ap chem semester 1 MCQs
which of the following is true after the product gases return to the original temperature and pressure, and why will the change occur?
A: the piston will be higher than its original position, because the cylinder will contain a greater number of gas molecules
[2H2O2 --> 2H2O + O2] the exothermic process represented above is best classified as a
D: chemical change because covalent bonds are broken and new covalent bonds are formed
which of the following lists the substances F2, HCl, and HF in order of increasing boiling point?
E: F2<HCl<HF
[0.1M HC2H3O2, 0.1M KI, 0.1M CH3OH] of the three solutions listed in the table above, which one, if any, has the greatest electrical conductivity and why?
B: 0.1M KI because KI completely disassociates in water to produce ions
what has the greatest mass of oxygen, Na2O, MgO, K2O, or CaO?
B: MgO
the mass spectrum of an average sample of a pure element is shown in the figure above. which of the following is the identity of the element?
B: Zr
[diagram with 4 CO molecules and 3 O2 molecules] which of the following best represents the contents of the box after the reaction has proceeded as completely as possible?
B: [4 CO2 molecules and 1 O2 molecule]
based on coulomb's law and the information in the table above, which of the following anions is most likely to have the strongest interactions with nearby water molecules in an aqueous solution?
C: S2-
compared to the equilibrium vapor pressure of CH3OH at 300K, the equilibrium vapor pressure of C2H5OH at 300K is
C: lower, because the London dispersion forces among C2H5OH molecules are greater than those among CH5OH molecules
on the basis of the data provided above, the gas in container 3 could be
A: CH4
which of the following equations best represents the species that react and the species that are produced when CaCO3 and HCl are combined?
B: 2H+ (aq) + CaCO3 (s) yields Ca2+ (aq) + H2O (l) + CO2 (g)
[shows 4 H2 molecules and 4 O2 molecules] a mixture of H2 and O2 is placed in a container as represented above. the H2 and O2 react to form H2O. which of the following best represents the container after the reaction has gone to completion?
B: [shows 2 O2 molecules and 4 H2O molecules]
[shows table] the density of the gas, in g/L is
B: greatest in container B
the diagram above [shows the positive end of water facing a molecule] represents a particle in aqueous solution. which of the following statements about the particle is correct?
B: the particle must be an anion because the positive end of each water molecule is pointed towards it
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?
B: the pressure will decrease because there are fewer molecules of product than reactants
[1 mol O2, 1 mol CO2, 2 moles CO2, 1 mole He] Which of the containers above has the least ideal behavior?
C: 2 moles CO2
the complete photoelectron spectra of neutral atoms of two unknown elements, X and Y, are shown above. which of the following can be inferred from the data?
C: element Y has a greater nuclear charge
[shows table comparing methane, ethane, and butane] the density of the gas, in g/L, is
C: greatest in container C
The graph above shows the speed distribution of molecules in a sample of gas at a certain temperature. Which of the following graphs shows the speed distribution of the same molecules at a lower temperature (as a dashed curve) ?
D: [graph w speed on x axis and number of molecules on y axis, dashed line peaks before solid line]
[shows table} the average kinetic energy of the gas molecules is
D: the same in all three containers
a sample of s solid labeled as NaCl may be impure. a student analyzes the sample and determines that it contains 75 percent chlorine by mass. pure NaCl contains 61 percent chlorine by mass. which of the following statements is consistent with the data?
D: the sample contains NaCl and LiCl
[shows structural formula of ethane and propanol] based on the structural formulas, which of the following identifies the compound that is more soluble in water and best helps to explain why?
D: propanol, because its molecules can form hydrogen bonds with water molecules but those of ethane cannot
the temperature of the CH3OH is increased from 300K to 400K to vaporize all the liquid, which increases the pressure in the vessel to 0.30 atm. the experiment is repeated under identical conditions but this time using half the mass of CH3OH that was used originally. what will be the pressure in the vessel at 400K?
A: 0.15atm
a sealed flask contains 1 molecule of hydrogen for every 3 molecules of helium at 20 °C. if the total pressure is 400 kPa, the partial pressure of the hydrogen is...
A: 100kPa
which of the following represents the ground state electron configuration for the Mn3+ ion? (atomic number Mn=25)
A: 1s2 2s2 2p6 3s2 3p6 3d4
if a pure sample of an oxide contains 40% sulfur and 60% oxygen by mass, then the empirical formula of the oxide is
A: SO3
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 to explain why boron nitride is so hard?
B: boron nitride is a network solid of atoms connected by covalent bonds with fixed bond angles
when 4.0 L of He(g), 6.0 L of N2(g), and 10. L of Ar(g), all at 0oC and 1.0 atm, are pumped into an evacuated 8.0 L rigid container, the final pressure in the container at 0oC is
C: 2.5 atm
under which of the following conditions of temperature and pressure will H2 gas be expected to behave most like an ideal gas?
