Unit 3 Test Review AP Chemistry
If the volume of a container is 1/3 of the size of the original container that has a pressure of 3 atm, what is the new pressure?
The new pressure is 9atm.
At what set of conditions of temperature and pressure, will a gas behave most as a real gas? A. 1100 K and 1 atm B. 1100 K and 100 atm C. 250 K and 1 atm D. 250 K and 100 atm
D. 250 K and 100 atm
The diagram above 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?
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.
Which of the diagrams above best represents the interactions that are responsible for the relatively large solubility of KCl crystals in water, and why?
Diagram 1, because strong ion-dipole interactions between KCl and water help to dissociate the solute.
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
If the pressure of each gas is increased at constant temperature until condensation occurs, which gas will condense at the lowest pressure?
C. Butane
Four different liquid compounds in flasks at are represented above. The table below identifies the compounds. Flask C shows the most particles in the vapor phase. Which of the following is not shown in the model but best helps to explain why flask C must contain pentane?
C. The strength of the intermolecular forces between the particles in the liquids
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?
C2H6 molecules have a larger, more polarizable electron cloud than CH4 molecules do.
Equal numbers of moles of CO2(g), N2(g), and NH3(g) are placed in a sealed vessel at room temperature. If the vessel has a pinhole-size leak, which of the following will be true after some of the gas mixture has effused? I. The mole fraction of CO2 in the sample will increase. II. The N2 will effuse the fastest since it is the lightest. III. All gases will effuse at the same rate since the temperature is held constant.
I. The mole fraction of CO2 in the sample will increase.
The diagram above 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?
It does not show how the temporary fluctuating dipoles of the molecular electron clouds result in a net force of attraction between the molecules.
Describe the orientation water around ions in CaCl2. Include the number of each ion you would need to draw so one formula unit of CaCl2 is correctly represented.
The Ca+ would have the negative O atoms attached and the Cl- will have the positive H atoms attached from H2O. There would be one Ca ion and two Cl ions.
(c) What volume of 0.20MNaCl(aq) contains 10.0g of NaCl (molar mass 58g/mol)?
The volume would be 860mL.
How many mL of 10.0 M HCl are needed to prepare 500. mL of 2.00 M HCl ?
100 mL
The volume of a gas collected when the temperature is 11.0°C and the pressure is 710 mm Hg measures 14.8 mL. What is the calculated volume of the gas at 20.0°C and 740 mm Hg?
14.7 mL
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?
5.6×10^14 s−1
What volume of a 0.100M HCl stock solution should be used to prepare 250.00mL of 0.0250M HCl?
62.5mL
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
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
The best explanation for the fact that diamond is extremely hard is that diamond crystals
C. are giant molecules in which each atom forms strong covalent bonds with all of its neighboring atoms
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?
The absorption of infrared radiation leads to an increase in molecular vibrational level associated with the stretching of the carbonyl.
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?
The particle is a positive ion, and the interactions are ion-dipole attractions.
during the course of the experiment, which of the following happens to the NO3- ions
d. they remain dissolved in the filtrate solution
Look at the two structural formulas and determine which one will have the lowest boiling point. Compound on the left or right. Explain. (C5H12)
the compound on the right because it has less surface area than the one on the left
What are two different ways to separate liquid mixtures?
two ways to separate liquid mixtures would be through chromatography and distillation
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?
4×10^−19 J
in .40 mol of H2 and .15 mol of O2 were to react as completely as possible to produce H2O what mass of reactant would remain
A. .20 g of H2
The boiling points of the elements helium, neon, argon, krypton, and xenon increase in that order. Which of the following statements accounts for this increase?
A. The London (dispersion) forces increase.
Based on the data in the table above, which of the following correctly predicts the relative strength of the attraction of Zn2+, Ca2+, and Ba2+ ions to water molecules in a solution, from strongest to weakest, and provides the correct reason?
A. Zn2+ > Ca2+ > Ba2+ because the smaller ions have a stronger coulombic attraction to water
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?
About 12atm , because the volume of the gas mixture decreased by a factor of 12.
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?
Allotrope II , because it has covalent bonds between the phosphorous atoms that are stronger than the dispersion forces between the P4 molecules in allotrope I .
Which of the following is the balanced net ionic equation for the reaction between Li(s) and water?
B
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?
Carbon atoms in diamond have four covalent bonds, whereas graphite is made of layers that are held together by relatively weak dispersion forces.
a .20 mol of sample of MgCl2 (s) and a .10 mol sample of KCL(s) are dissolved in water and diluted to 500mL what is the concentration of Cl-1 in the solution?
D. 1.0 M
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?
Diagram 2, because the particles have a variety of different speeds.
How would you describe a network solid?
They are solids bonded together by strong covalent bonds. They usually will have a high melting point.
in which of the following compounds does sulfer have an oxidation state of +4
b. h2so3
A 500.mL aqueous solution of Na3PO4 (molarmass=164g/mol) was prepared using 82 gof the solute. What is the molarity of Na3PO4 in the resulting solution?
1.0M
How many grams of NaCl (molarmass=58g/mol) are needed to prepare 100.mL of a 0.25M NaCl solution?
1.5g
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?
5×10^−19 J
Would C2H2 dissolve in water (H2O) or hexane (C6H14)? Explain.
C2H2 would dissolve into the hexane because both C2H2 are nonpolar while water is polar, causing the C2H2 to not want to dissolve into water.
