AP Chem Midterm (Units 1-4)

Which of the following best represents the ground-state electron configuration for an atom of Bromine? A) 1s2 2s2 2p6 3s2 3p6 4s2 4d10 4p5 B) 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 C) 1s2 2s2 2p6 3s2 3p6 4s2 4d10 4p6 D) 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5

?? (Not A) D most likely?

Solid carbon tetrachloride, CCl4 , is represented by the diagram at right. The attractions between the CCL4 molecules that hold the molecules together in the solid state are best identified as A) Polar covalent bonds B) Nonpolar covalent bonds C) intermolecular attractions resulting from temporary dipoles D) intermolecular attractions resulting from permanent dipoles

?? (Not B)

The distribution of speeds of H2(g) molecules at 273 K and 1 atm is shown in the diagram above. Which of the following best shows the speed distribution of He(g) atoms under the same temperature and pressure conditions? A) The particle is positively charged, because the oxygen atoms in water are attracted to it. B) The particle is negatively charged because hydrogen atoms in water are attracted to it. C) The particle is both positively and negatively charged, because the water molecules are attracted to it. D) The particle is neutral because the dipoles of the water molecules neutralize the charge of the particle.

?? (Not B) ***

Which of the following diatomic species contains 1 sigma bond and 2 pi bonds? A) Li2 B) B2 C) N2 D) O2 E) F2

?? (Not B) maybe N2?

Which of the following best helps to account for the fact that the F- ion is smaller than the O2- ion? A) F- has a larger nuclear mass than O2- has B) F- has a larger nuclear charge than O2- has C) F- has more electrons that O2- has D) F- is more electronegative than O2- is E) F- is more polarizable than O2- is

?? (Not D) maybe B?

What kind of physical or chemical change occurs when solid sodium acetate, NaC2H3O2(s), is added to water? A) Oxidation-reduction reaction B) Broasted-Lowry acid-base reaction C) Sublimation D) Dehydration E) Precipitation

??? (Not D)

What kind of physical or chemical change occurs when ammonia and vinegar are mixed? A) Oxidation-reduction reaction B) Broasted-Lowry acid-base reaction C) Sublimation D) Dehydration E) Precipitation

??? Maybe B?

Which of the following has two lone pair of electrons? A) H20 B) NH3 C) BH3 D) CH4 E) SiH4

A) H20

A mixture of H2(g) and O2(g) is placed in a container as represented above. The H2(g) and O2(g) react to form H2O(g). Which of the following best represents the container after the reaction has gone to completion? (4H2, 4O2) A) 4H2O B) 4H2O + 2O2 C) 4H2O + 2O D) 8H2O

B) 4H2O + 2O2 ***

Based on the results of the paper chromatography experiment shown above, which of the following can be concluded about the dye? A) It has a small molar mass. B) It has weak intermolecular forces. C) It has a weaker attraction for the stationary phase than it has for the mobile phase. D) It has a stronger attraction for the stationary phase than it has for the mobile place.

C) It has a weaker attraction for the stationary phase than it has for the mobile phase.

A student obtains a sample of a pure solid compounds. 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? A) Mass of the sample, density of the sample B) Mass of the sample, volume of the sample C) Molar mass of the compound, mass of the sample D) Molar mass of the compound, density of the sample

C) Molar Mass of the compound, mass of the sample

Which of the following can be inferred from the diagram above that shows the dependence of potential energy on the internuclear distance between two atoms? A) The atoms form a bond with a bond length of 25pm B) The net force between the atoms is attractive at 25pm C) The atoms form a bond with a bond length of 75pm D) The net force between the atoms is attractive at 75pm

C) The atoms form a bond with a bond length of 75pm

Another sample of eggshell reacts completely with 4.0mL of an HCl(aq) solution of unknown concentration. If the reaction produces 0.095 atm of gas, the concentration of the HCl(aq) solution was at least A) 0.0020M B) 0.050M C) 0.50M D) 1.0M

D) 1.0M ***

Which of the following is true regarding the reaction represented below? H2Se(g) + 4O2F2(g) -> SeF6(g) + 2HF(g) + 4O2(g) A) The oxidation number of O does not change. B) The oxidation number of H changes from -1 to +1. C) The oxidation number of F changes from -1 to +1. D) The oxidation number of Se changes from -2 to +6. E) It is a disproportionation reaction for F.

