AP Chem Final

The ionization energies of an unknown element, X, are listed in the table below. Which of the following is most likely empirical formula of a compound formed from element X and phosphorus, P? Ionization Energy (kJ/mol) First- 730 Second- 1450 Third- 7700 Fourth- 10,500

6. X3P2

Has two lone pairs of electrons

A. H2O

Has a central atom with less than an octet of electrons

C. BH3

The distrubution of speeds of H2 (g) molecules at 273K 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 conditions of temperature and pressure?

a

Use the four equations below for the following two questions. Choose the equation that represents an oxidation reaction that is also a synthesis reaction

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

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. 0.200 M

How many grams of CaCl2 (molar mass 111 g/mol) are needed to prepare 100 mL of 0.100 M Cl- (aq) ions?

a. 0.555 g

There are several different potential lewis diagrams for the sulfate ion two of which are below. What is the overall bond order shown in structure B

a. 1.5

Which of the following molecules has the largest dipole moment?

a. Br--F

A 0.5 mol sample of He(g) and a 0.5 mol sample of Ne(g) are placed separately in two 10.0 L rigid containers at 25°C. Each container has a pinhole opening. Which of the gases, He(g) or Ne(g), will escape faster through the pinhole and why?

a. He(g) will escape faster because the He(g) atoms are moving at a higher average speed than the Ne(g) atoms.

A student placed a sample of a food coloring that contains a mixture of a blue dye and a red dye at the top of a chromatography column filled with a nonpolar stationary phase. When water is poured through the column, two bands of colors are seen in the column, as shown in the diagram above. Which of the following techniques would be best to investigate molecular vibrations in molecules of the red dye?

a. Infrared spectroscopy

Which of the following molecules has the shortest bond length?

a. N2

Which has a pyramidal shape?

a. NH3

In the reaction above, NH4+(aq) acts as a weak acid. Which of the following must be true?

a. NH3 is a strong conjugate base

Which of the following best helps explain why the pressure of a sample of CH4(g) (molar mass 16 g/mol) is closer to the pressure predicted by the ideal gas law than a sample of NH3(g) (molar mass 17 g/mol)?

a. NH3 molecules are polar while Ch4 molecules are not, and the greater attractions between NH3 molecules cause the molecules to collide with the walls of the container with less force.

Equal numbers of moles of He(g), Ar(g), and Ne(g) are placed in a glass vessel at room temperature. If the vessel has a pinhole-sized leak, which of the following will be true regarding the relative values of the partial pressures of the gases remaining in the vessel after some of the gas mixture has effused?

a. PHe < PNe < PAr

Consider atoms of the following elements. Assume that the atoms are in the ground state. Choose the atom that contains exactly 2 unpaired electrons.

a. S

If a pure sample of an oxide of sulfur contains 40 percent sulfur and 60 percent oxygen by mass, then the empirical formula of the oxide is

a. SO3

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 intermolecular distance is B?

a. the attractive and repulsive forces are balanced, so the atoms will maintain an average internuclear distance at B

The average mass, in grams, of one mole of carbon atoms is equal to

a. the average mass of a single carbon atom, measured in amus

Choose the equation that represents a precipitation reaction

b

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-reaction?

b

Which of the following molecules is least soluble in water?

b

when a 3.22 g sample of an unknown hydrate of sodium sulfate, Na2SO4 xH2O is heated, H2O (molar mass 18 g) is driven off. the mass of the anhydrous Na2SO4 (molar mass 142 g) that remains is 1.42 g. the value of x in the hydrate is

b. 10

The complete photoelectron spectrum of an element is given above. Which of the following electron configurations is consistent with the spectrum?

b. 1s1 2s2 2p6 3s2 3p3

Which of the following best represents the electron configuration for an atom of sulfur?

b. 1s2 2s2 2p6 3s

Which of the following lists the correct number of protons, neutrons, and electrons (in that order) of a neutral cesium-134 atom?

b. 55, 79, 55

In 1.00 mol of potassium zirconium sulfate trihydrate, K4Zr(SO4)4 x 3H2O, there are

b. 6.02 x 20^23 sulfur atoms

A student prepared four solutions of known [Cu2+] and measured the absorbance of each solution using the same cuvette. The graph shows the data for the two absorbance measurements done for each solution. Which of the following identifies the most likely error that affected the absorbance recorded for the solution with [Cu2+]= 7x 10-3 M in the second trial?

b. A fingerprint was left on the side of the curvette facing the detector.

