4 MC Questions
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
Which statement best helps to explain the observation that NH3 (l) boils at -28°C , whereas PH3 (l) boils at -126 °C ? 3.2
A) The dispersion forces in NH3 are weaker than the dispersion forces in PH3 . B) The dispersion forces in NH3 are stronger than the dipole-dipole forces in PH3 . C) NH3 has hydrogen bonding that is stronger than the dipole-dipole forces in PH3 . D) NH3 has hydrogen bonding that is weaker than the dipole-dipole forces in PH3 .
The diagrams opposite 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? 3.6 MC Questions
A) 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 Xe 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.
Diagram 1 above shows equimolar samples of two gases inside a container fitted with a removable barrier placed so that each gas occupies the same volume. The barrier is carefully removed as the temperature is held constant. Diagram 2 above shows the gases soon after the barrier is removed. Which statement describes the changes to the initial pressure of each gas and the final partial pressure of each gas in the mixture and also indicates the final total pressure? 3.4 MC Questions
A) The partial pressure of each gas in the mixture is double its initial pressure; the final total pressure is half the sum of the initial pressures of the two gases. B) The partial pressure of each gas in the mixture is double its initial pressure; the final total pressure is twice the sum of the initial pressures of the two gases. C) The partial pressure of each gas in the mixture is half its initial pressure; the final total pressure is half the sum of the initial pressures of the two gases. D) The partial pressure of each gas in the mixture is half its initial pressure; the final total pressure is the same as the sum of the initial pressures of the two gases.
Ar(g) deviates more from ideal behavior at extremely high pressures than Ne(g) does. Which of the following is one reason for this difference? 3.6 MC Questions
A) The particle volume of Ar is greater than that of Ne B) Ar atoms have more valence electrons than Ne atoms have, so Ar atoms have greater interparticle forces. C) The intermolecular forces between Ne atoms are greater than those between Ar atoms. D) Ar atoms are more attracted to the walls of the container than Ne atoms are.
The reaction between NO(g) and O2(g) to produce NO2(g) in a rigid reaction vessel is represented in the diagram above. The pressure inside the container is recorded using a pressure gauge. Which of the following statements correctly predicts the change in pressure as the reaction goes to completion at constant temperature, and provides the correct explanation? 3.4 MC Questions
A) The pressure will increase because the product molecules have a greater mass than either of the reactant molecules. B) The pressure will decrease because there are fewer molecules of product than of reactants. C) The pressure will decrease because the product molecules have a lower average speed than the reactant molecules. D) The pressure will not change because the total mass of the product molecules is the same as the total mass of the reactant molecules.
Which of the following is not shown in the model but best helps to explain why flask C must contain pentane? 3.1
A) The random motion of the particles within the liquids. B) The relative speeds of the vapor particles in each flask. C) The strength of the intermolecular forces between the particles in the liquids. D) The structural formula of the molecules of the liquid and vapor in each flask.
The diagrams above show the ultraviolet absorption spectra for two compounds. Diagram 1 is the absorption spectrum of pure acetone, a solvent used when preparing solutions for an experiment. Diagram 2 is the absorption spectrum of the solute for which the absorbance needs to be measured to determine its concentration. When the student reads the absorbance of the solution at 280nm, the result is too high. Which of the following is most likely responsible for the error in the measured absorbance? 3.13 MC Questions
A) The student added too little solute to the acetone before measuring its absorbance. B) The student rinsed the cuvette with the solution before filling the cuvette with the solution. C) The student forgot to calibrate the spectrophotometer first by using a cuvette containing only acetone. D) The wavelength setting was accidentally changed from 280nm to 300nm before the student made the measurement.
A rigid metal tank contains oxygen gas. Which of the following applies to the gas in the tank when additional oxygen is added at constant temperature? 3.5 MC Questions
A) The volume of the gas increases. B) The pressure of the gas decreases. C) The average speed of the gas molecules remains the same. D) The total number of gas molecules remains the same. E) The average distance between the gas molecules increases.
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.
