AP Chem Unit 3
If the solubility of BaF2 is equal to x, which of the following expressions is equal to the solubility product, Ksp, for BaF2? (A) x^2 (B) 2x^2 (C) 2x^3 (D) 4x^3
4x^3
Describe how H2O and KCl molecules would react in solution.
In solution the H+ atoms in H2O would orient themselves towards the negatively charged Cl- and the O2- atoms in H2O would orient themselves toward the positive K+.
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?
The average kinetic energy of the helium atoms and neon atoms do not change when the gases are combined.
Why does an increase in concentration increase the rate of reaction? (A) Collisions become more effective (B) The number of collisions increases. (C) The activation energy decreases. (D) The average kinetic energy increases. (E) When there are more molecules in the container, they all speed up.
The number of collisions increases.
Based on the 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?
X<Y<Z
Beaker X and beaker Y each contain 1.0 L of solution, as shown above. A student combines the solutions by pouring them into a larger, previously empty beaker Z and observes the formation of a white precipitate. Assuming that volumes are additive, which of the following sets of solutions could be represented by the diagram above?
2.0 M AgNO3 | 1.0 M MgCl2 | 0.50 M Mg(NO3)2 and AgCl(s)
What volume of a 0.100MHCl stock solution should be used to prepare 250.00mLof 0.0250MHCl?
62.5ml
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.
shown above best represents the strongest intermolecular force between two ammonia, NH3, molecules?
Diagram 2- hydrogen bonding between nitrogen and hydrogen atoms in different molecules.
Which of the following correctly indicates whether the solid represented by the particulate model shown above conducts electricity and explains why or why not?
It does not conduct electricity because its ions cannot move freely within the solid
Draw a diagram that best represents the speed of gas particles at a fixed temp. What was it drawn this way?
The gas particles at a fixed temperature will not all have the same speed. They will have variety of speed as described by the Maxwell-Boltzmann distribution.
The limiting reactant is the reactant (A) for which you have the lowest mass in grams (B) which has the lowest coefficient in the balanced equation (C) which has the lowest molar mass (D) which is left over after the reaction has gone to completion (E) none of the above
(E) none of the above
If the pressure of each gas is increased at constant temperature until condensation occurs, which gas will condense at the lowest pressure?
Butane
in which flask has the greatest average speed?
largest temperature, smallest pressure
A saturated solution... (A) contains as much solvent as it can hold (B) contains no double bonds (C) contains dissolved solute in equilibrium with undissolved solute (D) will rapidly precipitate if a seed crystal is added (E) cannot be attained
none of the above
Explain what happens at the molecular level as CO2 molecules absorb photons of the infrared radiation.
As CO2 absorbs the infrared radiation photons, the vibrations amongst the molecules will increase. This is because the bonds are bending and stretching and infrared radiation is associated with transitions in molecular vibration levels.
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?
KNO3
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.
How can you use paper chromatography to find the number of components in a sample?
Paper chromatography can be used to find the number of components in a sample because it Is able to separate small quantities of a mixture into its parts. This is done by using different solutions with various 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?
Paper chromatography using different solvents with a range of polarities as the mobile phase
Which of the following salts is insoluble in water? A) Na2S (B) K2CO3 (C) Pb(NO3)2 (D) NH4Cl (E) All of these are soluble in water.
E) All of these are soluble in water.
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? 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.
b. The pressure will decrease because there are fewer molecules of product than of reactants.
The survival of aquatic organisms depends on the small amount of O2 that dissolves in H2O. The diagrams above represent possible models to explain this phenomenon. Which diagram provides the better particle representation for the solubility of O2 in H2O, and why?
Diagram 2, because the polar H2O molecules can induce temporary dipoles on the electron clouds of O2 molecules.
What volume of .2 M HCl stock solution should be used to prepare 500 mL of .02 M HCl?
50 mL
How many grams of N2O5 gas are in a sample that has a volume of 2.00 Liters at 298 K and 100. kPa of pressure.
8.72
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?
He(g) will escape faster because the He(g) atoms are moving at a higher average speed than the Ne(g) atoms.
