Herbig Semester Exam Review
A 2 L container will hold about 4 g of which of the following gases at 0°C and 1 atm?
CO2
Which of the following lists Mg, P, and Cl in order of increasing atomic radius?
Cl < P < Mg
HCl(aq)+H2O(l)→H3O+(aq)+Cl−(aq) For the dissolution of HCl in water represented above, which of the following pairs includes the Brønsted-Lowry bases?
H2O and Cl- (aq)
The diagram above shows molecules of Br2 and I2 drawn to the same scale. Which of the following is the best explanation for the difference in the boiling points of liquid Br2 and I2, which are 59 C and 184 C, respectively?
I2 molecules have electron clouds that are more polarizable than those of Br2 molecules, thus London dispersion forces are stronger in liquid I2.
The complete photoelectron spectrum for an element is shown above. Which of the following observations would provide evidence that the spectrum is consistent with the atomic model of the element?
In its compounds, the element tends to form ions with a charge of +1+1.
Which of the following best explains why more energy is required for the process occurring at 110 K than for the process occurring at 90 K ?
Intermolecular attractions are completely overcome during vaporization
Which of the following molecules contains polar covalent bonds but is a nonpolar molecule?
NH3
Has molecules with a pyramidal shape
NH3 (g)
Which of the following molecules has an angular (bent) geometry that is commonly represented as a resonance hybrid of two or more electron-dot structures?
O3
Which of the following numerical expressions gives the number of particles in 2.0g of Ne?
(2.0 g/20.18 g/mol)(6.0×1023particles/mol)
The enthalpy change for the reaction 2Al(s)+Fe2O3(s)→2Fe(s)+Al2O3(s) is −860kJ/mol. Based on the standard enthalpies of formation ΔH∘f provided in the table, what is the approximate ΔH∘f for Fe2O3(s) ?
-820 kJ/mol
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?
0.033 M
Which of the following represents a pair of isotopes?
1. 7 | 13 II. 7 | 14
Mg(s)+2HCl(aq)→MgCl2(aq)+H2(g) The chemical equation shown above represents the reaction between Mg(s) and HCl(aq). When 12.15g of Mg(s) is added to 500.0mL of 4.0MHCl(aq), 95kJ of heat is released. The experiment is repeated with 24.30g of Mg(s) and 500.0mL of 4.0MHCl(aq). Which of the following gives the correct value for the amount of heat released by the reaction?
190 kJ
Of the following electron configurations of neutral atoms, which represents an atom in an excited state?
1s2 2s2 2p5 3s2
Which of the following ground-state electron configurations represents the atom that has the lowest first-ionization energy?
1s2 2s2 2p6 3s1
Which of the following is the electron configuration of an excited atom that is likely to emit a quantum of energy?
1s2 2s2 2p6 3s1 3p1
The complete photoelectron spectrum of an element is given above. Which of the following electron configurations is consistent with the spectrum?
1s2 2s2 2p6 3s2 3p3
Which of the following represents the ground state electron configuration for the Mn3+ ion? (Atomic number Mn = 25)
1s2 2s2 2p6 3s2 3p6 3d4
Which of the following best represents the ground-state electron configuration for an atom of selenium?
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p4
Al(s)→Al3+(aq)+3e− Zn2+(aq)+2e−→Zn(s) The half-reactions for the oxidation-reduction reaction between Al(s) and Zn2+(aq) are represented above. Based on the half-reactions, what is the coefficient for Al(s) if the equation for the oxidation-reduction reaction is balanced with the smallest whole-number coefficients?
2
Which of the following is the balanced net-ionic equation for the reaction between Li(s) and water?
2 Li(s) + 2 H2O(l) → 2 Li+(aq) + 2 OH−(aq) + H2(g)
For an experiment, 50.0g of H2O was added to a coffee-cup calorimeter, as shown in the diagram above. The initial temperature of the H2O was 22.0°C, and it absorbed 300.J of heat from an object that was carefully placed inside the calorimeter. Assuming no heat is transferred to the surroundings, which of the following was the approximate temperature of the H2O after thermal equilibrium was reached? Assume that the specific heat capacity of H2O is 4.2J/(g⋅K).
23.4 C
Which of the following is the balanced net ionic equation for an oxidation-reduction reaction between Ag+(aq) and Ni(s) based on the half-reactions represented above?
