AP Chem Final

NH3 reacts with BF3 to form a single species Which of the following structural diagrams in most likely representation of the product of the reaction?

(the one with 3 H's on N, N is connected to B, and B has 3 F's)

When 4.0 L of He(g), 6.0 L of N2(g), and 10.L of Ar(g), all at 0 degrees C and 1.0 atm, are pumped into an evacuated 8.0 L rigid container, the final pressure in the container at 0 degrees C is

2.5 atm

(question with absorbance and concentration graph with FeSCN2+) If the absorbance of the mixture is 0.20 at 453 nm, how many moles of Fe3+ (aq) were present in the 100. mL sample? (Assume that any volume change due to adding the KSCN (s) is negligible.)

4 x 10^-6

The first ionization energy of an element is the energy required to remove an electron from a gaseous atom of the element (i.e. X(g) --> X+(g) + e-). The values of the first ionization energies for the third row elements are shown in the graph above. On the basis of the information given, which of the following reactions is exothermic?

Al(g) + Mg+(g) --> Al+(g) +Mg(g)

In the reaction represented above, what is the hybridization of the C atoms before and after the reaction occurs?

Before: sp2 After: sp3

Based on the structures shown above, which of the following statements identifies the compound with the higher boiling point and provides the best explanation for the higher boiling point?

Compound 2, because it forms hydrogen bonds, whereas compound 1 does not

The complete photoelectron spectra of neutral atoms of two unknown elements, X and Y, are shown above. Which of the following can be inferred from the data?

Element Y has a greater nuclear charge than element X does

Which of the following has the bonds arranged in order of decreasing polarity?

H - F > N - F > F- F

Ne, HF, C2H6, CH4 Which of the substances listed above has the highest boiling point, and why?

HF, because its molecules form hydrogen bonds

Based on the diagram above, which of the following best helps to explain why MgO(s) is not able to conduct electricity, but MgO(l) is a good conductor of electricity? (diagram with solid and liquid of MgO)

MgO(s) consists of separate Mg2+ ions and O2- ions held in a fixed lattice, but in MgO (l) the ions are free to move and conduct electricity

The ideal gas law best describes the properties of which of the following gases at 0 degrees C and 1 atm?

N2

On the basis of molecular structure and bond polarity, which of the following compounds is most likely to have the greatest solubility in water?

NH3

NO2(g) + CO(g) --> NO(g) + CO2(g) The reaction between NO2 and CO(g) is represented above. The elementary steps of a proposed mechanism are represented below: (steps) Which of the following is the rate law for the overall reaction that is consistent with the proposed mechanism?

Rate=k[NO]^2

(with reactions A-D) The reactions represented above are carried on in sealed, rigid containers and allowed to reach equilibrium. If the volume of each container is reduced from 1.0 L to 0.5 L at constant temperature, for which of the reactions will the amount of products be increased?

Reaction A

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

SO3

A student is given a sample of a pure, white crystalline substance. Which of the following would be most useful in providing data to determine if the substance is an ionic compound?

Testing the electrical conductivity of an aqueous solution of the substance

Cl- + ClO- + 2H+ --> Cl2 + H2O What effect will increasing [H+] at constant temperature have on the reaction represented above?

The frequency of collisions between H+ ions and ClO- ions will increase

A sample of a solid labeled as NaCl may be impure. A student analyzes the sample ad determines that it contains 75 percent chlorine by mass. Pure NaCl(s) contains 61 percent chlorine by mass. Which of the following statements is consistent with the data?

The sample contains NaCl (s) and LiCl (s)

The mass spectrum of an average sample of a pure element is shown in the figure above. Which of the following is the identity of the element? (one with majority of 90, some 92, and some 94 amu)

Zr

At 298 k and 1 atm, Br2 is a liquid with a high vapor pressure, and Cl2 is a gas. Those observations provide evidence that under the given conditions, the

forces among Br2 molecules are stronger than those among Cl2 molecules

(low and high carbon steel) The table aboce provides some information about two types of steel, both of which are alloys of iron and carbon. Which of the following best helps to explain why high-carbon steel is more rigid than low carbon steel?

the additional carbon atoms within the alloy make it more difficult for the iron atoms to slide past one another