Mid Term Chem

B

In which of the following compounds is the mass ratio of chromium to oxygen closest to 1.62 to 1.00? A. CrO3 B. CrO2 C. CrO D. Cr2O E. Cr2O3

E

Is a strong electrolyte in aqueous solution: A. NH3(g) B. BH3(g) C. H2(g) D. H2S(g) E. HBr(g)

electronic transition

Ultraviolet and Visible

Molecular vibration

Infared

D

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? A. HCl(aq) and Cl−(aq) B. HCl(aq) and H3O+(aq) C. H2O(l) and H3O+(aq) D. H2O(l) and Cl−(aq)

D

Lewis electron-dot diagrams for CO2 and SO2 are given above. The molecular geometry and polarity of the two substances are A. the same because the molecular formulas are similar B. the same because C and S have similar electronegativity values C. different because the lone pair of electrons on the S atom make it the negative end of a dipole D. different because S has a greater number of electron domains (regions of electron density) surrounding it than C has

D

MgCl2(aq) + 2NaOH(aq) → 2NaCl(aq) + Mg(OH)2(s) A 100mL sample of 0.1M MgCl2(aq) and a 100mL sample of 0.2M NaOH(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? A. Using the same volume of MgCl2(aq)MgCl2(aq) but twice the volume of NaOH(aq) B.Using twice the volume of MgCl2(aq)MgCl2(aq) but half the volume of NaOH(aq) C.Using twice the volume of MgCl2(aq)MgCl2(aq) but the same volume of NaOH(aq) D. Using twice the volume of MgCl2(aq)MgCl2(aq) and twice the volume of NaOH(aq)

B

NH3(aq) + HCl(aq) ⇄ NH4+(aq) + Cl-(aq) The Brønsted-Lowry bases in the reaction represented above are A. NH3(aq) and NH4+(aq) B. NH3(aq) and Cl-(aq) C. NH3(aq) and HCl(aq D. HCl(aq) and NH4+(aq) E. HCl(aq) and Cl-(aq)

A

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? A. Yes; it changes from sp to sp2. B. Yes; it changes from sp to sp3. C. Yes; it changes from sp2 to sp3. D. No; it does not change

A

The London (dispersion) forces are weakest for which of the following gases under the same conditions of temperature and pressure? A. H2 B. O2 C. Xe D. F2 E. N2

B

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 3.3×10−19J. A. Red B. Orange C. Yellow D. Blue

C

The elements I and Te have similar average atomic masses. A sample that was believed to be a mixture of I and Te was run through a mass spectrometer, resulting in the data above. All of the following statements are true. Which one would be the best basis for concluding that the sample was pure Te? A. Te forms ions with a −2 charge, whereas I forms ions with a −1 charge. B. Te is more abundant than I in the universe. C. I consists of only one naturally occurring isotope with 74 neutrons, whereas Te has more than one isotope. D. I has a higher first ionization energy than Te does.

E

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 A. higher in container 1 because the surface area of the liquid is greater B. higher in container 1 because the volume of vapor is greater C. lower in container 1 because the level of the liquid is lower D. the same in both containers because the volume of the liquid is the same E. the same in both containers because the temperature is the same

A

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 < Y2 < Z2 A. X2 Y2 Z2 H2 N2 O2 B. X2 Y2 Z2 H2 O2 N2 C. X2 Y2 Z2 N2 O2 H2 D. X2 Y2 Z2 O2 H2 N2

B

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? A. Butane < 1-propanol < acetone B. Butane < acetone < 1-propanol C. 1-propanol < acetone < butane D.Acetone = butane < 1-propanol

C

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? A. Cu has two common oxidation states, but Ag has only one. B. Cu has a higher melting point than Au has, but Ag has a lower melting point than Au has. C. Cu atoms are smaller than Ag atoms, thus they interfere more with the displacement of atoms in the alloy. D. Cu atoms are less polarizable than are Au or Ag atoms, thus Cu has weaker interparticle forces.

Molecular rotation

microwave

B

. . . LiHCO3(aq) + . . . H2SO4(aq) → . . . Li2SO4(aq) + . . . H2O(l) + . . . CO2(g) When the equation above is balanced and the coefficients are reduced to lowest whole-number terms, what is the coefficient of H2O(l) ? A. 1 B. 2 C. 3 D. 4 E. 5

D

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? A. Na2SO4 is more soluble in water than NaCl is. B. Na2SO4 has a higher molar mass than NaCl has. C. To prepare a given volume of 0.10 M solution, the mass of Na2SO4 needed is more than twice the mass of NaCl needed. D. 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. E. The degree of dissociation of Na2SO4 in solution is significantly greater than that of NaCl.