2Ag+(aq)+Ni(s)→2Ag(s)+Ni2+(aq)
How much energy is required to melt 64 g of methane at 90 K? (The molar mass of methane is 16 g/mol and the delta H fus is 0.94 kJ/mol .)
3.8 kJ
A student uses visible spectrophotometry to determine the concentration of CoCl2(aq)CoCl2(aq) in a sample solution. First the student prepares a set of CoCl2(aq)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 510nm510nm and constructs a standard curve. Finally, the student determines the absorbance of the sample of unknown concentration. A wavelength of 510nm510nm corresponds to an approximate frequency of 6×1014s−16×1014s−1. What is the approximate energy of one photon of this light?
4 x 10^-19 J
An equation representing the dissociation of O2(g) and a table of bond enthalpies are shown above. Based on the information, which of the following is the enthalpy of dissociation for O2(g) ?
495 kJ/mol
The diagram above represents the photoelectric effect for a metal. When the metal surface is exposed to light with increasing frequency and energy of photons, electrons first begin to be ejected from the metal when the energy of the photons is 3.3×10−19J3.3×10−19J. Which of the following is closest to the frequency of the light with photon energy of 3.3×10−19J3.3×10−19J?
5.0 x 10^14 s^-1
A sample of CaCO3 (molar mass 100. g) was reported as being 30. percent Ca. Assuming no calcium was present in any impurities, the percent of CaCO3 in the sample is
75%
Which of the following Lewis diagrams best represents the bonding in the N2O molecule, considering formal charges?
:N:::N-O:::
A student mixes 20.0g of white KCl crystals with distilled water in a beaker. After the mixture was stirred, no crystals are visible and the solution is clear. After several days, all of the water evaporates and white crystals are found in the beaker. Which of following pieces of experimental evidence would best help the student to confirm that a new compound had not been made and that only a physical change occurred?
After the water has evaporated, the white crystals in the beaker have a mass of 20.0g20.0g.
The ionization energies for element X are listed in the table above. On the basis of the data, element X is most likely to be
Al
For a classroom demonstration, a chemistry teacher puts samples of two different pure solid powders in a beaker. The teacher places the beaker on a small wooden board with a wet surface, then stirs the contents of the beaker. After a short time the students observe that the bottom of the beaker is frozen to the wood surface. The teacher asks the students to make a claim about the observation and to justify their claims. Which of the following is the best claim and justification based on the students' observation?
An endothermic chemical change occurred because the temperature of the beaker and the water on the board decreased as heat was absorbed by the reaction.
If equal masses of the following compounds undergo complete combustion, which will yield the greatest mass of CO2?
Benzene, C6H6
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
The table above shows the structural formulas and molar masses for three different compounds. Which of the following is a list of the compounds in order of increasing boiling points? (compounds are acetone, 1-propanol, butane)
Butane < acetone < 1-propanol
Which of the molecules represented below contains carbon with sp2 hybridization?
C2H2Cl2
Which of the following molecules is nonpolar but has polar covalent bonds?
CCl4
Based on the information in the table above, which liquid, CS2(l) or CCl4(l), has the higher equilibrium vapor pressure at 25°C, and why? (the table has the molar mass of CS2 as 76 g/mol and bp at 46.5 C, while CCl4 has a molar mas of 154 g/mol and bp at 76.7 C)
CCl4 (l), because it has stronger London dispersion forces
In which of the following liquids do the intermolecular forces include dipole-dipole forces?
CH2F2 (l)
(A) CH3CH2CH2CH3 (B) CH3CH2CH2OH (C) CH3COCH3 (D) CH3COOH (E) CH3CH2CH2NH2 Which is isomeric with CH3CH2CHO
CH3COCH3
Pi (π) bonding occurs in each of the following species EXCEPT
CH4
On the basis of the information above, which of the following arranges the binary compounds in order of increasing bond polarity?
CH4 < SiCl4 < SF4
A sample of a compound that contains only the 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
CH5N
Which of the following is a nonpolar molecule that contains polar bonds?
CO2
The photoelectron spectra of the 1s electrons of two isoelectronic species, Ca2+ and Ar, are shown above. Which of the following correctly identifies the species associated with peak X and provides a valid justification?
Ca2+, because its nucleus has two more protons than the nucleus of Ar has
To make Au stronger and harder, it is often alloyed with other metals, such as Cu and Ag. Consider two alloys, one of Au and Cu and one of Au and Ag, each with the same mole fraction of Au. If the Au/Cu alloy is harder than the Au/Ag alloy, then which of the following is the best explanation based on the information in the table above?