C: 500K and 0.10 atm
[Li3N +2H2 yields LiNH3 + 2LiH] which of the following happens to H atoms in the forward reaction?
C: H atoms are both oxidized and reduced
a student titrates 10.0mL samples of 1.0 M solutions of each of the haloacetic acids with a standard solution of NaOH. which of the following statements correctly predicted the volume of needed to reach the equivalence point?
C: all of the acids will need the same volume of NaOH to reach equivalence point
which of the following helps to describe the solid represented in the digram above [shows big - and small + in a lattice]?
C: it is a brittle, water-soluble electrolyte that is a poor thermal and electrical conductor as a solid
at room temperature, I2 (s) is a molecular solid. which of the following provides a characteristic of I2 (s) with a correct explanation?
C: it is not a good conductor of electricity because its valence electrons are localized in bonding and nonbonding pairs
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?
C: the average kinetic energy stays the same
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?
C: the two main absorption bands are associated with transmission 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
which of the following is the molecular formula of the unknown compound?
D: C4H8O2
a student obtains a mixture of the liquids hexane and octane, which are miscible in all proportions. which of the following techniques would be best for separating the components of the mixture and why?
D: distillation, because the liquids would boil at different temperatures owing to the difference in strength of their intermolecular forces
three substances were studied in the laboratory, and the data in the table above were collected. based on the data. which of the following shows the type of bonding in each substance?
D: substance X: network covalent; substance Y: metallic; substance Z: ionic
Which of the following is NOT an assumption of the kinetic molecular theory for a gas?
D: the average velocity of the gas particles doubles when the absolute temperature doubles
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?
D: the combined volume of the Ar atoms is too large to be negligible compared with the total volume of the container
[diagram shows 3 H2 molecules and 2N2 molecules] which of the following diagrams would represent the results if the reaction shown below were to proceed as far as possible?
E: [2 NH3 molecules and 2 N2 molecules]
at 298K 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 Br molecules are stronger than those among Cl2 molecules
Under the conditions given, consider containers 1, 2, and 4 only. The average speed of the gas particles is
A: greatest in container 1
[the dimerization of NO2, an exothermic process is represented by 2NO2 yields N2O4] which of the following experimental techniques will allow the most accurate determination of the concentration of NO2 at equilibrium?
A: spectrophotometry
if 3.8 g of Cu(PO4)2 was recovered from step 1, what was the approximate Cu2+ in the original solution? (the molar mass of Cu(PO4)2 is 381 g/mol)
B: 0.3 M
based on the periodic trends and the data in the table above, which of the following are the most probably values of the atomic radius of the first ionization energy of potassium, respectively?
B: 242pm, 419 kJ/mol
[Li3N +2H2 yields LiNH3 + 2LiH] when 70 g of Li3N (molar mass 35 g/mol) reacts with excess H2, 8 g of LiH is produced. the percent yield is closest to
B: 25%
[At 27oC, five identical rigid 2.0 L vessels are filled with N2(g) and sealed. Four of the five vessels also contain a 0.050 mol sample of NaHCO3(s), NaBr(s), Cu(s), or I2(s), as shown in the diagram above. The volume taken up by the solids is negligible, and the initial pressure of N2(g) in each vessel is 720 mm Hg. All five vessels are heated to 127oC and allowed to reach a constant pressure.] At 127oC, the pressure in vessel 1 is found to be higher than that in vessel 2. Which of the following reactions best accounts for the observation?
C: 2 NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(g)
the compound CCl4 is nonflammable and was once commonly used in fire extinguishers. on the basis of periodic properties which of the following compounds can most likely be used as a fire-resistant chemical
C: CBr4
a 20 mL sample of 0.5 M HC2H3O2 is titrated with 0.5 M NaOH. which of the following best represents the species that react and the species produced in the reaction?
C: HC2H3O2 + OH- yields C2H3O2- + H2O
to determine the number of moles of Cu in the sample of the mixture, the students measured the absorbance of known concentration of Cu(NO3)2 using a spectrophotometer. a cuvette filled with some of the solution produced from the sample of the mixture was also tested. the data recorded by one student are shown in the table above. on the basis of the data provided, which of the following is a possible error that the student made?
C: the student labeled the cuvettes incorrectly, reversing the labels on two of the solutions of known concentration
[1 mol O2, 1 mol CO2, 2 moles CO2, 1 mole He] The diagram above shows containers of identical volume and temperature, but containing the different gases and molarities shown. Which of the containers has the fastest moving particles?