Which statement best helps to explain the observation that NH3(l) boils at -28 degrees C but PH3(I) boils at -126 degrees c?
c. NH3 has hydrogen bonding that is stronger than the dipole-dipole forces in PH3.
In an experiment on the photoelectric effect, a photon with a frequency of 7×1014s−1was absorbed by a sample. What is the approximate energy of this photon?
5×10−19J
The following questions refer to the 1 L flasks shown below. Which flask contains the smallest number of moles?
b. T= 50 CP= 0.5 atm
Based on their Lewis diagrams, which of the following pairs of liquids are most soluble in each other?
C2H5OH and H20 (both polar)
In the diagram above, which of the labeled arrows identifies hydrogen bonding in water?
D; O---H
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+ ions and the Cl− ions are weaker than those between the ions in MgS.
How many grams of CaCl2 (molar mass =111g/mol) are needed to prepare 100.mLof 0.100MCl−(aq) ions?
0.555 g
A 2 L container will hold about 4 g of which of the following gases at 0°C and 1 atm?
CO2
The ideal gas law best describes the properties of which of the following gases at 0 degrees C and 1 atm?
He
Which of the following gases deviates most from ideal behavior?
SO2
Which of the following is not a postulate of the kinetic molecular theory?
a. Gas particles have most of their mass concentrated in the nucleus of the atom.
in which flask has the smallest number of moles of gas
largest temperature, smallest pressure
What is the mass of a 6.267-mol sample of sodium hydroxide? (A) 0.50 g (B) 2.0 g (C) 4.0 g (D) 8.0 g (E) 16 g
250.7 g
In which of the following liquids do the intermolecular forces include dipole-dipole forces?
CH2F2(l)
What would be the best procedure to separate a mixture of NaCl and H2O?
Distillation
Which of the following behaves most like an ideal gas at the conditions indicated?
H2(g) molecules at 10-3 atm and 200oC
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.
In which of the following aqueous solutions would you expect AgCl to have the highest solubility? (A) pure water (B) 0.020 M BaCl2 (C) 0.015 NaCl (D) 0.020 AgNO3 (E) 0.020 KCl
pure water
How many mL of 10.0 M HCl are needed to prepare 500 mL of 2.00 M HCl?
100 mL
In an experiment on the photoelectric effect, a photon with a frequency of 9*10^11 s^-1 was absorbed by a sample. What is the approximate energy of this photon?
5.96*10^-22 J
Based on the data in the table above, which of the following liquid substances has the weakest intermolecular forces?
CH3OH(l)
in which flask has the highest density?
highest pressure temp ratio
Under which of the following conditions of temperature and pressure will H2 gas be expected to behave most like an ideal gas?
largest temperature, smallest pressure
A 360. mg sample of aspirin, C9H8O4, (molar mass 180. g), is dissolved in enough water to produce 200 mL of solution. What is the molarity of aspirin in a 50. L sample of this solution?
0.0100 M
How many moles of Na+ ions are in 100.mL of 0.100MNa3PO4(aq) ?
0.0300 mol (.1x.1 times 3)
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
2 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?
5 atm
A gaseous air‑fuel mixture in a sealed car engine cylinder has an initial volume of 360.mL at 1.0 atm. To prepare for ignition of the fuel, a piston moves within the cylinder, reducing the volume of the air‑fuel mixture to 40.mL at constant temperature. Assuming ideal behavior, what is the new pressure of the air‑fuel mixture?
About 9 atm, because the volume of the gas mixture decreased by a factor of 9.
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.
Which of the following gasses would have a smaller molar mass and why?
Gas Z would have a smaller molar mass. This is because the two gasses are at the same temperature so their kinetic energies are the same. However the curve for gas Z shows that it has a higher average speed than the molecules in gas X. Therefore Gas Z has a smaller molar mass.
A 14.0 gram sample of an unknown gas occupies 11.2 L at standard temperature and pressure. Which of the following could be the identity of the gas? I. N2 II. CO2 III. CO (A) I only (B) II only (C) I and III only (D) II and III only (E) I,II, and III
I and III only
Changes in which of the factors affect both rate and rate constant? I. temperature II. concentration
I only
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?