Cu atoms are smaller than Ag atoms, thus they interfere more with the displacement of atoms in the alloy.
The London (dispersion) forces are weakest for which of the following gases under the same conditions of temperature and pressure
H2
(A) CO2 (B) H2O (C) CH4 (D) C2H4 (E) PH3 Which is the molecule with the largest dipole moment
H2O
The diagram above shows two resonance structures for a molecule of C6H6. The phenomenon shown in the diagram best supports which of the following claims about the bonding in C6H6 ?
In the C6H6C6H6 molecule, all the bonds between the carbon atoms have the same length.
Two pure elements react to form a compound. One element is an alkali metal, X, and the other element is a halogen, Z. Which of the following is the most valid scientific claim that can be made about the compound?
It contains ionic bonds.
The lattice energy of a salt is related to the energy required to separate the ions. For which of the following pairs of ions is the energy that is required to separate the ions largest? (Assume that the distance between the ions in each pair is equal to the sum of the ionic radii.)
Mg2+(g) and O2−(g)
1s2 2s2 2p6 3s2 3p3 Atoms of an element, X, have the electronic configuration shown above. The compound most likely formed with magnesium, Mg, is _________.
Mg3X2
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?
Microwave photons cause the molecules to increase their rotational energy states, whereas infrared photons cause the molecules to increase their vibrational energy states.
A student obtains a sample of a pure solid compound. In addition to Avogadro's number, which of the following must the student know in order to determine how many molecules are in the sample?
Molar mass of the compound, mass of the sample
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?
More moles of ions are present in a given volume of 0.10 M Na2SO4 than in the same volume of 0.10 M NaCl
Which of the following elements has the largest first ionization energy?
N
(A) BeCl2 (B) SO2 (C) N2 (D) O2 (E) F2 Which is the molecule in which the intramolecular forces are strongest
N2
(A) Li2 (B) B2 (C) N2 (D) O2 (E) F2 Which one contains 1 sigma (σ) and 2 pi (π) bonds
N2
(A) Li2 (B) B2 (C) N2 (D) O2 (E) F2 Which one has the largest bond-dissociation energy
N2
(A) H2O (B) NH3 (C) BH3 (D) CH4 (E) SiH4 Which has a trigonal-pyramidal molecular geometry
NH3
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.
The effective nuclear charge experienced by the outermost electron of Na is different than the effective nuclear charge experienced by the outermost electron of Ne. This difference best accounts for which of the following?
Na has a lower first ionization energy than Ne.
Based on the data in the tables above, which of the following statements provides the best prediction for the boiling point of NaCl ?
NaCl will have a lower boiling point than NaF because the coulombic attractions are weaker in NaCl than in NaF .
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.
NaOH (s)
The photoelectron spectra above show the energy required to remove a 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?
Nitrogen atoms have a smaller nuclear charge than oxygen atoms.
Assume that the bond enthalpies of the oxygenhydrogen bonds in H2O are not significantly different from those in H2O2 . Based on the value of ΔH° of the reaction, which of the following could be the bond enthalpies (in kJ/mol) for the bonds broken and formed in the reaction?
O-O in H2O2: 150 O=O in O2: 500 O-H: 500
(A) Li2 (B) B2 (C) N2 (D) O2 (E) F2 Which one has a bond order of 2
O2
Which of the following has a zero dipole moment?
PF5
(A) CO2 (B) H2O (C) CH4 (D) C2H4 (E) PH3 Which is the molecule that has trigonal pyramidal geometry
PH3
Equal volumes of 0.2M solutions of lead(II) nitrate and potassium bromide are combined to form lead(II) bromide as a yellow precipitate. Which of the following is the correct net ionic equation for the reaction?
Pb2+(aq)+2Br−(aq) → PbBr2(s)
A sample containing atoms of C and F was analyzed using x-ray photoelectron spectroscopy. The portion of the spectrum showing the 1s peaks for atoms of the two elements is shown above. Which of the following correctly identifies the 1s peak for the F atoms and provides an appropriate explanation?
Peak X, because F has a greater nuclear charge than C has.
Which of the following statements, if true, would support the claim that the NO3− ion, represented above, has three resonance structures?
The NO3− ion is not a polar species.
The elements C and Se have the same electronegativity value, 2.55. Which of the following claims about the compound that forms from C and Se is most likely to be true?