B

A 0.35 g sample of Li(s) is placed in an Erlenmeyer flask containing 100 mL of water at 25°C. A balloon is placed over the mouth of the flask to collect the hydrogen gas that is generated. After all of the Li(s) has reacted with H2O(l), the solution in the flask is added to a clean, dry buret and used to titrate an aqueous solution of a monoprotic acid. The pH curve for this titration is shown in the diagram below Which of the following is the balanced net-ionic equation for the reaction between Li(s) and water? A. 2 Li(s) + 2 H+(aq) + 2 OH−(aq) → 2 Li+(aq) + 2 OH−(aq) + H2(g) B. 2 Li(s) + 2 H2O(l) → 2 Li+(aq) + 2 OH−(aq) + H2(g) C. 2 Li(s) + 2 H2O(l) → 2 LiOH(s) + H2(g) D. 2 Li(s) + 2 H2O(l) → 2 LiH(s) + H2(g)

D

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? A. The average speed of the helium atoms increases when the gases are combined. B. The average speed of the neon atoms increases when the gases are combined. C. The average kinetic energy of the helium atoms increases when the gases are combined. D. The average kinetic energy of the helium atoms and neon atoms do not change when the gases are combined.

C

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 A. unequally shared and form nondirectional bonds B. unequally shared and form highly directional bonds C. equally shared and form nondirectional bonds D. equally shared and form highly directional bonds

D

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. A wavelength of 510nm corresponds to an approximate frequency of 6×1014s−1. What is the approximate energy of one photon of this light? A. 9 × 10^47 J B. 3 x 10^17 J C. 5 x 10^-7 J D. 4 x 10^-19 J

C

Based on the data in the table above, which of the following liquid substances has the weakest intermolecular forces? A. C6H6(l) (VP: 75) B. C2H5OH(l) (VP: 44) C. CH3OH(l) (VP: 92) D. C2H6O2(l) (VP: 0.06)

B

Directions: Each set of lettered choices below refers to the numbered statement immediately following it. Select the one lettered choice that best fits the statement. A choice may be used once, more than once, or not at all. Refer to the following gaseous molecules: (A) BeCl2 (B) SO2 (C) N2 (D) O2 (E) F2 Is a polar molecule A. BeCl2 B. SO2 C. N2 D. O2 E. F2

C

Directions: Each set of lettered choices below refers to the numbered statements immediately following it. Select the one lettered choice that best fits each statement. A choice may be used once, more than once, or not at all in each set. (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

B

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? A. The resulting solution is colorless. B. The temperature of the reaction mixture increases. C. The total volume of the mixture is approximately equal to the sum of the initial volumes. D. The resulting solution conducts electricity.

A

On the basis of strength of intermolecular forces, which of the following elements would be expected to have the highest melting point? A. Br2 B. Cl2 C. F2 D. Kr E. N2

D

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? A. When the samples are combined, the gas particles will collide with one another, with the net effect being that the speed of the lowest energy particles decreases while the speed of the highest energy particles increases, leaving the average speed of the particles in the original samples unchanged. B. When the samples are combined, the gas particles from each sample will collide with the gas particles from the other sample until every particle in the mixture has the same speed, which is between the average speed of the particles in the hotter sample and the average speed of the particles in the cooler sample. C.When the samples are combined, the gas particles collide with one another until every particle in the mixture has the same kinetic energy, which is between the average kinetic energy of the particles in the hotter sample and the average kinetic energy of the particles in the cooler sample. D. 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

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. A. Volume B. Mass C. Velocity D. Attractions E. Shape

D

Which of the following correctly identifies which has the higher first-ionization energy, Cl or Ar, and supplies the best justification? A. Cl, because of its higher electronegativity B. Cl, because of its higher electron affinity C. Ar, because of its completely filled valence shell D. Ar, because of its higher effective nuclear charge

A

Which of the following lists Mg, P, and Cl in order of increasing atomic radius? A. Cl < P < Mg B. Cl < Mg < P C. Mg < P < Cl D. Mg < Cl < P E. P < Cl < Mg

A

Which of the following statements, if true, would support the claim that the NO3− ion, represented above, has three resonance structures? A. The NO3− ion is not a polar species. B. The oxygen-to-nitrogen-to-oxygen bond angles are 90°. C. One of the bonds in NO3− is longer than the other two. D. One of the bonds in NO3− is shorter than the other two.

A

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+ C. K+ D. Cl-