It depends on the relative molecular masses of X, Y, and Z.
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. What can explain this observation?
More moles of ions present in a given volume of 0.10 M Na2SO4 than in the same volume of 0.10 M NaCl.
The ideal gas law best describes the properties of which of the following gases at 0°C and 1 atm?
N2
Which of the following best helps explain why the pressure of a sample of CH4(g) (molar mass 16g/mol) is closer to the pressure predicted by the ideal gas law than a sample of NH3(g) (molar mass 17g/mol) ?
NH3 molecules are polar while CH4 molecules are not, and the greater attractions between NH3 molecules cause the molecules to collide with the walls of the container with less force.
Zn(s) is used to reduce other compounds in chemical reactions. If a chemist needs a substance that is more effective in its reducing ability, which of the following species would be the best choice? A) Na B) H+1 C) K+1 D) Cl-1
Na
Based on Coulomb's Law and the information in the table above, which of the following cations is most likely to have the weakest interaction with an adjacent water molecule in an aqueous solution?
Na+
In an aqueous solution of an ionic salt, the oxygen atom of water molecule is attracted to the...
Positive ion of the salt, due to oxygen's partial negative charge
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.
What occurs when photons of visible light are absorbed by molecules of dye?
The absorption of the photons in the visible range will cause the electrons in the dye molecules to transition between energy levels.
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.
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?
The carbon chains are longer in nonane than they are in 2,3,4-trifluoropentane.
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.
The student made the standard curve above. What most likely caused the error in the point the student plotted at 0.050 M Co2+?
There was distilled water in the cuvette when the student put the standard solution in it.
Which of the following pairs are inversely proportional to each other, assuming other conditions are kept constant? a. volume, pressure b. temperature, avg. kinetic energy c. avg. kinetic energy, pressure d. effusion rate, temperature.
a. volume, pressure
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
average distance between molecules becomes greater
Based on the data in the table below, which of the following liquid substances has the weakest IMFs?
c. CH3OH (you can tell from the data b/c it has the highest vapor pressure and vapor pressure is inversely proportional to IMF strength)
A reaction produces a gaseous mixture of carbon dioxide, carbon monoxide, and water vapor. After one reaction, the mixture was analyzed and found to contain 0.60 mol of carbon dioxide, 0.30 mol of carbon monoxide, and 0.10 mol of water vapor. If the total pressure of the mixture was 0.80 atm, what was the partial pressure of the carbon monoxide? a. 0.080 atm b. 0.34 atm c. 0.13 atm d. 0.24 atm
d. 0.24 atm
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
forces among Br2 molecules are stronger than those among Cl2 molecules
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?
the particle volume of Ar is greater than that of Ne
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?
the pressure of the gas
A compound is heated to produce a gas whose molecular weight is to be determined. The gas is collected by displacing water in a water-filled flask inverted in a trough of water. Which of the following is necessary to calculate the molecular weight of the gas, but does NOT need to be measured during the experiment?
vapor pressure of the water
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.
volume
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
average molecular kinetic energy
When water is added to a mixture of Na2O2(s) and S (s) , a redox reaction occurs, as represented by the equation below.
0 in na202 each atom gains one electron
In which of the following aqueous solutions would you expect AgCl to have the lowest solubility? (A) pure water (B) 0.020 M BaCl2 (C) 0.015 NaCl (D) 0.020 AgNO3 (E) 0.020 KCl
0.020 M BaCl2
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.
0.200M
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- in the resulting solution? (Assume that the volumes are additive.)
0.28 M
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?
1.0 m
The average kinetic energy of the helium atoms and neon atoms do not change when the gases are combined.
Gas Z has a smaller molar mass than gas X.
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?
Zn2+ > Ca2+ > Ba2+ because the smaller ions have a stronger coulombic attraction to water
A 1.15 mol sample of carbon monoxide gas has a temperature of 27°C and a pressure of 0.300 atm. If the temperature were lowered to 17°C, at constant volume, what would be the new pressure? a. 0.290 atm b. 0.519 atm c. 0.206 atm d. 0.338 atm
a. 0.290 atm
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? 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. He(g) will escape faster because the He(g) atoms are moving at a higher average speed than the Ne(g) atoms.