The carbon-to-selenium bond is nonpolar covalent.
The energy required to dissociate an ionic solid into gaseous ions (lattice energy) for the compounds NaF and MgF2 is shown in the table above. On the basis of Coulomb's law, which of the following best helps to explain the large difference between the lattice energies of NaF and MgF2 ?
The charge of the Mg cation is larger than that of the Na cation
The photoelectron spectrum for the element nitrogen is represented above. Which of the following best explains how the spectrum is consistent with the electron shell model of the atom?
The electrons in the 2p2p sublevel have the smallest binding energy.
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?
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.
CO(g) + 2 H2(g) ⇄ CH3OH(g) ΔH < 0 The synthesis of CH3OH(g) from CO(g) and H2(g) is represented by the equation above. The value of Kc for the reaction at 483 K is 14.5.
The energy absorbed as the bonds in the reactants are broken is less than the energy released as the bonds in the product are formed.
A sample of CHCl3(s) was exposed to a constant source of heat for a period of time. The graph above shows the change in the temperature of the sample as heat is added. Which of the following best describes what occurs at the particle level that makes segment D longer than segment B?
The enthalpy of vaporization is greater than the enthalpy of fusion, because separating molecules completely from the liquid to form a gas requires more energy than separating molecules from their bound crystalline state to a liquid state.
A student is given two 10g samples, each a mixture of only NaCl(s) and KCl(s) but in different proportions. Which of the following pieces of information could be used to determine which mixture has the higher proportion of KCl(s) ?
The mass of Cl in each mixture
A 5.0g sample of MgCl2 may contain measurable amounts of other compounds as impurities. Which of the following quantities is (are) needed to determine that the sample is pure MgCl2 ?
The mass of Mg and the mass of Cl in the sample
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
CH3OH(g) ---> CO(g) + 2H2(g) delta H = +91 kJ/mol rxn The reaction represented above goes essentially to completion. The reaction takes place in a rigid, insulated vessel that is initially at 600 K Which of the following statements about the bonds in the reactants and products is most accurate?
The sum of the bond enthalpies of the bonds in the reactant is greater than the sum of the bond enthalpies of the bonds in the products.
A student had two dilute, colorless solutions, HCl(aq) and NaOH(aq), which were at the same temperature. The student combined the solutions, and the reaction represented above occurred. Which of the following results would be evidence that a chemical reaction took place?
The temperature of the reaction mixture increases
HCl(aq)+NaOH(aq)→NaCl(aq)+H2O(l) A student had two dilute, colorless solutions, HCl(aq) and NaOH(aq), which were at the same temperature. The student combined the solutions, and the reaction represented above occurred. Which of the following results would be evidence that a chemical reaction took place?
The temperature of the reaction mixture increases.
NaOH(aq) + HCl(aq) → H2O(l) + NaCl(aq) A student is trying to determine the heat of reaction for the acid-base neutralization reaction represented above. The student uses 0.50 M NaOH and 0.50 M HCl solutions. Which of the following situations, by itself, would most likely result in the LEAST error in the calculated value of the heat of reaction?
The thermometer was incorrectly calibrated and read 0.5 Celsius degree too high during the procedure.
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?
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.
The table above shows the first ionization energy and atomic radius of several elements. Which of the following best helps to explain the deviation of the first ionization energy of oxygen from the overall trend?
There is repulsion between paired electrons in oxygen's 2p orbitals.
The BF3 molecule is nonpolar, whereas the NF3 molecule is polar. Which of the following statements accounts for the difference in polarity of the two molecules?
Unlike BF3, NF3 has a nonplanar geometry due to an unshared pair of electrons on the N atom.
Which of the following best helps explain why the electronegativity of Cl is less than that of F?
When Cl and F form bonds with other atoms, the Cl bonding electrons are more shielded from the positive Cl nucleus than the F bonding electrons are shielded from the positive F nucleus.
The graphs above show Maxwell-Boltzmann distributions for one-mole samples of Ar(g). Graph 1 shows the distribution of particle energies at 300K and graph 2 shows the distribution of particle energies at 600K. A student predicts that if the samples are combined in an insulated container and thermal equilibrium is attained, then the most probable particle energy will be between the most probable energy shown in graph 1 and the most probable energy shown in graph 2. Which of the following is the best justification for the student's claim?