D) The oxidation number of Se changes from -2 to +6.

The average kinetic energy of the gas molecule is A) Greatest in container A B) Greatest in container B C) Greatest in container C D) The same in all three containers

D) The same in all three containers

In a paper chromatography experiment, a sample of a pigment is separated into two components, X and Y, as shown in the figure above. The surface of the paper is moderately polar. What can be concluded about X and Y based on the experimental results? A) X has a larger molar mass than Y does. B) Y has a larger molar mass than X does. C) X is more polar than Y. D) Y is more polar than X.

D) Y is more polar than X.

The potential energy as a function of internuclear distance for three diatomic molecules, H2, O2, and N2, is shown in the graph to the right. Based on the data in the graph, identify the diatomic molecules H2, O2, and N2 X2 = ___ Y2 = ___ Z2 = ___

H2, N2, O2 ***

The temperature of the CH3OH is increased from 300K to 400K to vaporize all the liquid, which increases the pressure in the vessel to 0.30 atm. The experiment is repeated under identical conditions but this time using half the mass of CH3OH that was used originally. What will be the pressure in the vessel at 400K? A) 0.15 atm B) 0.30 atm C) 0.40 atm D) 0.60 atm

A) 0.15 atm

On the basis of the information above, which of the following arranges the binary compounds in order of increasing bond polarity? [ (Element - Electronegativity) H - 2.1 , C - 2.5 , S - 2.5 , F - 4.0 , Cl - 3.0 , Si - 1.8 ] A) CH4 < SiCl4 < SF4 B) CH4 < SF4 < SiCl4 C) SF4 < CH4 < SiCl4 D) SiCl4 < SF4 < CH4

A) CH4 < SiCl4 < SF4

A partial-level diagram of a metallic element is shown below. Typically, metals are both malleable and ductile. The best explanation for these properties is that the electrons involved in bonding among metals are: (Metal: A "Sea of Electrons) A) Equally shared and form nondirectional bonds B) Equally shared and form directional bonds C) Unequally shared and form nondirectional bonds D) Unequally shared and form highly directional bonds

A) Equally shared and form nondirectional bonds ***

The Bronsted-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) NH3(aq) and NH4+(aq)

The distribution of speeds of H2(g) molecules at 273 K and 1 atm is shown in the diagram above. Which of the following best shown the speed distribution of He(g) atoms under the same temperature and pressure conditions? A) Tall and Left of the original graph B) Tall and Right of the original graph C) Below the original graph D) Short and Right of the original graph

A) Tall and Left of the original graph ***

The student made the standard curve above. Which of the following most likely caused the error in the point the student plotted at 0.050M Co2+(aq)? A) There was distilled water in the corvette when the student put the standard solution in it. B) There were a few drops of the 0.100M Co2+(aq) standard solution in the corvette when the student put the 0.050M standard solution in it. C) The student used a corvette with a longer path length than the cuvette used for the other standard solutions. D) The student did not run a blank between the 0.050M Co2+(aq) solution and the one before it.

A) There was distilled water in the corvette when the student put the standard solution in it. ***

Of the three solutions listed in the table above, which one, if any, has the greatest electrical conductivity and why? A) 0.1M HC2H3O2(aq) because its molecules have the most atoms B) 0.1M KI(aq) because KI completely dissociates in water to produce ions C) 0.1M CH3OH(aq) because its molecules can form hydrogen bonds D) All three solutions have the same electrical conductivity because the concentrations are the same

B) 0.1M KI(aq) because KI completely dissociates in water to produce ions ***

Which of the following is ground state electron configuration of the S2- ion? A) 1s2 2s2 2p6 B) 1s2 2s2 2p6 3s2 3p6 C) 1s2 2s2 2p6 3s2 3p4 D) 1s2 2s2 2p6 3s2 3p2

B) 1s2 2s2 2p6 3s2 3p6

Which of the following equations best represents the species that react and the species that are produced when CaCO3(s) and HCl(aq) are combined? A) 2H+(aq) + CaCO3(s) -> Ca2+(aq) + CO3^2-(aq) + H2(g) B) 2H+(aq) + CaCO3(s) -> Ca2+(aq) + H2O(l) + CO2(g) C) 2H+(aq) + CaCO3(s) -> Ca2+(aq) + 2OH-(aq) + CO(g) D) 2HCl+(aq) + CaCO3(s) -> Ca2+(aq) + H2O(l) + CO2(g) + 2Cl-(aq)

