Chem Exam
Which of the following ions is most likely to form an insoluble sulfate?
Ca2+
Which of the following substances has bonds with the greatest ionic character?
CaCl2
For the dissolution of HCl in water represented above, which of the following pairs includes the Brønsted-Lowry bases?
H2O(l) and Cl- (aq)
The electron-dot structure for which of the following molecules would have two unshared pairs of electrons on the central atom?
H2S
Which of the following represents a pair of isotopes? Atomic Number | Mass Number
I. 7 | 13 II. 7 | 14
The mass spectrum of a sample of a pure element is shown above. Based on the data, the peak at 26amu represents an isotope of which of the following elements?
Mg with 14 neutrons
Which pair of ions would not be expected to form a precipitate when dilute solutions of each are mixed?
Mg+2, SO4-2
In the reaction represented above, the number of MnO4- ions that react must be equal to which of the following?
One-fifth the number of Fe^2+ ions that are consumed
A solution is prepared by adding 16g of CH3OH (molar mass 32g) to 90g of H2O (molar mass 18g). The mole fraction of CH3OH in this solution is closest to which of the following?
0.1
Has the highest electronegativity
Br
Occurs when aqueous solutions of ammonia and vinegar are mixed.
Brnsted-Lowry Acid-base reaction
Sodium chloride is LEAST soluble in which of the following liquids?
CCl4
Which of the following techniques is most appropriate for the recovery of the solid KNO3 from an aqueous solution of KNO3?
Evaporation to dryness
Which of the following molecules has the shortest bond length?
N2
Which of the following is the conjugate acid of NH2-?
NH3
A student places a sample of a pure metal in a crucible and heats it strongly in air. Data from the experiment are given in the table above. The final mass was determined after the sample was cooled to room temperature. Which of the following statements related to the experiment is correct?
The mass of the sample increased, so a chemical change occurred when bonds formed between the metal and another substance.
In his atomic theory, Dalton proposed that all atoms of a given element are identical. Which of the following observations provides the best evidence that the proposal is incorrect?
The mass spectrum of Cu has a peak at 63 amu and another peak at 65 amu
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 resulting solution conducts electricity
Four different liquid compounds in flasks at 20C 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 liquid.
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.
Two different ionic compounds each contain only copper and chlorine. Both compounds are powders, one white and one brown. An elemental analysis is performed on each powder. Which of the following questions about the compounds is most likely to be answered by the results of the analysis?
What is the formula unit of each compound?
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
Compared to the equilibrium vapor pressure of CH3OH(l) at 300K, the equilibrium vapor pressure of C2H5OH(l) at 300K is
lower because London dispersion forces among C2H5OH molecules are greater than those among CH3OH molecules
Solid carbon tetrachloride, CCl4 , is represented by the diagram above. The attractions between the CCL4 molecules that hold the molecules together in the solid state are best identified as
nonpolar covalent bonds
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
The original solution used to make the solutions for the standard curve was prepared by dissolving 2.60g of CoCl2 (molar mass 130g/mol) in enough water to make 100mL of solution. What is the molar concentration of the solution?
0.200M
If 0.40 mol of H2 and 0.15 mol of O2 were to react completely as possible to produce H2O, what mass of reactant would remain?
0.20g of H2
What is the maximum number of moles of Al2O3 that can be produced by the reaction of 0.40mol of Al with 0.40mol of O2
0.20mol
How many grams of CaCl2 (molar mass = 111g/mol) are needed to prepare 100mL of 0.100M Cl- ions?
0.555g
The melting point of MgO is higher than that of NaF. Explanations for this observation include which of the following? 1. Mg^2+ is more positively charged than Na+ 2. O^2- is more negatively charged than F- 3. The O^2- ion is smaller than the F- ion.
1 and 2 only
How many carbon atoms are contained in 2.8g of C2H4?
1.2 x 10^23
What is the bond orders of the nitrogen bonds?