When the samples are combined, the gas particles will collide with one another, with the net effect being that energy will be transferred from the more energetic particles to the less energetic particles until a new distribution of energies is achieved at a temperature between 300K and 600K.
A student has samples of two pure compounds, XClO3 and ZClO3, which contain unknown alkali metals X and Z. The student measures the mass of each sample and then strongly heats the samples to drive off all the oxygen, leaving solid residues of XCl and ZCl. The student measures the mass of the solid residue from each sample. Which of the following questions can be answered from the results of the experiment?
Which has the greater molar mass, XX or ZZ?
A student has two samples of NaCl, each one from a different source. Assume that the only potential contaminant in each sample is KCl. The student runs an experiment to determine the percent by mass of chlorine in each sample. From the results of this experiment alone, which of the following questions is most likely to be answered?
Which sample has the higher purity?
A certain crystalline substance that has a low melting point does not conduct electricity in solution or when melted. This substance is likely to be
a molecular solid
The best explanation for the fact that diamond is extremely hard is that diamond crystals
are giant molecules in which each atom forms strong covalent bonds with all of its neighboring atoms
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
Which of the following properties generally decreases across the periodic table from sodium to chlorine?
atomic radius
According to the VSEPR model, the progressive decrease in the bond angles in the series of molecules CH4, NH3, and H2O is best accounted for by the
increasing number of unshared pairs of electrons
Which of the following represents an electron configuration that corresponds to the valence electrons of an element for which there is an especially large jump between the second and third ionization energies? (Note: n represents a principal quantum number equal to or greater than 2.)
ns2
Which of the following substances is a strong electrolyte when dissolved in water?
sodium nitrate
H - C ≡ C - H What is the hybridization of the carbon atoms in a molecule of ethyne, represented above?
sp
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?
the London dispersion forces increase
2F2(g)+2NaOH(aq)→OF2(g)+2NaF(aq)+H2O(l) A 2mol sample of F2(g) reacts with excess NaOH(aq) according to the equation above. If the reaction is repeated with excess NaOH(aq) but with 1 mol of F2(g), which of the following is correct?
the amount of OF2 (g) produced is halved
The figure above shows two closed containers. Each contains the same volume of acetone in equilibrium with its vapor at the same temperature. The vapor pressure of the acetone is
the same in both containers because the temperature is the same
The geometry of the SO3 molecule is best described as
trigonal planar
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
The mass percent of carbon in pure glucose, C6H12O6, is 40.0 percent. A chemist analyzes an impure sample of glucose and determines that the mass percent of carbon is 38.2 percent. Which of the following impurities could account for the low mass percent of carbon in the sample?
water, H2O
Which of the following graphs correctly shows the relationship between potential energy and internuclear separation for two hydrogen atoms?
(the one with the weird curve)
Reaction 1: N2O4(g)→2NO2(g) ΔH1=+57.9kJ Reaction 2: 2NO(g)+O2(g)→2NO2(g) ΔH2=−113.1kJ Based on the information for two different reactions given above, which of the following gives the quantities needed to calculate the enthalpy change for the reaction represented by the overall equation below? 2NO(g)+O2(g)→N2O4(g)
(−ΔH1)+ΔH2
Shown above are the equation representing the decomposition of H2O2(l) and a table of bond enthalpies. On the basis of the information, which of the following is the enthalpy of decomposition of 2 mol of H2O2(l) ?
-203 kJ
2H2S(g)+3O2(g)→2H2O(l)+2SO2(g) ΔH°=−1120kJ/molrxn Based on the reaction represented by the chemical equation shown above, what is the amount of heat released when 4.00mol of H2S(g) reacts with 9.00mol of O2(g)?
-2240 kJ
A 2.00mol sample of C2H5OH undergoes the phase transition illustrated in the diagram above. The molar enthalpy of vaporization, ΔHvap, of C2H5OH is +38.6kJ/mol. Which of the following best identifies the change in enthalpy in the phase transition shown in the diagram?
-77.2 kJ
5 Fe2+ + MnO4- + 8 H+ ⇄ 5 Fe3+ + Mn2+ + 4 H2O In a titration experiment based on the equation above, 25.0 milliliters of an acidified Fe2+ solution requires 14.0 milliliters of standard 0.050-molar MnO4- solution to reach the equivalence point. The concentration of Fe2+ in the original solution is
0.14 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).
