Ap Chem Semester Exam

Which of the following diagrams best depicts an alloy of Ni and B

(A)

The particle-level diagram above represents the structure of solid KF. Although the molar mass of KCl is greater than that of KF, the density of KCl is actually less than that of KF. Which of the following representations of the structure of KCl best helps to explain this phenomenon?

(A) + - + - + - + - +

If 0.40 mol of H2 and 0.15 mol of O2 were to react as completely as possible to produce H2O, what mass of reactant would remain?

(A) 0.20 g of H2

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?

(A) 0.20 g of H2

How many carbon atoms are contained in 2.8 g of C2H4 ?

(A) 1.2 x 1023

If equal masses of the following compounds undergo complete combustion, which will yield the greatest mass of CO2?

(A) Benzene, C6H6

Which of the following lists Mg, P, and Cl in order of increasing atomic radius?

(A) Cl < P < Mg

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?

(A) Methane does not exhibit hydrogen bonding, but water does.

In a titration experiment, H2O2(aq) reacts with aqueous MnO4 - (aq) as represented by the equation above. The dark purple KMnO4 solution is added from a buret to a colorless, acidified solution of H2O2(aq) in an Erlenmeyer flask. (Note: At the end point of the titration, the solution is a pale pink color.)

(A) Oxygen, which changes from -1 to 0

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?

(A) The attractive and repulsive forces are balanced, so the atoms will maintain an average internuclear distance x

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

(A) forces among Br2 molecules are greater than those among Cl2 molecules

Potassium hydrogen phthalate, KHP, is used as a primary standard for determining the concentration of a solution of NaOH by titration. If the KHP has not been dried before weighing, the calculated molarity of the NaOH would be

(A) higher than the actual value, since water is included in the apparent mass of KHP

Refer to the following gaseous molecules: (A) BeCl2 (B) SO2 (C) N2 (D) O2 (E) F2 The geometry of the SO3 molecule is best described as

(A) trigonal planar

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?

(B) 0.033 M

A 23.0g sample of a compound contains 12.0g of C, 3.0g of H, and 8.0g of O. Which of the following is the empirical formula of the compound?

(B) C2H6O

Which of the following Lewis electron-dot diagrams represents the molecule that contains the smallest bond angle?

(B) F N F F

The molecule that has trigonal pyramidal geometry

(B) H2O

Which of the following elements has the mass spectrum represented above?

(B) Mo

Which of the following is the conjugate acid of NH2 - ?

(B) NH3

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?

(B) Na has a lower first ionization energy than Ne.Which of the following ground-state electron configurations represents the atom that has the lowest first-ionization energy?

Forms monatomic ions with 2- charge in solutions

(B) S

For which of the following molecules are resonance structures necessary to describe the bonding satisfactorily?

(B) SO2

Refer to the following gaseous molecules: (A) BeCl2 (B) SO2 (C) N2 (D) O2 (E) F2 Is a polar molecule:

(B) SO2

Refer to the following gaseous molecules: (A) BeCl2 (B) SO2 (C) N2 (D) O2 (E) F2 Is best represented by two or more resonance forms

(B) SO2

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?

(B) The atoms form a bond with a bond length of 75 pm

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?

(B) The carbon-to-selenium bond is nonpolar covalent.

At 127°C, the entire sample of I2 is observed to have vaporized. How does the mass of vessel 5 at 127°C compare to its mass at 27°C?

(B) The mass is the same, since the number of each type of atom in the vessel is constant

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?

(B) The mass of the sample increased, so a chemical change occurred when bonds formed between the metal and another substance.

A solution of a salt of a weak acid HY is added to a solution of another weak acid HX. Based on the information given above, which of the following species is the strongest base?

(B) Y−(aq)

A 2 mol 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

(B) the amount of OF2 (g) produced is halved.

How many moles of Na+ ions are in 100. mL of 0.100 M Na3PO4 (aq)?