1.5 and 1.5
2MnO4-(aq) + 10Br-(aq) + 16H+(aq) —> 2Mn^2+(aq) + 5Br2(aq) + 8H2O(l) How many electrons are transferred in the reaction represented by the balanced equation above?
10
When the equation above is balanced and all coefficients are reduced to their lowest whole-number terms, the coefficient for O2(g) is
12
What volume of O2(g) is required to react with excess CS2(l) to produce 4.0L of CO2(g)? Assume all gases are measured at 0C and 1 atm.
12L
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
Of the following electron configurations of neutral atoms, which represents an atom in an excited state?
1s2 2s2 2p5 3s2
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
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
An oxidation-reduction reaction that is also a synthesis reaction
2 Mg(s) + O2(g) —> 2 MgO(s)
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)
Aqueous solutions of barium chloride and silver nitrate are mixed to form solid silver chloride and aqueous barium nitrate. The balanced complete ionic equations contains which of the following terms?
2Ag+(aq)
Aqueous solutions of barium chloride and silver nitrate are mixed to form solid silver chloride and aqueous barium nitrate. The balanced molecular equation contains which one of the following terms?
2AgCl (s)
A sample of carbonate rock is a mixture of CaCO3 and MgCO3. The rock is analyzed in a laboratory, and the results are recorded in the table above. Which columns in the table provide all the information necessary to determine the mole ratio of Ca to Mg in the rock?
3,4,6,7
Which of the following is closest to the frequency of light with photon energy of 3.3 x 10^-19 J?
5.0 x 10^14 s^-1
Aqueous solutions of barium chloride and silver nitrate are mixed to form solid silver chloride and aqueous barium nitrate. The net ionic equation contains which of the following terms?
Ag+ (aq)
Which of the following name(s) is(are) correct? 1. Sulfide, S2- 2. Ammonium Chloride, NH4Cl 3. Acetic Acid, HC2H3O2 4. Barium Oxide, BaO
All
Which of the following diagrams best illustrates how a displacement in an ionic crystal results in cleavage and brittleness?
Before Displacement- four by four molecules equal in size After Displacement- half of the molecules shift down
Which of the following molecules is least soluble in water?
CCl4
Which of the following substances has the greatest solubility in C5H12(l) at 1atm?
CCl4(l)
On the basis of the information above, which of the following arranges the binary compounds in order of increasing bond polarity
CH4 < SiCl4 < SF4
The four species above have the same electron configuration 1s^2 2s^2 2p^6 3s^2 3p^6. Which of the following statements correctly identifies the species with the largest radius and provides an explanation based on coulomb's law?
Cl-
In another experiment, a small piece of Mg(s) is weighed, then placed in a flask containing excess 1 M HCl(aq). The student wants to determine number of moles of gas produced. Which of the following is the best way to conduct the experiment for accurate data collection?
Collecting the gas in a eudiometer tube and measuring the volume of the gas collected.
Has the largest atomic radius
Cs
Has the lowest first ionization energy
Cs
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
Which of the following compounds at 25C and 1.0 atm contains an element in a +1 oxidation state?
Cu2O
A mixture containing equal numbers of moles of ethyl acetate and butyl acetate was separated using distillation. Based on the diagrams shown above, which of the following identifies the substance that would be initially present in higher concentration in the distillate and correctly explains why that occurs?
Ethyl Acetate because it has a shorter carbon chain and weaker London Dispersion forces
Which of the following is the net ionic equation for the reaction between aqueous sodium fluoride and hydrochloride acid?
F-(aq) + H+(aq) —> HF(aq)
Steel is an alloy consisting of Fe with a small amount of C. Elemental Cr can be added to steel to make the steel less likely to rust: Cr atoms react with oxygen in the air to form a no reactive layer of chromium oxide on the surface of the steel, preventing the oxidation of underlying Fe atoms. A sample of steel-chromium alloy contains 15 percent Cr by mass. Which of the following diagrams best shows a particle level view of a surface section and an interior section of the allow represented below at the left?