0.20 M
Fe (s) + 2HCl (aq) --> FeCl2 (aq) +H2 (g) When a student adds 30.0 mL of 1.00 M HCl to 0.56 g of powdered Fe, a reaction occurs according to the equation above. When the reaction is complete at 273 K and 1.0 atm, which of the following is true?
0.22 L of H2 has been produced
When a 3.22 g sample of an unknown hydrate of sodium sulfate, Na2SO4 ⋅ H2O(s), is heated, H2O (molar mass 18 g) is driven off. The mass of the anhydrous Na2SO4(s) (molar mass 142 g) that remains is 1.42 g. The value of x in the hydrate is
10.
. . . C10H12O4S(s) + . . . O2(g) → . . . CO2(g) + . . . SO2(g) + . . . H2O(g) When the equation above is balanced and all coefficients are reduced to their lowest whole-number terms, the coefficient for O2(g) is
12
The diagram above represents the melting of H2O(s). A 2.00mole sample of H2O(s) at 0°C melted, producing H2O(l) at 0°C. Based on the diagram, which of the following best describes the amount of heat required for this process and the changes that took place at the molecular level?
12.0 kJ of heat was absorbed to overcome some of the hydrogen bonding forces holding the water molecules in fixed positions in the crystalline structure
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?
14 mL
Which of the following is the ground-state electron configuration of the F- ion?
1s2 2s2 2p6
C3H8(g) + 4 Cl2(g) → C3H4Cl4(g) + 4 HCl(g) A 6.0 mol sample of C3H8(g) and a 20. mol sample of Cl2(g) 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(g) have been produced?
20. mol
Based on periodic trends and the data in the table above, which of the following are the most probable values of the atomic radius and the first ionization energy for potassium, respectively?
242 pm, 419 kJ/mol
Which of the following molecules contains exactly three sigma (σ) bonds and two pi (π) bonds?
C2H2
A student was studying physical and chemical changes. The student carried out some procedures in the laboratory and recorded observations. For one of the procedures, the student concluded that a physical change took place, but not a chemical change. Which of the following could have been the results of the procedure?
A cube of metal was changed into a flat sheet of metal.
(A) A network solid with covalent bonding (B) A molecular solid with zero dipole moment (C) A molecular solid with hydrogen bonding (D) An ionic solid (E) A metallic solid Solid ethyl alcohol, C2H5OH is which of the above
A molecular solid with hydrogen bonding
To gravimetrically analyze the silver content of a piece of jewelry made from an alloy of Ag and Cu, a student dissolves a small preweighed sample in HNO3(aq). Ag+(aq)and Cu2+(aq) ions form in the solution. Which of the following should be the next step in the analytical process?
Adding a solution containing an anion that forms an insoluble salt with only one of the metal ions
Which of the following correctly identifies which has the higher first-ionization energy, Cl or Ar, and supplies the best justification?
Ar, because of its higher effective nuclear charge
The first five ionization energies of a second-period element are listed in the table above. Which of the following correctly identifies the element and best explains the data in the table?
B, because it has three valence electrons
(A) H2O (B) NH3 (C) BH3 (D) CH4 (E) SiH4 Has a central atom with less than an octet of electrons
BH3
(A) H2O (B) NH3 (C) BH3 (D) CH4 (E) SiH4 Which is predicted to have the largest bond angle
BH3
(A) Cs (B) Ag (C) Pb (D) Br (E) Se Which one has the highest electronegativity?
Br
(A) 2 C6H6(l) + 15 O2(g) → 12 CO2(g) + 6 H2O(l) (B) C2H3O2-(aq) + H3O+(aq) → HC2H3O2(aq) + H2O(l) (C) 4 H+(aq) + 4 Co2+(aq) + O2(g) + 24 NH3(aq) → 4 Co(NH3)63+(aq) + 2 H2O(l) (D) CaCO3(s) → CaO(s) + CO2(g) (E) 2 H2O2(l) → O2(g) + 2 H2O(l) Which is the reaction between a Brønsted-Lowry acid and a Brønsted-Lowry base
C2H3O2-(aq) + H3O+(aq) → HC2H3O2(aq) + H2O(l)
(A) CO2 (B) H2O (C) CH4 (D) C2H4 (E) PH3 Which is the molecule with only one double bond
C2H4
Complete combustion of a sample of a hydrocarbon in excess oxygen produces equimolar quantities of carbon dioxide and water. Which of the following could be the molecular formula of the compound?
C4H8
Which of the following molecules has the shortest bond length?
Cl2
Which of the following species is NOT planar?