(C) 0.0300 mol

A 2 L sample of N2(g) and a 1 L sample of Ar(g), each originally at 1 atm and 0°C, are combined in a 1 L tank. If the temperature is held constant, what is the total pressure of the gases in the tank?

(C) 3 atm

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?

(C) Ag+ (aq) + Ni (s) -> Ag (s) + Ni 2+ (aq)

Has a central atom with less than an octet of electrons

(C) BH3

If the pressure of each gas is increased at constant temperature until condensation occurs, which gas will condense at the lowest pressure?

(C) Butane

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 59oC and 184o C, respectively?

(C) I2 molecules have electron clouds that are more polarizable than those of Br2 molecules, thus London dispersion forces are stronger in liquid I2

A sample of an ideal gas is cooled from 50.0oC to 25.0oC in a sealed container of constant volume. Which of the following values for the gas will decrease?

(C) III only

Which of the following correctly indicates whether the solid represented by the particulate model shown above conducts electricity and explains why or why not?

(C) It does not conduct electricity because its ions cannot move freely within the solid.

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?

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

A compound contains 30. percent sulfur and 70. percent fluorine by mass. The empirical formula of the compound is

(C) SF4

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?

(C) The electron removed during the third ionization is, on average, much closer to the nucleus than the first two electrons removed were.

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?

(C) 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?

(C) The strength of the intermolecular forces between the particles in the liquids

All the chlorides of the alkaline earth metals have similar empirical formulas, as shown in the table above. Which of the following best helps to explain this observation?

(C) The two valence electrons of alkaline earth metal atoms are relatively easy to remove.

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?

(C) There is repulsion between paired electrons in oxygen's 2p orbitals.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?

A 1.0 L sample of a pure gas is found to have a lower pressure t

(C) are attracted to each other and do not exert as much force on the container walls as they would if they had no mutual attractions

The best explanation for the fact that diamond is extremely hard is that diamond crystals

(C) are giant molecules in which each atom forms strong covalent bonds with all of its neighboring atoms

The diagrams above represent solutes present in two different dilute aqueous solutions before they were mixed. Water molecules are not shown. When the solutions were combined, a precipitation reaction took place. Which of the diagrams below is the best particle representation of the mixture after the precipitation reaction occurred?

(D)

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?

(D) 14 mL

Which of the following ground-state electron configurations represents the atom that has the lowest first-ionization energy?

(D) 1s2 2s2 2p6 3s1

In which of the following processes are covalent bonds broken?

(D) C(diamond) → C(g)

Which of the following complete Lewis diagrams represents a molecule containing a bond angle that is closest to 120°?

(D) H O H C C O H H

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 if the temperature is lowered. Which of the following best describes how the model is limited in its depiction of the phenomenon?

(D) It does not show how the temporary fluctuating dipoles of the molecular electron clouds result in a net force of attraction between the molecules.

A student has a 1 g sample of each of the following compounds: NaCl, BKr, and KCl. Which of the following lists the samples in order of increasing number of moles in the sample?

(D) KBr < KCl < NaCl

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?

(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.

Which of the following scientific claims about the bond in the molecular compound HF is most likely to be true?

(D) The bond is highly polar.

A vessel contains Ar(g) at a high pressure. Which of the following statements best helps to explain why the measured pressure is significantly greater than the pressure calculated using the ideal gas law?

(D) The combined volume of the Ar atoms is too large to be negligible compared with the total volume of the container.

The elements in which of the following have most nearly the same atomic radius?

(E) Cr, Mn, Fe, Co

The liquefied 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?

(E) HF molecules tend to form hydrogen bonds.

The percentage of silver in a solid sample is determined gravimetrically by converting the silver to Ag+(aq) and precipitating it as silver chloride. Failure to do which of the following could cause errors in the analysis?

(E) I, III, and IV

Which of the following compounds contains both ionic and covalent bonds?

(E) NH4Cl