concepts

A plot of the number of neutrons versus the number of protons in nuclei shows a narrow band of stable isotopes. By what method(s) can isotopes with a low proton-neutron ratio (i.e., ones that fall below the band of stability) decay to form elements that are more stable? Answers: a) positron emission or electron capture. b) positron emission or neutron capture. c) beta emission or electron capture. d) gamma ray emission or beta emission. e) neutron capture or alpha emission.

a

All of the following statements are false for the freezing of water at 273 K EXCEPT Answers: a) DH < 0. b) DH > 0. c) DH = 0. d) DS = 0. e) DS > 0.

a

All of the following statements are true EXCEPT Answers: a) for a nuclear fission chain reaction to occur, one neutron must be produced for each one consumed. b) in a light water nuclear reactor, steam drives the turbines used to generate electricity. c) in a fission reactor, uranium 235 reacts with a neutron to produce more neutrons and products of lower mass. d) many of the fission products of uranium 235 are radioactive. e) one function of the water in a light water reactor is to slow down neutrons given off by fission.

a

All of the followings statements are true EXCEPT Answers: a) transition metal complexes are often colored, due to 3d to 1s electronic transitions. b) in low-spin complexes, electrons are concentrated in the lower-energy orbitals. c) low-spin complexes contain the minimum number of unpaired electrons. d) the crystal field splitting energy is small in high-spin complexes. e) the crystal field splitting energy of a metal complex can sometimes be determined from the absorption spectrum.

a

At 298 K, all of the following substances have a standard free energy of formation of zero EXCEPT ____. Answers: a) Br2(g) b) I2(s) c) S8(s) d) Cl2(g) e) Hg(l)

a

For a chemical reaction, DG and DG° are equal Answers: a) when products and reactants are in standard state concentrations. b) when K = 0. c) when K > 1. d) for a system at equilibrium. e) when the entropy change is zero.

a

How many geometric isomers may exist for the square-planar complex ion [Pt(OH)2(NH3)2]2-? Answers: a) 2 b) 3 c) 4 d) 5 e) 6

a

Identify the ligands and their charges in [Os(NH3)4Cl2]+. Answers: a) ammonia (no charge), chloride ion (charge = -1) b) chloride ion (charge = -1) c) ammonia (no charge) d) osmium (charge = +3) e) osmium (charge = +3), chloride ion (charge = -1)

a

If a nucleus emits an alpha particle, its mass number Answers: a) decreases by 4. b) decreases by 2. c) remains the same. d) increases by 1. e) decreases by 2.

a

Rubber elasticity is an entropic phenomenon. As a rubber band is stretched the entropy of the system Answers: a) is reduced. b) is increased. c) remains unchanged. d) breaks the polymer chain. e) causes chemical bonds to form.

a

The following reaction occurs spontaneously. 2Al(s) + 6H+(aq) ® 2Al3+(aq) + 3H2(g) Write the balanced oxidation half-reaction. Answers: a) Al(s) ® Al3+(aq) + 3e- b) Al3+(aq) + 3e- ® Al(s) c) H2(g) ® 2H+(aq) + 2e- d) 2H+(aq) + 2e- ® H2(g) e) 2H+(aq) ® H2(g) + 2e-

a

The second law of thermodynamics states that Answers: a) in a spontaneous process, there is a net increase in entropy, taking into account both the system and the surroundings. b)there is no disorder in a perfect crystal at 0 K. c) the total energy of the universe is always increasing. d) the total energy of the universe is constant. e) mass and energy are conserved in all chemical reactions.

a

The third law of thermodynamics states that Answers: a) there is no disorder in a perfect crystal at 0 K. b) in a spontaneous process, the entropy of the universe increases. c) the total entropy of the universe is always increasing. d) the total mass of the universe is constant. e) mass and energy are conserved in all chemical reactions.

a

What is the correct form for the Gibbs-Helmholtz equation? Answers: a) DG = DH - TDS b) DG = DH + TDS c) DH = DG - TDS d) DS = DH - TDG e) DG = DS - TDH

a

Which of the following half-reactions has been assigned a standard reduction potential of 0.00 V? Answers: a) 2H+(aq) + 2e- ® H2(g) b) Ag+(aq) + e- ® Ag(s) c) Hg2Cl2(s) + 2e- ® 2Hg(l) + 2Cl-(aq) d) Au3+(aq) + 3e- ® Au(s) e)Cu2+(aq) + 2e- ® Cu(s)