A gas will behave more like an ideal gas if it has an _____ and an ___________. a. Increased volume, increased temperature b. Increased temperature, increased average kinetic energy c. Increased average kinetic energy, increased pressure d. Increased effusion rate, increased pressure
a. Increased volume, increased temperature
PCl5(g) decomposes into PCl3(g) and Cl2(g) according to the equation above. A pure sample of PCl5(g) is placed in a rigid, evacuated 1.00L container. The initial pressure of the PCl5(g) is 1.00 atm. The temperature is held constant until the PCl5(g) reaches equilibrium with its decomposition products. The figures below show the initial and equilibrium conditions of the system. Which of the following is the most likely cause for the increase in pressure observed in the container as the reaction reaches equilibrium?
C) An increase in the number of molecules, which increases the frequency of collisions with the walls of the container
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.
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.
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?
average speed stays the same
The diagram above shows the distribution of speeds for a sample of N2(g) at 25°C. Which of the following graphs shows the distribution of speeds for a sample of O2(g) at 25°C (dashed line) ?
higher and longer (first diagram)
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
the pressure of the gas
A 0.20 mol sample of of MgCl2 and a .10 mol sample of KCl are dissolved in water and diluted to 500 mL. What is the concentration of Cl- in the solution?
1.0 M
How many grams of MgCl2 (molar mass 95.21 g/mol) are need to prepare 250 mL of .05 M MgCl2 solution.
1.19 g MgCl2
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) ?
3rd - low dashed, average solid
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.
Ne, HF, C2H6, CH4 Which of the substances listed above has the highest boiling point, and why? 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
B)HF, because its molecules form hydrogen bonds
Aqueous solutions of sodium sulfide and copper (II) chloride are mixed together. Which statement is correct? (A) Both NaCl and CuS precipitate from solution. (B) No reaction will occur. (C) CuS will precipitate from solution. (D) NaCl will precipitate from solution. (E) A gas is released.
CuS will precipitate from solution.
Explain how excess water left in a cuvette could skew the results of measured absorbance.
Excess water in the cuvette would cause the results of measured absorbance to be lower than expected because the water would dilute the sample solution.
A student places a piece of I2(s) in 50.0 mL of H2O(l), another piece of I2(s) of the same mass in 50.0 mL of C6H14(l), and shakes the mixtures. The results are shown above. What do the results indicate about the intermolecular interactions of the substances?
I2 and C6H14 have similar intermolecular interactions, and I2 and H2Odo not (similar can dissolve)
The electron cloud of HF is smaller than that of F2, however, HF has a much higher boiling point (293 K) than F2 (85 K) has. What 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
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?
Testing the electrical conductivity of an aqueous solution of the substance
Four different liquid compounds in flasks at 20°C 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?
The strength of the intermolecular forces between the particles in the liquids
Aluminum metal reacts with HCl to produce aluminum chloride and hydrogen gas. How many grams of aluminum metal must be added to an excess of HCl to produce 33.6 L of hydrogen gas, if the gas is at STP?
c. 27.0 g
A sample of Neon gas is sealed in a container. The volume of the container is doubled. If the pressure remains constant, what happens to the absolute temperature? a. It does not change. b. It is halved. c. It is doubled. d. It is squared.
c. It is doubled.
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
C3H8 + 4Cl2 <-> C3H4Cl4 + 4HCl A 6.0 mol sample of C3H8 and a 20. mol sample of Cl2 are placed in a previously evacuated vessel, where they react according to the equation above. After one of the reactants has been totally consumed, how many moles of HCl have been produced? A) 4.0 mol B) 8.0 mol C) 20. mol D) 24 mol
20. mol
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 x 10^-19 J
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?
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.
N2 molecules absorbs ultravoilet light but not visible light. I2 molecules absorb both visible and ultraviolet light. Which of the following statements explains the observations? 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 an 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
Visible light does not produce transitions between electronic energy levels in the N2 molecule but does produce transitions in the I2 molecule.