D: 1 mole He
[CO2 + 2LiOH yields Li2CO3 + H2O] **exhales 880g CO2 what mass of LiOH is needed to react completely with all of the CO2 produced by an astronaut in one day?
D: 960 g
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?
D: testing the electrical conductivity of an aqueous solution of the substance
which of the following correctly compares periodic properties of two elements and provides an accurate explanation for that difference?
D: the atomic radius of Cl is smaller than that of S because Cl has a larger nuclear charge than S does
which of the following best helps to explain why Na is more reactive than Mg is?
D: the first ionization energy of Na is less than that of Mg
the students determined that the reaction produced 0.010 mol of Cu(NO3)2. based on the measurement, what was the percent of Cu by madd in the original 2.00 sample of the mixture?
B: 32%
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. 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?
B: 4.5 atm
the ionization energies of an unknown element, X, are listed in the table above. which of the following is the most likely empirical formula of a compound formed from element X and phosphorus, P?
C: X3P2
[2MnO4- + 5H2O2 yields 6H+ + 2Mn2- + 5O2 + 8H2O] which of the following particle views best represents the mixture when the titration is halfway to the equivalence point?
C: [shows 5 peroxide molecules and 2 Mn ions]
[Use the table below for the next three questions. The table 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
C: have stronger intermolecular attractions than the other three gases
another sample of eggshell reacts completely with 4.0 mL of an HCl solution of unknown concentration. if the reaction produced 0.095 atm of gas, the concentration of the HCl solution was at least
D: 1.0M
when a 3.22 g sample of an unknown hydrate of sodium sulfate, Na2SO4 xH2O is heated, H2O (molar mass 18 g) is driven off. the mass of the anhydrous Na2SO4 (molar mass 142 g) that remains is 1.42 g. the value of x in the hydrate is
D: 10
[CH3OH(g) → CO(g) + 2 H2(g)] The reaction represented above goes to completion. The reaction takes place in a rigid, insulated vessel that is initially at 600 K. A sample of CH3OH(g) is placed in a previously evacuated vessel with a pressure of P1 at 600 K. What is the final pressure in the vessel after the reaction is complete and the contents of the vessel are returned to 600 K?
D: 3P1
equal volumes of solutions in two different vessels are represented above. if the solutioh represented in vessel 1 is KCl then the solution represented in vessel 2 could be an aqueous solution of
D: CaCl2 with twice the molarity as the solution in vessel 2
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?
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
Hydrogen gas is collected over water at 24 °C. The total pressure of the sample is 755 millimeters of mercury. At 24 °C, the vapor pressure of water is 22 millimeters of mercury. What is the partial pressure of the hydrogen gas?
B: 733mmHg
the first five ionization energies of an unknown element are listed in the table above. which of the following statements correctly identifies the element and cites the evidence supporting the identification?
B: Al because the large difference between the third and forth ionization energies
the photoelectron spectra for H and He are represented above. which of the following statements best accounts for the fact that the peak on the He spectrum is farther to the left and higher than the peak on the H spectrum?
B: He has a greater nuclear charge than H and an additional electron in the same energy level
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 3.3x10^-19 J. using the wavelength information above, what is the color of the light?
B: orange
the survival of all 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 and H2O, and why?
C: diagram 2, because the polar H2O molecules can induce temporary dipoles on the electron clouds of O2 molecules
which of the following particle diagrams best represents the products when four molecules of H2O2 decompose into water and oxygen gas at room temperature?
D: [shows 4 water molecules and 2 oxygen molecules]
which of the following best describes the change that takes place immediately after the CH3OH (l) is introduced into the previously evacuated vessel?
D: a physical change takes place because intermolecular attractions are overcome
[ClO2- + HCOOH yields HClO2 + HCOO] what are the relative strengths of the acids and bases in the reaction represented by the equation above?
D: acid strength: HClO2>HCOOH base strength: ClO2-
based on the structures shown above, which of the following statements identifies the compound with the higher boiling point and provides the best explanation for the higher boiling point?
D: compound 2, because it forms hydrogen bonds, whereas compound 1 does not
which of the following is true about the reaction?
D: it is a redox reaction, because Cu(s) is oxidized and the nitrogen atom in NO3- is reduced
the photoelectron spectra above show the energy required to remove the 1s electron from a nitrogen atom and from an oxygen atom. which of the following statements best accounts for the peak in the upper spectrum being to the right of the peak in the lower spectrum?
D: nitrogen atoms have a smaller nuclear charge than oxygen atoms
based on the table above [shows the structural formula and molar mass of butanol, pentane, and propanoic acid], which of the compounds has the highest boiling point, and why?
D: propanoic acid, because it can form intermolecular hydrogen bonds