B) 2H+(aq) + CaCO3(s) -> Ca2+(aq) + H2O(l) + CO2(g)

The mass spectrum of a sample of a pure element is shown below. Based on the data, the peak at 11 amu represents an isotope of which of the following elements? A) Na with 11 neutrons B) B with 6 neutrons C) C with 5 neutrons D) Cu with 11 neutrons

B) B with 6 neutrons

Of the following diagrams, which best represents the structure of KF? A) 4 electrons in a square alternating with 4 protons in a square B) Each electron alternating with each proton C) Protons in a straight line, Electrons in a straight line: alternating lines D) Protons and Electrons are spread out

B) Each electron alternating with each proton ***

The density of the gas, in g/L, is A) Greatest in container A B) Greatest in container B C) Greatest in container C D) The same in all three containers

B) Greatest in container B

Which of the following describes the changes in forces of attraction that occur as H2O changes phase from a liquid to a vapor? A) H-O bonds break as H-H and O-O bonds form. B) Hydrogen bonds between H2O molecules are broken. C) Covalent bonds between H2O molecules are broken. D) Ionic bonds between H+ ions and OH- ions are broken. E) Covalent bonds between H+ ions and H2O molecules become more effective.

B) Hydrogen bonds between H2O molecules are broken.

The melting point of MgO is higher than that of NaF. Explanations for this observation include which of the following: I. Mg2+ is more positively charged than Na+ II. O2- is more negatively charged than F- III. The O2- ion is smaller than the F- ion A) II only B) I and II only C) II and III only D) I, II, and III

B) I and II only

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? A) It has the formula XZ2 B) It contains ionic bonds C) It contains covalent bonds D) It dissolves in water

B) It contains ionic bonds

Which of the following is the conjugate acid of NH2-? A) NH2- B) NH3 C) H+ D) NH4+

B) NH3

Resonance is most commonly used to describe the bonding in molecules of which of the following? A) CO2 B) O3 C) CH4 D) BeF2 E) OF2

B) O3

The Elements N and Cl have the same electronegative value, 3.0. Which of the following claims about the compound forms from N and Cl is most likely to be true? A) The nitrogen to chlorine bond is unstable B) The nitrogen to chlorine bond is nonpolar covalent C) The nitrogen to chlorine bond is polar covalent D) A molecule of the compound will have a partial negative charge on the chlorine atom

B) The nitrogen to chlorine bond is nonpolar covalent

Which of the following has a central atom with less than an octet of electrons? A) H2O B) NH3 C) BH3 D) CH4 E) SiH4

C) BH3

If the pressure of each gas is increased at a constant temperature until condensation occurs, which gas will condense at the lowest pressure? A) Methane B) Ethane C) Butane D) All the gases will nonsense at the same pressure

C) Butane

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 1.00g/mL. A 1.0g 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)? A) I2 will be found mainly in the top layer because it will dissolve more in the H2O(l). B) I2 will be found mainly in the bottom layer because it will dissolve more in the H2O(l). C) I2 will be found mainly in the top layer because it will dissolve more in the C6H14(l). D) I2 will be found mainly in the bottom layer because it will dissolve more in the C6H14(l).

C) I2 will be found mainly in the top layer because it will dissolve more in the C6H14(l).

Which of the following ground-state electron configurations represents the atom that has the lowest first-ionization energy? A) 1s2 2s2 2p6 B) 1s2 2s2 2p1 C) 1s2 2s2 D) 1s2 2s2 2p6 3s2

D) 1s2 2s2 2p6 3s2

The diagram at right represents H2(g) and N2(g) in a closed container. Which of the following diagrams would represent the results if the reaction shown below were to proceed as far as possible? N2(g) + 3H2(g) -> 2NH3(g) A) 2NH3 B) 2HN3 + 2N2 C) 2HN3 + 2H2 D) 2NH3 + 2N2 E) 2NH3 + 3H2 + N2

D) 2NH3 + 2N2

A wavelength of 510nm corresponds to an approximate frequency of 6x10^14s-1. What is the approximate energy of one photon of this light? A) 9x10^47J B) 3x10^17J C) 5x10^-7J D) 4x10^-19J

D) 4x10^-19J

When the equation for the reaction represented below is balanced, and all coefficients are reduced to the lowest whole-number terms, the coefficient for O2(g) is: __C3H8(g) + __O2(g) -> __H2O(l) + __CO2(g) A) 1 B) 2 C) 3 D) 5 E) 6

D) 5

Which of the following best describes the change that takes place immediately after the CH3OH(l) is introduced into the previously evacuated vessel? A) A chemical change takes place because covalent bonds are broken. B) A chemical change takes place because intermolecular attractions are overcome. C) A physical change takes place because covalent bonds are broken. D) A physical change takes place because intermolecular forces are overcome.