Which of the following particulate diagrams best shows the formation of water vapor from hydrogen gas and oxygen gas in a rigid container at 125 C?
c. (looks like some 3 big oo yields 6 water)
The graph below shoes the distribution for four different gases at the same temperature. What property of the gases can be correctly ranked using information from the graph, and why?
d. The molecular masses of the gases, because the gas molecules have the same average kinetic energy and mass and can be calculated using the equivalent KE = 1/2mv.
The graph to the right shows the distribution of molecular speeds for four different gases at the same temperature. What property of the different gases can be correctly ranked using the information from the graph and why? a. The densities of the gases, because as the density of a gas increases, the average speed of its molecule decreases. b. The pressures of the gases, because the pressure exerted by a gas depends on the average speed with which its molecules are moving. c. The volumes of the gases, because at a fixed temperature the volume of a gas can be calculated using the equation PV=nRT d. The molecular masses of the gases, because the gas molecules have the same kinetic energy and mass can be calculated using the equation KEavg=1/2mv2
d. The molecular masses of the gases, because the gas molecules have the same kinetic energy and mass can be calculated using the equation KEavg=1/2mv2
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
have stronger intermolecular attractions than the other three gases
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
iii only
A given mass of gas in a rigid container is heated from 100 °C to 300 °C. Which of the following best describes what will happen to the pressure of the gas? The pressure will... (A) decrease by a factor of three (B) increase by a factor of three (C) increase by a factor less than three (D) decrease by a factor greater than three (E) unable to be determined without information about volume
increase by a factor of three
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?
molecule attached to hydrogen
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
How many grams of NaCl (molarmass=58g/mol) are needed to prepare 100.mL of a 0.25M NaCl solution?
1.5 g
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 atm
A gas mixture at 0°C and 1.0atm contains 0.010mol of H2, 0.015mol of O2, and 0.025molof N2. Assuming ideal behavior, what is the partial pressure of hydrogen gas (H2) in the mixture?
About 0.20atm, because H2 comprises 20% of the total number of moles of gas.
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 gas C2H6 has a larger, more polarizable electron cloud than the gas CH4. How does the deviation of C2H6 from an ideal gas compare to that of CH4, explain?
The deviation from an idea, gas will be greater in C2H6. This is because it has a larger, more polarizable electron cloud that increases and strengthens its intermolecular forces. In an ideal gas the attraction between particles is negligible so C2H6 will have a larger deviation than CH4.
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.
Of the following, the best explanation for the fact that most gases are easily compressed is that the molecules in a gas
are relatively far apart
Given that the density of Hg at 0*C is about 14 g mL, which of the following is closest to the volume of one mole of Hg at this temperature?
14 mL
A flask with a pressure of 2000 mmHg contains 6 mol of helium with a partial pressure of 1500 mmHg. The remaining gas is hydrogen, what is the mass of hydrogen in the flask?
4.0 g
A 17.0 g sample of HF is dissolved in water to give 2.0 * 10^2 mL of solution. The concentration of the solution is: (A) 0.85 M (B) 0.17 M (C) 0.09 M (D) 4.2 M (E) 8.5 M
4.2 M
What is the relationship between absorbance and transmittance of light through a sample in a spectrophotometer? (A) An increase in transmittance usually results in an increase in absorbance. (B) A decrease in transmittance usually results in a decrease in absorbance. (C) A decrease in transmittance usually results in an increase in absorbance. (D) Transmittance and absorbance should remain equal.
A decrease in transmittance usually results in an increase in absorbance.
Which statement about the factors that affect reaction rates is false? (A) Decreasing the concentrations of the reacting particles decreases the chance of collision (B) A collision with poor orientation requires a higher activation energy than a collision with optimum orientation (C) Increasing the pressure in a gaseous reaction increases the chance of collision (D) A reaction occurs every time particles of the reactants collide (E) Increasing the temperature increases the reaction rate
A reaction occurs every time particles of the reactants collide
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 P4molecules in allotrope I.