ClF3
The elements in which of the following have most nearly the same atomic radius?
Cr, Mn, Fe, Co
In which of the following compounds is the mass ratio of chromium to oxygen closest to 1.62 to 1.00?
CrO2
What is the empirical formula of an oxide of chromium that is 48 percent oxygen by mass?
CrO3
(A) Cs (B) Ag (C) Pb (D) Br (E) Se Which one has the largest atomic radius?
Cs
(A) Cs (B) Ag (C) Pb (D) Br (E) Se Which one has the lowest first-ionization energy?
Cs
The figure above shows that in solid hydrogen fluoride there are two different distances between H atoms and F atoms. Which of the following best accounts for the two different distances?
Difference in strength between covalent bonds and intermolecular attractions
Which of the following best helps to account for the fact that the F- ion is smaller than the O2- ion?
F- has a larger nuclear charge than O2- has.
Which of the following lists the substances F2, HCl, and HF in order of increasing boiling point?
F2 < HCl < HF
Which of the following arranges the molecules N2, O2, and F2 in order of their bond enthalpies, from least to greatest?
F2 < O2 < N2
Which of the following is the net ionic equation for the reaction between aqueous sodium fluoride and hydrochloric acid?
F−(aq)+H+(aq)→HF(aq)F−(aq)+H+(aq)→HF(aq)
Consider atoms of the following elements. Assume that the atoms are in the ground state. The atom that contains only one electron in the highest occupied energy sublevel is __________.
Ga
(A) H2O (B) NH3 (C) BH3 (D) CH4 (E) SiH4 Has two lone pairs of electrons
H2O
Of the following molecules, which has the largest dipole moment?
HF
At room temperature I2(s) is a molecular solid. Which of the following provides a characteristic of I2(s) with a correct explanation?
It is not a good conductor of electricity because its valence electrons are localized in bonding and nonbonding pairs
A student has a 1g sample of each of the following compounds: NaCl, KBr, and KCl. Which of the following lists the samples in order of increasing number of moles in the sample?
KBr<KCl<NaCl
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 HFHF has both weak dispersion force attractions and hydrogen bonding interactions between its molecules.
In solid methane, the forces between neighboring CH4 molecules are best characterized as
London dispersion forces
The enthalpy of vaporization of water is 40.7 kJ/mol. Which of the following best explains why the enthalpy of vaporization of methane is less than that of water?
Methane does not exhibit hydrogen bonding, but water does
NH3(aq) + HCl(aq) ⇄ NH4+(aq) + Cl-(aq) The Brønsted-Lowry bases in the reaction represented above are
NH3(aq) and Cl-(aq)
Which of the following compounds contains both ionic and covalent bonds?
NH4Cl
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?
Na
Of the following single bonds, which is the LEAST polar?
O-F
The diagram above represents the photoelectric effect for a metal. When the metal surface is exposed to light with increasing frequency and energy of photons, electrons first begin to be ejected from the metal when the energy of the photons is 3.3×10−19J3.3×10−19J. Using the wavelength information provided above, what is the color of the light?
Orange
The diagram above represents the absorption spectrum for a pure molecular substance. Which of the following correctly indicates the type of transition observed for the substance in each of the regions of the absorption spectrum?
Region X: Electronic transition, Region Y: Molecular vibration, Region Z: Molecular rotation
Consider atoms of the following elements. Assume that the atoms are in the ground state. The atom that contains exactly two unpaired electrons is __________.
S
(A) BeCl2 (B) SO2 (C) N2 (D) O2 (E) F2 Which is a polar molecule
SO2
(A) BeCl2 (B) SO2 (C) N2 (D) O2 (E) F2 Which one is best represented by two or more resonance forms
SO2
For which of the following molecules are resonance structures necessary to describe the bonding satisfactorily?
SO2
The potential energy of a system of two atoms as a function of their internuclear distance is shown in the diagram above. Which of the following is true regarding the forces between the atoms when their internuclear distance is x?
The attractive and repulsive forces are balanced, so the atoms will maintain an average internuclear distance x.
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
Which of the following scientific claims about the bond in the molecular compound HF is most likely to be true?
The bond is highly polar.
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
For element X represented above, which of the following is the most likely explanation for the large difference between the second and third ionization energies?
The electron removed during the third ionization is, on average, much closer to the nucleus than the first two electrons removed were.