First Diagram shows a mix of small O and C particles in between large Fe and Cr atoms. Second Diagram shows only small C particles between Cr and Fe
The maxwell Boltzmann distributions of molecular speeds in samples of two different gases at the same temperature are shown above. Which gas has the greater molar mass?
Gas A
Has two line pair of electrons
H2O
The liquified hydrogen halides have the normal boiling points given above. The relatively high boiling point of HF can be correctly explained by which of the following?
HF molecules tend to form hydrogen bonds.
Which of the following is paired incorrectly?
HNO3- weak acid
The diagram shown above shows the distribution of speeds for a sample of N2(g) at 25C. Which of the following graphs shows the distribution of speeds for a sample of O2(g) at 25C (dashed line)?
Higher dashed line quicker decline
A student finds the mass of a pure sample of a metal chloride hydrate. The student heats the sample several times, reaching a constant mass that contains 0.100 mole of anhydrous metal chloride. Which of the following questions about the hydrated metal chloride substance is most likely to be answered by the results of the experiment?
How many moles of water are in one mole of the substance?
Which of the following are oxidation-reduction reactions? 1. PCl3 + Cl2 —> PCl5 2. Cu + 2AgNO3 —> Cu(NO3)2 + 2Ag 3. CO2 + 2LiOH —> Li2CO3 + H2O 4. FeCl2 + 2NaOH —> Fe(OH)2 + 2NaCl
I and II
A student placed a piece of I2 in 50mL of H2O(l), another piece of I2 if the same mass in 50mL 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 H2O do not.
A 50mL sample of C6H14(l) is mixed with a 50mL sample of H2O(l) and the mixture is shaken vigorously. The two liquids do not stay mixed but instead form two separate layers. The density of hexane is 0.66g/mL and the density of water is 1g/mL. A 1g sample of I2(s) is added to the mixture which is shaken again. Which of the following best predicts what happens to the I2(s)?
I2 will be found mainly in the top layer because it will dissolve more in C6H14(l)
In the following reaction, which species is oxidized? 8NaI + 5H2SO4 —> 4I2 + H2S + 4NaSO4 + 4H2O
Iodine
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.
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.
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 of 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.
Based on the results of the paper chromatography experiment shown above, which of the following can be concluded about the dye?
It has a weaker attraction for the stationary phase than it has for the mobile phase.
Steel is an alloy containing Fe atoms and C atoms. Which of the following diagrams best represents the particle level structure of steel?
Large, white circles representing Fe atoms and small, gray circles representing C atoms in the gaps of the Fe atoms
The electron cloud of HF is smaller than that of F2, however HF has a much higher boiling point than F2. Which of the following explains how the dispersion force model of intermolecular attraction does not account for the unusually high boiling point of HF?
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.
Which statement best helps to explain the observation that NH3(l) boils at -28C whereas PH3(l) boils at -126C?
NH3 has hydrogen bonding that is stronger than the dipole-dipole forces in PH3
Which of the following compounds contains both ionic and covalent bonds?
NH4Cl
According to the complete photoelectron spectrum, which of the following is the identity of the element?
Ne
The photoelectron spectra above shows 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
Resonance is most commonly used to describe the bonding in molecules of which of the following?
O3
The reaction between solid copper and aqueous silver nitrate produces solid silver and a blue solution, as represented by the balanced equation shown above. Based on the balanced equation, which of the following identifies the oxidation and reduction half reactions?
Oxidation- Cu(s) —> Cu^2+(aq) + 2e^- Reduction- Ag^+(aq) + e^- —> Ag(s)
The decomposition of H2O2(aq) is represented by the equation above. A student monitored the decomposition of a 1.0L sample of H2O2(aq) at a constant temperature of 300K and recorded the concentration of H2O2 as a function of time. Which of the following identifies the element(s) being oxidized and reduced in the reaction?