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 student made the standard curve above. Which of the following most likely caused the error in the point the student plotted at 0.050 M Co2+ (aq) ?
A) There was distilled water in the cuvette when the student put the standard solution in it. B) There were a few drops of the 0.100 M Co2+ (aq) standard solution in the cuvette when the student put the 0.050 M standard solution in it. C) The student used a cuvette with a longer path length than the cuvette used for the other standard solutions. D) The student did not run a blank between the 0.050 M Co2+ (aq) solution and the one before it.
The diagram above shows a thin-layer chromatogram of a mixture of products from a chemical reaction. The separation was performed using 50% ethyl acetate in hexane as the solvent (mobile phase) and silica gel as the polar stationary phase. On the basis of the chromatogram and the information about solvents in the table above, which of the following would be the best way to decrease the distance that the products travel up the plate? 3.9 MC Questions
A) Use pentane instead of hexane in the solvent. B) Decrease the percentage of ethyl acetate in the solvent. C) Increase the percentage of ethyl acetate in the solvent. D) Add up to 5% methanol to the solvent.
Which of the following is the best piece of laboratory glassware for preparing 500.0 mL of an aqueous solution of a solid? 3.7 MC Questions
A) Volumetric Falsk B) Erlenmeyer flask C) Test tube D) Graduated beaker E) Graduated cylinder
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? 3.9 MC Questions
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.
Based on concepts of polarity and hydrogen bonding, which of the following sequences correctly lists the compounds above in the order of their increasing solubility in water? 3.7 FRQ
A) Z < Y < X B) Y < Z < X C) Y < X < Z D) X < Z < Y E) X < Y < Z
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 3.2
A) a covalent network solid B) a metallic solid C) a polymer D) an ionic solid E) a molecular solid
Of the following, the best explanation for the fact that most gases are easily compressed is that the molecules in a gas 3.3 MC Question
A) 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
The best explanation for the fact that diamond is extremely hard is that diamond crystals
A) are made up of atoms that are intrinsically hard because of their electronic structures B) consist of positive and negative ions that are strongly attracted to each other C) are giant molecules in which each atom forms strong covalent bonds with all of its neighboring atoms D) are formed under extreme conditions of temperature and pressure E) contain orbitals or bands of delocalized electrons that belong not to single atoms but to each crystal as a whole
A sample of an unknown gas from a cylinder is collected over water in the apparatus shown opposite. 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 3.4 MC Questions
A) 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
At standard temperature and pressure, a 0.50 mol sample of H2 gas and a separate 1.0 mol sample of O2 gas have the same 3.5 MC Questions
A) average molecular kinetic energy B) average molecular speed C) volume D) effusion rate E) density
At constant temperature, the behavior of a sample of a real gas more closely approximates that of an ideal gas as its volume is increased because the 3.6 MC Questions
A) collisions with the walls of the container become less frequent B) average molecular speed decreases C) molecules have expanded D) average distance between molecules becomes greater. E) average molecular kinetic energy decreases.