Which of the following correctly identifies which has the higher first ionization energy, Cl or Ar, and supplies the best justification?

b. Ar, because of its higher effective nuclear charge.

Ionization Energy (kJ/mol) First- 801 Second- 2,430 Third- 3,660 Fourth- 25,000 Fifth- 32,820 The first five ionization energies of a second-period element are listed in the table above. Which of the following correctly identifies the element and best explains the data in the table?

b. B, because it has three valence electrons.

A sample of a compound known to consist of only carbon, hydrogen, and oxygen is found to have a total mass of 29.05g. If the mass

b. C3H6O

What mass of oxygen is in 148 grams of calcium hydroxide (Ca(OH)2)?

b. C3H6O

Salts containing halide ions are soluble except for those containing silver, lead, and mercury. Salts containing carbonate anions are insoluble excepts for those containing alkali metals and ammonuim. If solutions of iron (III) nitrate and sodium carbonate are mixed, what would be the formula of the precipitate?

b. Fe2(CO3)3

A student places a peice of I2(s) in 50.0 mL of H2O another piece of I2(s) of the same mass in 50.0 mL of C6H14(l) and shakes the mixtures. The results are shown above. What do the results indicate about the intermolecular interactions of the substances?

b. I2 and C6H14 have similar intermolecular interactions, and I2 and H2O do not

1s12s2sp63s23p3 Atoms of an element, X, have the electronic configuration shown above. The compound most likely formed with magnesium, Mg, is:

b. Mg3X2

According to the information in the table below, a 1.00 g sample of which of the following contains the greatest mass of oxygen? Na2O- 62.0 MgO- 40.3 K2O- 94.2 CaO- 56.1

b. MgO

Which of the following Lewis diagrams best represents the bonding in the N2O molecule, considering formal charges?

b. N--N-O

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

b. NH3

In the reaction represented above, which of the following sets correctly identifies the hybridization of the C atoms before and after the reaction occurs? Set, Before, After A. sp2, sp2 B. sp2, sp3 C. sp3, sp2 D. sp3, sp3

b. Set B

Which of the following correctly identifies a Bronstead-Lowry conjugate acid-base pair in a solution prepared by mixing together HNO2(aq) and NH3(aq)?

b. The acid is HNO2, and the conjugate base is NO2-(aq)

A student has two dilute, colorless solutions, HCl(aq) and NaOH(aq), which were at the same temp. The student combined the solutions, and the reaction represented above occured. Which of the following results would be evidence that a chemical reaction took place?

b. The temperature of the reaction mixture increases

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?

b. Z:X:Z

The F-B-F bond angle in the BF3 molecule is

c. 120

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 x 10-19 J. Which of the following is closest to the frequency of the light with the photon energy of 3.3 x 10-19 J?

c. 5.0 x 10^14 s-1

A gas mixture at 0C and 1.0 atm contains 0.10 mol of H2, 0.015 mol of O2, and 0.025 mol of N2. Assuming ideal behavior, what is the partial pressure of hydrogen gas (H2) in the mixture?

c. About 0.20 atm because H2 comprises 20% of the total number of moles of gas.

The compound CCl4 is nonflammable and was once commonly used in fire extinguishers. On the basis of periodic properties, which of the following compounds can most likely be used as a fire resistant chemical?

c. CrB4

Consider atoms of the following elements. Assume that the atoms are in the ground state. The atom that contains only one electron in the highest occupied energy sublevel

c. Ga

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? I. The average molecular mass of the gas II. The average distance between the molecules III. The average speed of the molecules

c. III only

Based on the results of the paper chromatography experiment shown above, which of the following can be concluded about the dye?