a

Write a balanced net ionic equation for the overall reaction represented by the cell notation below. Ag | AgI | I- || Fe2+, Fe3+ | Pt Answers: a) Fe3+(aq) + Ag(s) + I-(aq) ® Fe2+(aq) + AgI(s) b) Fe2+(aq) + Ag(s) + I-(aq) ® Fe3+(aq) + AgI(s) c) Fe3+(aq) + AgI(s) ® Fe2+(aq) + Ag(s) + I-(aq) d) Fe2+(aq) + AgI(s) ® Fe3+(aq) + Ag(s) + I-(aq) e) Fe3+(aq) + 2I-(aq) ® Fe2+(aq) + I2(s)

a

All of the following statements concerning voltaic cells are true EXCEPT Answers: a) a salt bridge allows cations and anions to move between the half-cells. b) electrons flow from the cathode to the anode in the external circuit. c) oxidation occurs at the anode. d) a voltaic cell can be used as a source of energy. e) a voltaic cell consists of two-half cells.

b

Given the following half-reactions, Pb(s) + 2I-(aq) ® PbI2(s) + 2e- I2(aq) + 2e- ® 2I-(aq) write the balanced overall reaction. Answers: a) Pb(s) + I2(aq) + 2e- ® PbI (s) + I-(aq) b) Pb(s) + I2(aq) ® PbI2(s) c) Pb(s) + Cl2(aq) ® Pb2+(aq) + 2I-(aq) d) 2Pb(s) + 4e- ® 2PbI(s) + I2(aq) e) Pb(s) + e- + 2I-(aq) ® PbI2(aq)

b

How many geometric isomers exist for [Fe(H2O)4(NH3)2]3+? Answers: a) 1 b) 2 c) 3 d) 4 e) 6

b

How many geometric isomers exist for [Fe(en)2(CN)2]+? Answers: a) 1 b) 2 c) 3 d) 4 e) 6

b

How many possible structures exist for the tetrahedral complex [Zn(en)3]2+? Answers: a) 1 b) 2 c) 3 d) 4 e) 6

b

If a reactant loses electrons it is Answers: a) reduced. b) oxidized. c) disproportionated. d) the cathode. e) a catalyst.

b

The complex FeF64- is paramagnetic. Which of the following set of terms best describes the complex? Answers: a) high-spin, Do large b) high-spin, Do small c) low-spin, Do large d) low-spin, Do small e) none of the above

b

Which of the following ligands causes the greatest splitting of d orbitals? Answers: a) H2O b) NO2- c) Cl- d) F- e) NH3

b

Write a balanced chemical equation for the overall reaction represented below. Cu | Cu2+ || Cl- | Hg2Cl2 | Hg Answers: a) 2Hg(l) + Cu2+(aq) + 2Cl-(aq) ® Hg2Cl2(s) + Cu(s) b) Correct Hg2Cl2(s) + Cu(s) ® 2Hg(l) + Cu2+(aq) + 2Cl-(aq) c) Hg2Cl2(s) ® 2Hg(l) + Cl2(aq) d) Hg2Cl2(s) + Cu(s) ® 2Hg(l) + Cu2+(aq) + Cl2(aq) e) 2Hg(l) + Cl2(aq) ® Hg2Cl2(s)

b

All of the following statements are true EXCEPT Answers: a) DS > 0 for systems that become more disorderly. b) reactions are spontaneous when DG < 0. c) reactions are spontaneous when DH < 0. d) DH < 0 for exothermic reactions. e) generally, nature tends to move from more ordered to more random states.

c

All of the following statements are true EXCEPT Answers: a) a reaction is spontaneous if DG < 0. b) if DG = 0, the system is at equilibrium. c) if DG = 0, then DS = DH. d) if DG > 0, then a reaction is not spontaneous. e) DG is referred to as Gibbs free energy.

c

All of the following statements are true EXCEPT Answers: a) gamma emission can accompany nuclear decay, such as beta emission. b) gamma rays can be used to extend the shelf life of food products. c) gamma rays have the same properties as electrons. d) gamma emission consists of high energy photons. e) gamma rays move at the speed of light.

c

Determine the number of unpaired electrons in the low-spin complex ion Cr(CN)64-. Answers: a) 0 b) 1 c) 2 d) 4 e) 5

c

For a spontaneous reaction, at constant pressure Answers: a) DG° > 0 and E° > 0. b) DG° > 0 and E° < 0. c) DG° < 0 and E° > 0. d) DG° < 0 and E° < 0. e) DG° = 0 and E° = 0.

c

For the lead storage battery, the products of the discharge reaction are Answers: a) Pb at the anode, H2O at the cathode. b) H2SO4 at the anode, H2O at the cathode. c) PbSO4 at both the anode and cathode. d) Pb at the cathode and PbO2 at the anode. e) Pb at both the anode and cathode.

c

Marie Curie was the first person in history to Answers: a) discover radioactivity. b) die from leukemia. c) win two Nobel Prizes. d) name an element. e) discover the neutron.