Which flask contains the sample with the greatest density? 3.4 MC Questions
A) flask A B) flask B C) flask C D) flask D E) flask E
Which flask contains the smallest number of moles of gas? 3.4 MC Questions
A) flask A B) flask B C) flask C D) flask D E) flask E
The average kinetic energy of the gas molecules is? 3.5 MC Questions
A) greatest in A B) greatest in B C) greatest in C D) the same in all three containers
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. Under the conditions given, consider containers 1, 2, and 4 only. The average speed of the gas particles is
A) greatest in container 1 B) greatest in container 2 C) greatest in container 4 D) the same in containers 1, 2, and 4
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... 3.6 MC Questions
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 π bonds, while the other gases contain only σ bonds
In solid methane, the forces between neighboring CH4 molecules are best characterized as 3.2
A) ionic bonds B) covalent bonds C) hydrogen bonds D) ion-dipole forces E) london (dispersion) forces
A sample of a hard, solid binary compound at room temperature did not conduct electricity as a pure solid but became highly conductive when dissolved in water. Which of the following types of interactions is most likely found between the particles in the substance? 3.2
A) ionic bonds B) metallic bonds C) covalent bonds D) hydrogen bonds O O
Which of the following is the strongest type of interaction that occurs between the atoms within the circled areas of the two molecules represented below? 3.1
A) polar covalent bond B) non-polar covalent bond C) hydrogen bond D) london dispersion force
When the actual gas volume is greater than the volume predicted by the ideal gas law, the explanation lies in the fact that the ideal gas law does NOT include a factor for molecular 3.6 MC Questions
A) volume B) mass C) velocity D) attractions E) shape
The figure above represents three sealed 1.0 L vessels, each containing a different inert gas at 298 K. The pressure of Ar in the first vessel is 2.0 atm. The ratio of the numbers of Ar, Ne, and He atoms in the vessels is 2 : 1 : 6, respectively. 3.4 MC Questions
After all the gases are combined in a previously evacuated 2.0 L vessel, what is the total pressure of the gases at 298 K? A) 3.0 atm B) 4.5 atm C) 9.0 atm D) 18 atm
The student measures the actual pressure of the CO2(g) in the container at 425K and observes that it is less than the pressure predicted by the ideal gas law. (**Last part of question asked in previous section.) 3.6 FRQ
Explain this observation.
The Lewis electron-dot diagrams for molecules of CH4 and CCl4 are shown opposite. CCl4(l) is placed in a previously evacuated container at 30°C, and some of the CCl4(l) evaporates. 3.3 FRQ
In the box below, draw a particulate diagram to show the species in the container after some of the CCl4(l) has evaporated.
The structures of a water molecule and a crystal of LiCl(s) are represented opposite. A student prepares a 1.0 M solution by dissolving 4.2 g of LiCl(s) in enough water to make 100 mL of solution. 3.8 & 3.10 FRQ
In the space provided below, show the interactions of the components of LiCl(aq) by making a drawing that represents the different particles present in the solution. Base the particles in your drawing on the particles shown in the representations above. Include only one formula unit of LiCl and no more than ten molecules of water. Your drawing must include the following details. • identity of ions (symbol and charge) • the arrangement and proper orientation of the particles in the solution
At 400K CH4(g) and CCl4(g)are gases. At this temperature, which compound, CH4(g) or CCl4(g), behaves more like an ideal gas? 3.6 FRQ
Justify your answer, including reasoning about both molecules.
M+ is an unknown metal cation with a +1 charge. A student dissolves the chloride of the unknown metal, MCl, in enough water to make 100.0 mL of solution. The student then mixes the solution with excess AgNO3 solution, causing AgCl to precipitate. The student collects the precipitate by filtration, dries it, and records the data shown below. (The molar mass ofAgCl is 143 g/mol.) 3.7 FRQ
Mass of unknown chloride MCl = 0.74 g Mass of filter paper = 0.80 g Mass of filter paper plus AgCl precipitate = 2.23 g Which of the following diagrams best represents the AgNO3 solution before the reaction occurs? Note: water molecules are represented by the symbol
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. 3.4 MC Questions
On the basis of the data provided above, the gas in container 3 could be A) CH4 B) O2 C) Ar D) CO2
This question refer to three gases in identical rigid containers under the conditions given in the table below. 3.4 MC Questions
The density of the gas, in g/L, is A) greatest in container A B) greatest in container B C) greatest in container C D) the same for all 3 containers