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

Which of the following represents a process in which a species is reduced?

c. NO3-(aq)-->NO(g)

Which of the following ions has the same number of electrons as Br-?

c. Sr2-

What geometrical arrangement is associated with orbitals that are sp3 hybridized?

c. trigonal planar

Which of the following is based net ionic equation for an oxidation-reduction reaction between Ag+(aq) and Ni(s) based on the half-reactions represented above?

d

Which of the following is the net ionic equation for the reaction between aqueous sodium fluoride and hydrochloric acid?

d

What is the molarity of I-(aq) in a solution that contains 34g of SrI2 (molar mass 341 g) in 1.0 L of the solution?

d. 0.20 M

An experiment was performed to investigate the reaction between Zn metal and Ni2+ (aq) at different concentrations. Because the Ni2+ (aq) ion is green, the extent of the reaction was determined using spectrophotometric analysis. Four 20.0 mL standard solutions of Ni2+ (aq) were prepared by dissolving NiCl2*6H2O in water. The absorbance of each solution was measured; the results are shown both in the table below and in following plot of the absorbance data. What is expected absorbance of a standard solution made by dissolving 0.0070 mol of NiCl2*6H2O in water to make 100. mL of solution.

d. 0.45

An equimolar mixture of N2(g) and Ar(g) is kept inside a rigid container at a constant temperature of 300 K. The initial partial pressure of Ar in the mixture is 0.75atm. An additional amount of Ar was added to the container, enough to double the number of moles of Ar gas in the mixture. Assuming ideal behavior, what is the final pressure of the gas mixture after the addition of the Ar gas?

d. 2.25 atm, because doubling the number of moles of Ar doubles its partial pressure

Ca3(PO4)2(l)+H3PO4(l)-> Ca(H2PO4)2(s)

d. 4

A wavelength of 510 nm corresponds to an approximate frequency of 6 x 10^14 s^-1. What is the approximate energy of one photon of this light?

d. 4x10^-19 J

In which of the following compounds is the oxidation number of chromium the greatest?

d. 64 grams

Which element has the highest electronegativity?

d. Br

Which of the following molecules contains polar covalent bonds but is a nonpolar molecule?

d. CCl4

Which of the following compounds contain an element in a +1 oxidation state, before you balance according to subscripts?

d. Cu2O

Due to the presence of FeS(s) as an impurity, the combustion of some types of coal results in the formation SO2, as represented by the equation above. Which of the following statements is correct when 2.0 mol of FeS(s) reacts with 4.0 of O2(g)?

d. FeS(s) is the limiting reactant and 0.5 mol of O2(g) remains unreacted

In general, do metals or nonmetals from the same period have higher ionization energies? Why?

d. Nonmetals have higher ionization energies because they are closer to having filled a complete energy level.

To determine the percentage of water in a hydrated salt, a student heated 1.2346g sample of the salt for 30 minutes; when cooled to room temperature, the sample weighed 1.1857g. After the sample was heated for an additional 10 minutes and again cooled to room temperature, the sample weighed 1.1632g. Which of the following should the student do next?

d. Reheat the sample until its mass is constant

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

Why does an anion of phosphorous have a larger radius than a neutral atom of phosphorus?

d. The electrons in the anion have a greater repulsion than those in the neutral atom

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?

d. Unlike Bf3, NF3 has a nonpolar geometry due to an unshared pair of electrons on the N atom.

According to the VSEPR model, the progressive decrease in the bond angles in the series of the molecules CH4, NH3, and H2O is best accounted for by the:

d. increasing number of unshared pairs of electrons

Refer to three gases in identical rigid containers under the conditions given in the table below. 40. The average kinetic energy of the gas molecules is 41. The density of the gas, in g?l, is

d. the same in all containers b. greatest in container B