AP Chemistry Unit 2 Test

Rank the following bonds from nonpolar to most polar: 

H–I 

H–H

H–Cl

H–F

H–Br

H–H < H–I < H–Br < H–Cl < H–F

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

NH4Cl

Put the following bonds in order from strongest to weakest bond energy.

Bond	Bond Length (pm)
C-C	154
C-N	147
C-O	143
C-F	133

C–F > C–O > C–N > C–C

Which of the following provides the best explanation for why H–F has a higher bond energy (562 kJ/mol) than H–Br (366kJ/mol)?

Fluorine has a smaller atomic radius and bigger electronegativity value so it can pull the electrons in closer creating a stronger bond

Which of the following can be inferred from the diagram that shows the dependence of potential energy on the internuclear distance between two atoms?

 

The atoms form a bond with a bond length of 75 pm.

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).

Mg2+(g) and O2-(g)

Using the table of lattice energies, predict which ionic compound will have the highest melting point?

Ionic Compound	Lattice Energy (kJ/mol)
NaBr	732
NaF	910
NaI	632
NaCl	765

NaF

Which of the following arrangements does a basic cubic crystal lattice follow?

ABABAB

The energy required to dissociate an ionic solid into gaseous ions (lattice energy) for the compounds NaF and MgF₂ is shown in the table. On the basis of Coulomb's law, which of the following best helps to explain the large difference between the lattice energies of NaF and MgF₂?

 

Compound	Lattice Energy (kJ/mol)
NaF	930
MgF2	2978

The charge of the Mg cation is larger than that of the Na cation.

The characteristic of covalent bonds present in the metallic structure is that they are:

delocalized

In rose gold, some of the gold atoms are replaced by copper to make the metal stronger. This is an example of a(n):

Substitutional alloy

Steel is an alloy containing Fe atoms and C atoms. Which of the diagrams best represents the particle-level structure of steel?

 

What is the hybridization of Br in BrF₃?

sp3d

Which of the following has a zero dipole moment?

PF5

Which species has a trigonal-pyramidal molecular geometry?

NH3

The structural formula of the glycinium cation is shown in the figure. Arrows indicate the pK_a values for the labile protons in the molecule. What is the approximate H – O – C bond angle in the glycinium cation?

 

105

Which of the molecules represented below contains carbon with sp²hybridization?

C2H2Cl2

Lewis electron-dot diagrams for CO₂ and SO₂ are given. The molecular geometry and polarity of the two substances are

different because S has a greater number of electron domains (regions of electron density) surrounding it than C has

The geometry of the SO₃ molecule is best described as

trigonal planar

Pi (π) bonding occurs in each of the following species EXCEPT

CH4

In the 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?

 

Which of the following molecules has the shortest bond length?

N2

In the reaction represented by the figure, which of the following sets correctly identifies the hybridization of the C atoms before and after the reaction occurs?

 

 

Table: Before & After Sets

Set	Before	After
A	sp2	sp2
B	sp2	sp3
C	sp3	sp2
D	sp3	sp3

Set B

Which of the following is the correct lewis structure for nitrate, NO₃^-1

Which of the molecules contains only single bonds?

C2H6

Which atom is most likely to have the odd electron in NO₂?

Nitrogen because it is less electronegative and it will have a formal charge of +1

Based on the resonance structures shown, what are the bond orders of the two carbon-oxygen bonds?

 

1.5 and 1.5

Why do all of the H–C–H bonds in methane have the same bond angle?

Carbon's valence shell s and p orbitals hybridized to make four identical sp³ orbitals

Use the Lewis structure below to explain why CF₄ is non-polar.

The tetrahedral molecular shape of CF₄ allows the dipoles to cancel

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?

Unlike BF₃, NF₃ has a nonplanar geometry due to an unshared pair of electrons on the N atom.

The structural formula of the glycinium cation is shown in the figure. Arrows indicate the pK_a values for the labile protons in the molecule. Which statement is true about the geometry of the glycinium cation?

 

Both C atoms and both O atoms lie in the same plane

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

increasing number of unshared pairs of electrons

Of the following molecules, which has the largest dipole moment?

HF

Which of the following arranges the molecules N₂, O₂, and F₂ in order of their bond enthalpies, from least to greatest?

F2 < O2 < N2

Lewis diagrams of molecules of three different hydrocarbons are shown in the figure. Which of the following claims about the molecules is best supported by the diagrams?

 

The strongest carbon-to-carbon bond occurs in molecule 3.

Based on the diagram shown, which of the following would have the greatest dipole moment, and why?

 

 

PCl₃, because the Cl atoms draw electron density away from the P atom and the bond dipoles do not cancel one another.

Which of the following has molecules with a pyramidal shape?

NH3

Which of the following molecules contains exactly three sigma (σ) bonds and two pi (π) bonds?

C2H2

Which species is predicted to have the largest bond angle?

BH3

Which of the following Lewis electron-dot diagrams represents the molecule that is the most polar?