c

Predict the signs of DS and DH for the evaporation of water at 295 K. Answers: a) DH = 0 and DS > 0 b) DH > 0 and DS < 0 c) DH > 0 and DS > 0 d) DH < 0 and DS > 0 e) DH < 0 and DS < 0

c

The dissolution of ammonium nitrate occurs spontaneously in water at 25°C. As NH4NO3 dissolves, the temperature of the water decreases. What are the signs of DH, DS, and DG for this process? Answers: a) DH > 0, DS < 0, DG > 0 b) DH > 0, DS > 0, DG > 0 c) DH > 0, DS > 0, DG < 0 d) DH < 0, DS < 0, DG < 0 e) DH < 0, DS > 0, DG > 0

c

What are the possible formulas of all the tetracoordinate complex ions formed by copper(II) with NH3 and/or ethylenediamine (en) molecules as ligands? Selected Answer: Incorrect Cu(NH3)42+, Cu(en)2(NH3)42+, Cu(en)22+ Answers: a) Cu(NH3)42+, Cu(en)(NH3)32+, Cu(en)2(NH3)22+, Cu(en)3(NH3)2+, Cu(en)42+ b) Cu(NH3)42+, Cu(en)2(NH3)42+, Cu(en)22+ c) Cu(NH3)42+, Cu(en)(NH3)22+, Cu(en)22+ d) Cu(NH3)62+, Cu(en)2(NH3)22+, Cu(en)32+ e) Cu(NH3)42+, Cu(en)22+

c

What is the oxidation number of the copper in [Cu(NH3)3Cl]NO3? Answers: a) 0 b) +1 c) +2 d) +4 e) +5

c

Which of the following statements concerning entropy is/are CORRECT? 1. The entropy of a substance increases when converted from a liquid to a solid. 2. The entropy of a substance decreases as its temperature increases. 3. All substances have positive standard molar entropies at temperatures above 0 K. Answers: a) 1 only b) 2 only c) 3 only d) 1 and 2 e) 1, 2, and 3

c

Write a balanced chemical equation for the overall reaction represented below. Pt | Fe2+, Fe3+ || Cl- | AgCl | Ag Answers: a) AgCl(s) + Fe3+(aq) + 2e- ® Ag(s) + Fe2+(aq) + Cl-(aq) b) AgCl(s) + Fe3+(aq) ® Ag(s) + Fe2+(aq) + Cl-(aq) c) AgCl(s) + Fe2+(aq) ® Ag(s) + Fe3+(aq) + Cl-(aq) d) Ag(s) + Fe3+(aq) + Cl-(aq) ® AgCl(s) + Fe2+(aq) e) Ag(s) + Fe2+(aq) + Cl-(aq) ® AgCl(s) + Fe3+(aq)

c

All of the following complexes will be colored (in the visible) EXCEPT ____. Answers: a) [Co(en)3]2+ b) [Fe(CN)6]4- c) [Ni(H2O)6]2+ d) [Sc(NH3)6]3+ e) [Cu(NH3)4]2+

d

Determine the number of unpaired electrons in an octahedral, high-spin Cr(II) complex. Answers: a) 1 b) 2 c) 3 d) 4 e) 5

d

For the decomposition of hydrogen peroxide to water and oxygen, H2O2(g) ® H2O(g) + mc040-1.jpgO2(g) DH° = -106 kJ, and DS° = +0.0580 kJ/K. In what temperature range is the reaction spontaneous (DG° < 0)? Answers: a) The temperature must be greater than 1.83 ´ 103 K. b) The temperature must be less than 1.83 ´ 103 K. c) The temperature must be between 225 K and 1.83 ´ 103 K. d) DG° is always less than zero. e) DG° is never less than zero.

d

Fuel cells are being researched as a possible replacement for the internal combustion engine (ICE) in automobiles. What is/are the advantages of using a fuel cell/electric motor in place of the (ICE) in an automobile? Answers: a) H2 fuel cells only produce H2O vs. (ICE) produces NO(g) and CO2(g). b) Fuel cells are more efficient. c) Fuel cells are less expensive. d) both a and b. e) all of the above.

d

If a chemical reaction has a negative change in entropy, DS, then Answers: a) the reaction is endothermic. b) the reaction is spontaneous. c) the equilibrium constant is greater than 1. d) there is an increase in the order of the system. e) the change in Gibbs free energy, DG, is negative.