C6H12O6+6O2→6CO2+6H2O The reaction between C6H12O6 and O2 is represented by the balanced equation above. In an experiment, 0.30mol of CO2 was produced from the reaction of 0.05mol of C6H12O6 with excess O2. The reaction was repeated at the same temperature and in the same container, but this time 0.60mol of CO2 was produced. Which of the following must be true?
The initial amount of C6H12O6C6H12O6 in the container must have been 0.10mol0.10mol.
A student was asked to formulate a hypothesis about what would happen if 100.mL of 0.1MNaOH(aq) at 25°C was combined with 100.mL of 0.1MMgCl2(aq) at 25°C. Which of the following hypotheses indicates that the student thought a chemical change would occur?
The resulting solution would contain a precipitate
A student was asked to formulate a hypothesis about what would happen if 100.mL of 0.1 M NaOH(aq) at 25°C was combined with 100.mL of 0.1 M MgCl2(aq) at 25°C. Which of the following hypotheses indicates that the student thought a chemical change would occur?
The resulting solution would contain a precipitate.
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
Which of the following best helps to explain why the electron affinity of Br has a greater magnitude than that of I?
There is a greater attraction between an added electron and the nucleus in BrBr than in II.
MgCl2(aq)+2NaOH(aq)→2NaCl(aq)+Mg(OH)2(s) A 100mL sample of 0.1MMgCl2(aq) and a 100mL sample of 0.2MNaOH(aq) were combined, and Mg(OH)2(s) precipitated, as shown by the equation above. If the experiment is repeated using solutions of the same molarity, which of the following changes in volume will double the amount of Mg(OH)2(s) produced?
Using twice the volume of MgCl2(aq) and twice the volume of NaOH(aq)
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?
Visible light does not produce transitions between electronic energy levels in the N2 molecule but does produce transitions in the I2 molecule.
The potential energy as a function of internuclear distance for three diatomic molecules, X2, Y2, and Z2, is shown in the graph above. Based on the data in the graph, which of the following correctly identifies the diatomic molecules, X2, Y2, and Z2?
X2: H2 Y2: N2 Z2: O2
Based on the ionization energies of element X given in the table above, which of the following is most likely the empirical formula of an oxide of element X?
X2O3
Reaction 1: CaC2(s) + 2 H2O(l) → C2H2(g) + Ca(OH)2(s) Reaction 2: NaOCl(aq) + 2 HCl(aq) → Cl2(g) + NaCl(aq) + H2O(l) Reaction 3: C2H2(g) + Cl2(g) → C2H2Cl2(g) When Reaction 3 occurs, does the hybridization of the carbon atoms change?
Yes; it changes from sp to sp2.
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? (radius, ion: 74, Zn2+; 100, Ca2+; 135, Ba2+)
Zn2+ > Ca2+ > Ba2+ because the smaller ions have a stronger coulombic attraction to water
Lewis electron-dot diagrams for CO2 and SO2 are given above. The molecular geometry and polarity of the two substances are
different because S has a greater number of electron domains (regions of electron density) surrounding it than C has
A particle-level diagram of a metallic element is shown above. Typically, metals are both malleable and ductile. The best explanation for these properties is that the electrons involved in bonding among metal atoms are
equally shared and form nondirectional bonds
At 298 K and 1 atm, bromine is a liquid with a high vapor pressure, whereas chlorine is a gas. This provides evidence that, under these conditions, the
forces among Br2 molecules are greater than those among Cl2 molecules
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?
ionic bonds
A molecular solid coexists with its liquid phase at its melting point. The solid-liquid mixture is heated, but the temperature does not change while the solid is melting. The best explanation for this phenomenon is that the heat absorbed by the mixture
is used in overcoming the intermolecular attractions in the solid
The oxidation of carbon monoxide can be represented by the chemical equation 2 CO(g)+O2(g)→2 CO2(g). The table above provides the average bond enthalpies for different bond types. Based on the information in the table, which of the following mathematical expressions is correct for the estimated enthalpy change for the reaction?
ΔHrxn=[2(1072kJmol)+(498kJmol)] − 4(799kJmol)
Based on the information in the table above, which of the following expressions gives the approximate ΔH° for the reaction represented by the following balanced chemical equation? Fe2O3(s)+3CO(g)→2Fe(s)+3CO2(g)
ΔH°rxn=[2(0kJ/mol)+3(−394kJ/mol)]−[(−826kJ/mol)+3(−111kJ/mol)]