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 3.3×10−19 J 3.12 MC Questions
Which of the following is closest to the frequency of the light with photon energy of 3.3 × 10−19 J ? A 5.0 × 10−53 s−1 B 5.0 × 10−16 s−1 C 5.0 × 1014 s−1 D 5.0 × 1052 s−1 Using the wavelength information provided above, what is the color of the light? A) Red B) Orange C) Yellow D) Blue
A student was assigned the task of determining the molar mass of an unknown gas. The student measured the mass of a sealed 843 mL rigid flask that contained dry air. The student then flushed the flask with the unknown gas, resealed it, and measured the mass again. Both the air and the unknown gas were at 23.0°C and 750. torr. The data for the experiment are shown in the table below. 3.4 FRQ
a) Calculate the mass, in grams, of the dry air that was in the sealed flask. (The density of dry air is 1.18 g L−1 at 23.0°C and 750. torr.) 1 point is earned for the correct setup and calculation of mass. m = D x V = (1.18 g L−1)(0.843 L) = 0.995 g b) Calculate the mass, in grams, of the sealed flask itself (i.e., if it had no air in it). 1 point is earned for subtracting the answer in part a) from 157.70 g. 157.70 g − 0.995 g = 156.71 g c) Calculate the mass, in grams, of the unknown gas that was added to the sealed flask. 1 point is earned for subtracting the answer in part b) from 158.08 g. 158.08 g − 156.71 g = 1.37 g d) Using the information above, calculate the value of the molar mass of the unknown gas. e) After the experiment was completed, the instructor informed the student that the unknown gas was carbon dioxide (44.0 g mol−1) . Calculate the percent error in the value of the molar mass calculated in part d) f) For each of the following two possible occurrences, indicate whether it by itself could have been responsible for the error in the student's experimental result. You need not include any calculations with your answer. For each of the possible occurrences, justify your answer. Occurrence 1: The flask was incompletely flushed with CO2(g) , resulting in some dry air remaining in the flask. Occurrence 2: The temperature of the air was 23.0°C, but the temperature of the CO2(g) was lower than the reported 23.0°C. g) Describe the steps of a laboratory method that the student could use to verify that the volume of the rigid flask is 843 mL at 23.0°C. You need not include any calculations with your answer
Solid carbon and carbon dioxide gas at 1,160 K were placed in a rigid 2.00 L container, and the reaction represented above occurred. As the reaction proceeded, the total pressure in the container was monitored. When equilibrium was reached, there was still some C(s) remaining in the container. Results are recorded in the table opposite. 3.4 FRQ
a) Calculate the number of moles of CO2(g) initially placed in the container. (Assume that the volume of the solid carbon is negligible.) b) For the reaction mixture at equilibrium at 1,160 K, the partial pressure of the CO2(g) is 1.63 atm. Calculate the partial pressure of CO(g)
When heated, calcium carbonate decomposes according to the equation above. In a study of the decomposition of calcium carbonate, a student added a 50.0 g sample of powdered CaCO3(s) to a 1.00 L rigid container. The student sealed the container, pumped out all the gases, then heated the container in an oven at 1100 K. As the container was heated, the total pressure of the CO2(g) in the container was measured over time. The data are plotted in the graph opposite. The student repeated the experiment, but this time the student used a 100.0 g sample of powdered CaCO3(s). In this experiment, the final pressure in the container was 1.04 atm, which was the same final pressure as in the first experiment. 3.4 FRQ
a) Calculate the number of moles of CO2(g) present in the container after 20 minutes of heating. b) The student claimed that the final pressure in the container in each experiment became constant because all of the CaCO3(s) had decomposed. Based on the data in the experiments, do you agree with this claim? Explain.
When heated strongly, solid calcium carbonate decomposes to produce solid calcium oxide and carbon dioxide gas, as represented by the equation above. A 2.0mol sample of CaCO3(s) is placed in a rigid 100.L reaction vessel from which all the air has been evacuated. The vessel is heated to 898°C at which time the pressure of CO2(g) in the vessel is constant at 1.00atm, while some CaCO3(s) remains in the vessel. 3.4 FRQ
a) Calculate the number of moles of CO2(g) present in the vessel at equilibrium. b) The experiment was repeated, but this time starting with a 4.0mol sample of CaCO3(s). On the following graph, draw a curve showing how the pressure of CO2(g) would change over time as the vessel is heated to 898°C and equilibrium is established.