d

The following processes occur spontaneously at 25°C. Which of these processes is/are endothermic? 1. NH4NO3 dissolving in water (which is accompanied by a cooling of the water). 2. the expansion of a real gas into a vacuum (which is accompanied by a cooling of the gas). 3. liquid water in an ice cube tray freezing into ice after being placed in a freezer. Answers: a) 1 only b) 2 only c) 3 only d) 1 and 2 e) 1, 2, and 3

d

What is the electron configuration for Fe3+? Answers: a) 1s22s22p63s23p63d54s1 b) 1s22s22p63s23p63d44s2 c) 1s22s22p63s23p63d6 d) 1s22s22p63s23p63d5 e) 1s22s22p63s23p63d7

d

What is the formula for dicyanobis(ethylenediamine)zirconium(IV) nitrate? Answers: a) Zr[(CN)2(NO3)2(en)2] b) [Zr(CN)2(NO3)2(en)2] c) (NO3)2[Zr(CN)2(en)2] d) [Zr(CN)2(en)2](NO3)2 e) [Zr(NO3)2(en)2](CN)2

d

When 6 ligands approach a central metal atom along the x-, y- and z-axes, they will cause the d orbitals to split in energy. The dx2-dy2 and the dx2 orbitals are most affected because Answers: a) the electron density in these orbitals is squared. b) unlike the other d orbitals, these orbitals contain unpaired electrons. c) unlike the other d orbitals, these orbitals each contain a pair of electrons. d) they have the highest electron density along the x-, y-, and z-axes, and thus feel the greatest repulsion from the ligands' unpaired electrons. e) the shape of these orbitals is similar to that of the ligands' orbitals.

d

Which of the following are conditions for the standard Gibbs free energy? 1. Ions or molecules in solution are present at one molar concentrations. 2. Gases are present at one atmosphere partial pressure. 3. The temperature of the system is 273 K. Answers: a) 1 only b) 2 only c) 3 only d) 1 and 2 e) 1, 2, and 3

d

All of the following events result in an increase in entropy EXCEPT Answers: a) the melting of candle wax. b) the combustion of carbon. c) the dissolution of sodium chloride in water. d) the evaporation of ethanol. e) the formation of N2O4(g) from NO2(g).

e

All of the following statements are true EXCEPT Answers: a) a nucleus weighs less than the protons and neutrons from which it is composed. b) the difference in mass between a nucleus and its individual protons and neutrons is called the mass defect. c) the process in which a nucleus decomposes to form two or more lighter nuclei is called nuclear fission. d) nuclear fission evolves more energy than ordinary chemical reactions, such as the combustion of gasoline. e) nuclear fission evolves more energy than nuclear fusion.

e

An extremely sensitive method has recently been developed for measuring carbon14 concentrations in organic materials. What is this method? Answers: a) acid titration b) nuclear magnetic resonance c) gas chromatography d) atomic absorption spectrometry e) mass spectrometry

e

If DG is positive at all temperatures, then which of the following statements must be true? Answers: DH < 0 and DS < 0 DH < 0 and DS = 0 DH < 0 and DS > 0 DH > 0 and DS > 0 Correct DH > 0 and DS < 0

e

If a chemical reaction is exothermic, but not spontaneous, which of the following must be true? Answers: a) DG > 0, DS > 0 and DH > 0 b) DG < 0, DS > 0 and DH > 0 c) DG > 0, DS < 0 and DH > 0 d) DG < 0, DS < 0 and DH < 0 e) DG > 0, DS < 0 and DH < 0

e

In a gas phase reaction, what is the effect of increasing reactant or product pressure on the standard Gibbs free energy, DG°? Answers: a) DG° increases due to decreased entropy. b) DG° decreases due to decreased entropy. c) DG° increases due to increased enthalpy. d) DG° may either increase or decrease. e) DG° is unchanged.

e

J. Willard Gibbs, professor at Yale from 1871 to 1903, Selected Answer: Incorrect was a theoretician, who studied chemical thermodynamics. Answers: a) was a researcher, experimenting with high energy reactions. b) was a theoretician, who studied chemical thermodynamics. c) received no salary for the first ten years. d) both a and c. e) both b and c.

e

The anode is where Answers: a) electrolyte concentrations are lowest. b) electrolyte concentrations are highest. c) the Nernst potential is measured. d) anions are produced. e) oxidation occurs.

e

The cell voltage, E°, is ____ for a reaction taking place in a voltaic cell. Answers: a) reductive b) oxidative c) negative d) zero e) positive

e

The following reaction occurs spontaneously. 2 Fe(s) + 3 Cl2(aq) ® 2 Fe3+(aq) + 6 Cl-(aq) Write the balanced reduction half-reaction. Answers: a) Fe(s) ® Fe3+(aq) + e- b) Fe(s) + 3 e- ® Fe3+(aq) c) Fe(s) + 3/2 Cl2(aq) ® FeCl3(aq) d) Cl2(aq) ® 2 Cl-(aq) + 2 e- e) Cl2(aq) + 2 e- ® 2 Cl-(aq)

e