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
Which of the following would deviate the most from an ideal gas at high temperatures and why? A) H2 B)F2 C)Ne D)SO2
D) SO2 SO2 would deviate the most from an ideal gas at high temperatures because of its large molecular volume. At higher temperatures, the volume consumed by the gas will be more significant and deviate greatly from an ideal gas with a volume that is negligible.
Thymine and adenine form a base pair in the DNA molecule. These two bases can form a connection between two strands of DNA via two hydrogen bonds. Which of the following diagrams shows the correct representation of the hydrogen bonding (denoted by dashed lines) between thymine and adenine base pairs? (In each diagram, thymine is shown at the left and adenine is shown at the right. The bases are attached to the backbone portion of the DNA strands.)
Diagram with O---H and H---N bonds
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.
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 particle-level diagram above represents the structure of solid KF. Although the molar mass of KCl is greater than that of KF, the density of KCl is actually less than that of KF. Which of the following representations of the structure of KCl best helps to explain this phenomenon?
The figure presents a particle diagram consisting of 5 small shaded circles, which represent positive ions and 4 large unshaded circles, which represent negative ions. The circles are arranged in 3 rows of 3, alternating between positive and negative ions. Rows 1 and 3 begin with a positive ion, and row 2 begins with a negative ion. There is quite a bit of space between the circles.
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 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...
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 diagrams to the right represent solutes present in two different dilute aqueous solutions before they were mixed. Water molecules are not shown. When the solutions were combined, a precipitation reaction took place. Which of the diagrams below is the best particle representation of the mixture after the precipitation reaction occurred?
d. (Na and NO3 are floading while AgCl connected at the bottom)
As the temperature of a reaction increased, the rate of the reaction increases because the... (A) reactant molecules collide less frequently (B) reactant molecules collide more frequently and with greater energy per collision (C) activation energy is lowered (D) reactant molecules collide less frequently AND with greater energy per collision (E) reactant molecules collide more frequently with less energy per collision
reactant molecules collide more frequently and with greater energy per collision
How many grams of NaCl are contained in 350 mL of a 0.334 M solution of sodium chloride? (A) 19.5 g (B) 6.83 g (C) 13.66 g (D) 116.9 g (E) none of these
6.83 g
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?
The average speed of the hydrogen molecules is the same as the average speed of the oxygen 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.
Which of the following best helps explain why the pressure of a sample of CH4(g) (molar mass 16g/mol) is closer to the pressure predicted by the ideal gas law than a sample of NH3(g)(molar mass 17g/mol) ?
NH3 molecules are polar while CH4 molecules are not, and the greater attractions between NH3 molecules cause the molecules to collide with the walls of the container with less force.
Which of the following is true of the triple point of a pure substance?
a. The vapor pressure of the solid phase always equals the vapor pressure of the liquid phase.
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. 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? 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.
c. The average kinetic energy stays the same.
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 280 nm, the result is too high. Which of the following is most likely responsible for the error in measured absorbance?
c. The student forgot to calibrate the spectrophotometer first by using a curvette containing acetone.
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?
The combined volume of the Ar atoms is too large to be negligible compared with the total volume of the container.
A sample of ammonia has a mass of 45.5 g. How many molecules are in this sample?
1.61 * 10^24 molecules
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 313283.
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?
5.6x10^14 s-1
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.
A 7.0 L container will hold about 12 g of which of the following gases at 0 °C and 1 atm? (A) F2 (B) Cl2 (C) Br2 (D) N2 (E) NO
F2
The distribution of speeds of H2(g) molecules at 273 K and 1 atm is shown in the diagram above. Which of the following best shows the speed distribution of He(g) atoms under the same conditions of temperature and pressure?
He will have larger bump as it has a larger molar mass
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+
Equal numbers of moles of He(g), Ar(g), and Ne(g) are placed in a glass vessel at room temperature. If the vessel has a pinhole-sized leak, which of the following will be true regarding the relative values of the partial pressures of the gases remaining in the vessel after some of the gas mixture has effused?
PHe < PNe < PAr
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.
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.