A student performs an experiment to determine the volume of hydrogen gas produced when a given mass of magnesium reacts with excess HCl(aq) , as represented by the net ionic equation above. The student begins with a 0.0360 g sample of pure magnesium and a solution of 2.0 M HCl(aq) 3.7 FRQ
a) Calculate the number of moles of magnesium in the 0.0360 g sample. b) Calculate the number of moles of HCl(aq) needed to react completely with the sample of magnesium. As the magnesium reacts, the hydrogen gas produced is collected by water displacement at 23.0°C. The pressure of the gas in the collection tube is measured to be 749 torr. c) Given that the equilibrium vapor pressure of water is 21 torr at 23.0°C, calculate the pressure that the H2(g) produced in the reaction would have if it were dry. d) Calculate the volume, in liters measured at the conditions in the laboratory, that the H2(g) produced in the reaction would have if it were dry.
A student is doing experiments with CO2(g). Originally, a sample of the gas is in a rigid container at 299K and 0.70atm. The student increases the temperature of the CO2(g) in the container to 425K. (**This question might be best left until after next section on deviations fron Ideal Gas.) 3.5 FRQ
a) Describe the effect of raising the temperature on the motion of the CO2(g) molecules. The response indicates that the average speed of the molecules increases as temperature increases b) Calculate the pressure of the CO2(g) in the container at 425K. The response shows a calculation similar to the following. P1 / T1 = P2 / T2 0.70 atm / 425 K = P2 / 425 K P2 = 0.99 atm c) In terms of kinetic molecular theory, briefly explain why the pressure of the CO2(g) in the container changes as it is heated to 425K d) The student measures the actual pressure of the CO2(g) in the container at 425K and observes that it is less than the pressure predicted by the ideal gas law. Explain this observation.
The structures for glucose, C6 H12O6 , and cyclohexane, C6 H12 , are shown opposite. 3.2 FRQ
a) Identify the type(s) of intermolecular attractive forces in i) pure glucose 1 point is earned for the correct answer. Hydrogen bonding OR dipole-dipole interactions OR van der Waals interactions (London dispersion forces may also be mentioned.) ii) pure cyclohexane 1 point is earned for London dispersion forces. b) Glucose is soluble in water but cyclohexane is not soluble in water. Explain.
After elemental analysis the empirical formula of a compound was determined to be CH2 Br . It was also found to have a vapor density of 6.00 g L−1 at 375 K and 0.983 atm. Using these data, determine the following. 3.4 FRQ
a) The molar mass of the compound b) The molecular formula of the compound
A student is given a sample of CuSO4(s) that contains a solid impurity that is soluble and colorless. The student wants to determine the amount of CuSO4 in the sample and decides to use a spectrophotometer. First, the student prepares a calibration graph by measuring the absorbances of CuSO4(aq) solutions of known concentrations. The graph is shown. 3.7 FRQ
a) The student dissolves the entire impure sample of CuSO4(s) in enough distilled water to make 100.mL of solution. Then the student measures the absorbance of the solution and observes that it is 0.30. Determine the concentration of CuSO4(aq) in the solution b) Calculate the number of moles of CuSO4 that were in the impure sample of CuSO4(s) In addition to the number of moles of CuSO4 calculated in part b), what other quantity must be measured in order to calculate the mass percentage of CuSO4 in the impure sample of CuSO4(s) ?
A student is given 50.0mL of a solution of Na2 CO3 of unknown concentration. To determine the concentration of the solution, the student mixes the solution with excess 1.0MCa(NO3 )2(aq), causing a precipitate to form. The balanced equation for the reaction is shown below. 3.8 & 3.10 FRQ
a) Write the net ionic equation for the reaction that occurs when the solutions of Na2 CO3 and Ca(NO3 )2 are mixed. b) The diagram below is incomplete. Draw in the species needed to accurately represent the major ionic species remaining in the solution after the reaction has been completed.
Answer the following questions by using principles of molecular structure and intermolecular forces. 3.1
a) pic b) pic c) The normal boiling point of Cl2 (l) (238 K) is higher than the normal boiling point of HCl(l) (188 K). Account for the difference in normal boiling points based on the types of intermolecular forces in the substances. You must discuss both of the substances in your answer.
