The potential energy as a function of internuclear distance for three diatomic molecules, X2, Y2, and Z2, is shown in the graph above. Based on the data in the graph, which of the following correctly identifies the diatomic molecules, X2, Y2, and Z2?

The lattice energy of a salt is related to the energy required to separate the ions. For which of the following pairs of ions is the energy that is required to separate the ions largest? (Assume that the distance between the ions in each pair is equal to the sum of the ionic radii.)

The most tightly bonded ions will be those with the highest oxidation number. Though Mg and Ca both have an oxidation number of 2+ , since Mg is the smaller ion (atom as well), it will have a smaller radius leading to a stronger bond and higher lattice energy.

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

The lone pair of N can be shared and both N and B will have an octet.

F and H can only form one bond and will not be able to bond twice as shown in the incorrect options.

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.

Which of the following is an isomer of CH₃OCH₃ ?

On the basis of the information above, which of the following arranges the binary compounds in order of increasing bond polarity?

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

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?

The bonding in compounds between elements with the same (or only slightly different) electronegativity values will exhibit covalent bonding (that is, more or less equal sharing of electrons).

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

In the solid state, the ions are held by strong coulombic forces in fixed positions within the lattice; thus they cannot move or migrate through the lattice.

The table above shows the structural formulas and molar masses for three different compounds. Which of the following is a list of the compounds in order of increasing boiling points?

Solid carbon tetrachloride, CCl₄(s), is represented by the diagram above. The attractions between the CCl₄

molecules that hold the molecules together in the solid state are best identified as

Carbon tetrachloride molecules have equivalent bonds that are symmetrically arranged around the carbon atom; thus, the bond dipoles cancel and the molecules are nonpolar. The attractions between molecules are London dispersion forces, which result from temporary dipoles.

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

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?

Which statement best helps to explain the observation that NH₃(l) boils at −28°C , whereas PH₃(l)boils at −126°C ?

It is the hydrogen bonding between molecules of NH3 that results in its boiling point being higher than the boiling point of PH3.

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 184oC, respectively?

Since both Br2 and I2 are nonpolar, London dispersion forces establish the boiling points. The larger electron cloud in I2 gives it a greater polarizability and therefore stronger London dispersion forces. The higher boiling point of I2 is therefore due to the greater polarizability of I2, as stated in this option.

Contains 1 sigma (σ) and 2 pi (π) bonds

Has a bond order of 2

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?

In a sample of a diatomic element, the only attractive forces present between the molecules are London dispersion forces. The model does not show the temporary fluctuating dipoles of the molecular electron clouds that are responsible for LDFs

LDFs.

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

Which of the following has a zero dipole mo­ment?

Which of the following species is NOT planar?

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?

The figure above shows that in solid hydrogen fluoride there are two different distances between H atoms and F atoms. Which of the following best accounts for the two different distances?

There is a shorter covalent bond between H and F within the molecules and longer hydrogen bond between the H in one molecule and the F in a second molecule.

Which of the following most likely describes the solid represented in the diagram above?

The boiling points of the elements helium, neon, argon, krypton, and xenon increase in that order. Which of the following statements accounts for this increase?

Which of the following molecules has an angular (bent) geometry that is commonly represented as a resonance hybrid of two or more electron-dot structures?

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?

The diagram above shows two resonance structures for a molecule of C₆H₆. The phenomenon shown in the diagram best supports which of the following claims about the bonding in C₆H₆ ?

Because of resonance, all the bonds between carbon atoms in C₆H₆ are equivalent and have the same strength and equal lengths.

Which of the following could be the identity of a white crystalline solid that exhibits the following properties?

• It melts at 320°C.
• It does not conduct electricity as a solid.
• It conducts electricity in an aqueous solution.

What is the hybridization of the carbon atoms in a molecule of ethyne, represented above?