Which of the following best explains what happens as photons of visible light are absorbed by dye molecules?
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.
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?
Diagram 1 represents NaCl; it has a lower melting point than MgS because the coulombic attractions between its singly charged Na+Na+ ions and the Cl− ions are weaker than those between the ions in MgS.
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?
The peak of the curve would be higher because more light would be absorbed.
What will happen to a flexible container filled with gas if the temperature is decrease?
The pressure of the gas would decrease because temperature and pressure are directly proportional
(b) Let P and V represent the pressure and volume of the Xe(g) in the container in diagram 3. If a piston is used to reduce the volume of the gas to V2 at a constant temperature, what is the new pressure in the container in terms of the original pressure, P ?
The pressure will be double the original pressure.
beaker x and y each contain 1.o L of solution, shown above. a student combines the solutions by pouring them into larger previously empty beaker z and observes the formation of a white precipitant. assuming the volumes are additive , whitch of the following sets of solutions could be represented by the diagram above?
d.
Why do we have solids, liquids and gases?
intermolecular forces and density
Which of the solids is a crystalline solid and which is a amorphous solid? ( A / B )
A is crystalline and B is amorphous
A sample of a compound that contains only he elements C, H, and N is completely burned in O2 to produce 44.0 g of CO2, 45.0 g of H2O, and some NO2. a possible empirical formula of the compound is
B. CH5N
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?
CO2 is a nonpolar molecule that has London dispersion intermolecular forces that are weaker than the dipole-dipole and London dispersion forces between the polar NH3 molecules.
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?
Crystalline NaBr contains no freely moving electrons to conduct electricity, but molten NaBr is composed of freely moving Na+ and Br− ions, which allows it to be a good conductor of electricity.
A 0.10 M aqueous solution of sodium sulfate, Na2SO4 , is a better conductor of electricity than a 0.10 M aqueous solution of sodium chloride, NaCl. Which of the following best explains this observation?
D. More moles of ions are present in a given volume of 0.10M Na2SO4 than in the same volume of 0.10 M NaCl.
Which particle diagram shown above best represents the strongest intermolecular force between two ethanol, C2H6O, molecules?
Diagram 2, because it shows the formation of a hydrogen bond between an H atom bonded to an O atom with an O atom from another molecule.
The diagram above shows the distribution of speeds for a sample of O2(g). Which of the following graphs shows the distribution of speeds for the same sample at a higher temperature (dashed line) ?
Diagram C
If the molarity of magnesium nitrate is 0.25 M, what is the concentration of the magnesium ion and the nitrate ion?
Mg: .25M & NO3: .50M
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?
SO2 , because it has the largest molecular volume.
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?
Solvent C
(b) Briefly explain how the presence of charged ions in ionic solids such as NaCl(s) helps to explain why NaCl(s) is soluble in water.
The anions and cations are attracted to the polar water molecule.
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?
The atoms in the CO2 molecules increase their vibration as the bonds between the atoms bend and stretch.
(c) Describe what happens to the average speed of the Xe atoms in the container in diagram 3 as the original volume V is reduced to V2 at a constant temperature. Explain.
The average speed will remain the same because the temperature is constant.
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?
2.3atm , because the pressure P increases by the proportion 313/283 .
The ionic compounds and are represented by the diagrams above. Which statement correctly identifies diagram 1 and identifies the compound with the lower melting point, explaining why?
B. Diagram 1 represents ; it has a lower melting point than because the coulombic attractions between its singly charged ions and the ions are weaker than those between the ions in .
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?
Boron nitride is a network solid of atoms connected by covalent bonds with fixed bond angles.
Nonane and 2,3,4-trifluoropentane have almost identical molar masses, but nonane has a significantly higher boiling point. Which of the following statements best helps explain this observation?
C. The carbon chains are longer in nonane than they are in 2,3,4-trifluoropentane.
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?
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.
Methanol, CH3OH, dissolves completely in water to form a solution that does not conduct electricity. Which of the following diagrams best shows the major type of attractive force that exists between the particles in the solution?
Diagram C
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?
Distillation
Is a strong electrolyte in aqueous solution
E. HBr(g)
In solid methane, the forces between neighboring CH4 molecules are best characterized as
E. London (dispersion) forces
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
E. a molecular solid
The two gas samples represented in the graph above are at the same temperature. Which of the following statements about the gases is correct?
Gas Z has a smaller molar mass than gas X .
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?
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.
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?
Mg2+ , because it has the largest charge-to-size ratio
Which statement best helps to explain the observation that NH3(l) boils at −28°C, whereas PH3(l) boils at −126°C?
NH3 has hydrogen bonding that is stronger than the dipole-dipole forces in PH3
Which of the following methods is most appropriate to use to determine the number of different-colored components in a sample of black ink?
Paper chromatography using different solvents with a range of polarities as the mobile phase
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?
The increase in conductivity indicates that the unknown is an ionic solid that dissociates into ions when it dissolves in water.
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?
The measured absorbance of the FeSCN2+ solution will be higher than the actual absorbance.
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?
The measured absorbance would be too low, because the distilled water left in the cuvette would slightly dilute the solution.
If the volume of a container is 1/2 of the size of the original container that has a temperature of 300 K, what is the new temperature when pressure remains constant?
The new temperature would be 600K because when the volume is decreased by half, the temperature would increase by doubling in heat.
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?
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.