D) A physical change takes place because intermolecular forces are overcome. ***

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 the 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? A) The solution does not change color after stirring. B) The KCl crystals are no longer visible after mixing with water. C) There is a temperature change in the solution during the dissolving process. D) After the water has evaporated, the white crystals in the beaker have a mass of 20.0g.

D) After the water has evaporated, the white crystals in the beaker have a mass of 20.0g.

The exothermic process represented above is best classified as a A) Physical change because a new place appears in the products B) Physical change because O2(g) that was dissolved comes out of solution C) Chemical change because entropy increases as the process proceeds D) Chemical change because covalent bonds are broken, and new covalent bonds are formed

D) Chemical change because covalent bonds are broken, and new covalent bonds are formed

RbCl has a high boiling point. Which of the following compounds is also likely to have a high boiling point, and why? A) NO, because its elements are in the same period of the periodic table B) ClF, because its elements are in the same group of the periodic table C) Cl2O, because its elements have similar electronegativities and it is a covalent compound D) CsCl, because its elements have very different electronegativities and it is an ionic compound

D) CsCl, because its elements have very different electronegativities and it is an ionic compound

Which of the following best helps to explain why hexane has a higher boiling point than methanol has? A) Methanol molecules can form hydrogen bonds with other methanol molecules. B) Hexane cannot form hydrogen bonds with other hexane molecules. C) Methanol molecules have attractions to one another due to London dispersion forces. D) Hexane molecules have electron clouds that are larger than those of methanol molecules.

D) Hexane molecules have electron clouds that are larger than those of methanol molecules.

The complete photoelectron spectrum for an element is shown below. Which of the following observations would provide evidence that the spectrum is consistent with the atomic model of the element? A) A neutral atom of the element with exactly 3 electrons B) The element does not react with other elements C) In its ionic compounds, the element tends to form ions with a charge of +4 D) In its ionic compounds, the element tends to form ions with a charge of -2

D) In its ionic compounds, the element tends to form ions with a charge of -2

A Student has a 1g sample of each of the following compounds: LiCl, KBr, and NaCl. Which of the following lists the samples in order of increasing number of moles in the sample? A) NaCl < LiCl < KBr B) NaCl < KBr < LiCl C) LiCl < NaCl < KBr D) KBr < NaCl < LiCl

D) KBr < NaCl < LiCl

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? A) Region X = Molecular Vibration ; Region Y = Molecular Rotation ; Region Z = Electronic Transition B) Region X = Electronic Transition ; Region Y = Molecular Rotation ; Region Z = Molecular Vibration C) Region X = Molecular Rotation ; Region Y = Molecular Vibration ; Region Z = Electronic Transition D) Region X = Electronic Transition ; Region Y = Molecular Vibration ; Region Z = Molecular Rotation

D) Region X = Electronic Transition ; Region Y = Molecular Vibration ; Region Z = Molecular Rotation ***

hen a buret is rinsed before a tradition, which of the techniques below is the best procedure? A) Rinse the buret one time with some of the titrant solution. B) Rinse the buret one time with some of the titrant solution and then dry the buret in an oven. C) Rinse the buret two times: once with some of the titrant solution, then once with distilled water. D) Rinse the buret two times: each time with some of the titrant solution. E) Rinse the buret two times: each time with distilled water.

D) Rinse the buret two times: each time with some of the titrant solution.

A 5.0g sample of MgCl2 may contain measurable amounts of other compounds as impurities. Which of the following quantities are needed to determine that the sample is pure MgCl2? A) The color and density of the sample B) The mass of Mg on the sample only C) The number of moles of Cl in the sample only D) The mass of Mg and the mass of Cl in the sample

D) The mass of Mg and the mass of Cl in the sample