Oxygen is both oxidized and reduced.
Consider atoms of the following elements. Assume that the atoms are in the ground state. The atom that contains exactly two unpaired electrons
S
A compound contains 30% sulfur and 70% flouring by mass. The empirical formula of the compound is
SF4
For which of the following molecules are resonance structures necessary to describe the bonding satisfactorily?
SO2
Which of the following ions has the same number of electrons as Br-?
Sr2+
Occur when solid sodium acetate, NaC2H3O2(s), is added to water
Sublimation
Under which of the following conditions of temperature and pressure would 1mol of the real gas CO2(g) behave most like an ideal gas?
Temperature- 800K Pressure- 1atm
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 mass spectrum of element X is presented in the diagram above. Based on the spectrum, which of the following can be concluded about element X?
The atomic mass of X is between 90 and 92
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 1 L sample of helium gas at 25C and 1 atm is combined with a 1 L sample of neon gas at 25C and 1 atm. 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.
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 table above shows the melting points of MgO and NaF. Which of the following best explains why the melting point of MgO is much higher than that of NaF?
The charges of Mg^2+ and O^2- ions are greater than those of Na+ and F- ions.
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.
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 2p sublevel have the smallest binding energy.
How many moles of Na+ ions are in 100 mL of 0.100M Na3PO4(aq)?
0.0300 mol
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.
has a central atom with less than an octet of electrons
BH3
Atoms of Mg combine with atoms of F to form a compound. Atoms of which of the following elements combine with atoms of F in the same ratio?
Ba
The molecule with only one double bond
C2H4
Which of the following molecules contains only single bonds?
C2H6
A student performed a fractional distillation of a mixture of two straight-chain hydrocarbons, C7H16 and C8H18. Using four clean, dry flasks, the student collected the distillate over the volume ranges (A, B, C, and D) shown in the graph above. Over what volume range should the student collect the distillate of the compound with the stronger intermolecular forces?
D
A student obtains a liquid sample of green food coloring that is known to contain a mixture of two solid pigments, one blue and one yellow, dissolved in an aqueous solution of ethanol. Which of the following laboratory setups is most appropriate for the student to use in order to separate and collect a substantial sample of each of the two pigments?
D. Picture with separate inks
Which of the following graphs correctly shows the relationship between potential energy and internuclear separation for two hydrogen atoms?
D. spike as internuclear separation becomes smaller
The diagram above shows a thin-layer chromatography of a mixture of products from a chemical reaction. The separation was performed using 50% ethyl acetate in hexane as the solvent (mobile phase) and silica gel as the polar stationary phase. On the basis of the chromatography and the information about solvents in the table above, which of the following would be the best way to decrease the distance that the products travel up the plate?
Decrease the percentage of ethyl acetate in the solvent.
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 then MgS because the coulombic attractions between its singularly charged Na+ ions and the Cl- ions are weaker than those between the ions in MgS.
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.
A precipitation reaction
Pb^2+(aq) + CrO4^2-(aq) —> PbCrO4(s)
forms monoatomic ions with 2^- charge in solutions
S
The mass percent of carbon in pure glucose, C6H12O6 is 40%. A chemist analyzes an impure sample of glucose and determines that the mass percent of carbon is 38.2%. Which of the following impurities could account for the low mass percent of carbon in the sample?
Water, H2O
When reaction 3 occurs, does the hybridization of the carbon atoms change?
Yes; it changes from sp to sp2
In the following diagrams, elements are represented by X and Z, which form molecular compounds with one another. Which diagram represents a molecule that has a bent molecular geometry?
Z:X:Z w/ 2 lone pairs on X
A particle level diagram of a metallic element is shown above. Typically, the 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 non directional bonds
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
forces among Br2 molecules are stronger than those among Cl2 molecules.
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
The geometry of the SO3 molecule is best described as
trigonal planar
