APCHEM Unit 2 Test

Rank the bonds formed between O–C, Cl–Ca, N–S, and O–Si in order of increasing ionic character.

N–S < O–C < O–Si < Cl–Ca

N–S < O–C < Cl–Ca < O–Si

Cl–Ca < O–Si < O–C < N–S

O–C < N–S < O–Si < Cl–Ca

N–S < O–C < O–Si < Cl–Ca

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

Element	Electronegativity
H	2.1
C	2.5
S	2.5
F	4.0
Cl	3.0
Si	1.8

CH₄ < SF₄ < SiCl₄

SiCl₄ < SF₄ < CH₄

SF₄ < CH₄ < SiCl₄

CH₄ < SiCl₄ < SF₄

CH₄ < SiCl₄ < SF₄

Why does MgCl₂ (2326 kJ/mol) have a stronger lattice energy than LiCl (834 kJ/mol)?

There are twice as many chlorine ions in MgCl₂ compared to LiCl and it requires more energy to make twice as many bonds.

The Mg ion has a 2+ charge which is twice the charge of the lithium ion, causing the attraction with the chlorine ion to be stronger.

The Li ion has a smaller ionic radius that the Mg ion so it has a weaker attraction to the chlorine ions

The Mg ion has a larger ionic radius than the Li ion so it has a stronger attraction to the chlorine ions

The Mg ion has a 2+ charge which is twice the charge of the lithium ion, causing the attraction with the chlorine ion to be stronger.

What is the main factor contributing to the difference in lattice energies in the lithium halogen compounds on the table?

Bond	Lattice Energy (KJ/mol)
LiF	1030
LiCl	834
LiI	730

The bond order

The electronegativity values

The size of the halogen ion

The charge of the ions

The size of the halogen ion

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. O^2- is more negatively charged than F^-.

III. The O^2- ion is smaller than the F^- ion.

I, II, and III

I and III only

I and II only

II only

II and III only

I and II only

The potential energy of a system of two atoms as a function of their internuclear distance is shown in the diagram. Which of the following is true regarding the forces between the atoms when their internuclear distance is x?

 

It cannot be determined whether the forces between atoms are balanced, attractive, or repulsive, because the diagram shows only the potential energy.

There is a net attractive force pulling the atoms together, so the atoms will move closer together.

There is a net repulsive force pushing the atoms apart, so the atoms will move further apart.

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

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

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

NaI

NaCl

NaBr

NaF

All of the following are properties of solid ionic compounds, EXCEPT:

Conducts electricity

Dissolves in water

Forms a crystal lattice

Brittle structure

Conducts electricity

Solids have many different properties. _________ solids are known for their ability to be flattened into a sheet, stretched into a wire, and to conduct electricity well.

network

metallic

molecular

ionic

metallic

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

delocalized

temporary

localized

permanent

delocalized

What is the hybridization of Br in BrF₃?

sp³d²

sp³

sp²

sp³d

sp³d

Which of the following molecules has the shortest bond length?

Br₂

I₂

N₂

Cl₂

O₂

N₂

Which species has a trigonal-pyramidal molecular geometry?

SiH₄

BH₃

CH₄

H₂O

NH₃

NH₃

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

  

  

incorrect

Which gaseous molecule is a polar molecule

N₂

F₂

SO₂

BeCl₂

O₂

SO₂

Which gaseous molecule is best represented by two or more resonance forms

N₂

SO₂

F₂

BeCl₂

O₂

SO₂

The geometry of the SO₃ molecule is best described as  

trigonal planar

tetrahedral

trigonal pyramidal

square pyramidal

bent

trigonal planar

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

SO₃

CO₂

N₂

C₂H₂

HCN

C₂H₂

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? 

The N – C – C bond angle is 180°.

The leftmost C atom and all the atoms directly bonded to it lie in the same plane.

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

The geometry around the N atom is planar. 

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

Which of the following has a zero dipole moment?

SO₂

HCN

PF₅

NH₃

NO₂

PF₅

Which molecule has trigonal pyramidal geometry?

CO₂

PH₃

H₂O

CH₄

C₂H₄

PH₃

Which element follows the duet rule?

He

C

Ne

O

He

Select the answer that best fits the statement: Is isomeric with CH₃CH₂CHO.

CH₃CH₂CH₂CH₃

CH₃COCH₃

CH₃CH₂CH₂NH₂

CH₃CH₂CH₂OH

CH₃COOH

CH₃COCH₃

What is the formal charge on each atom in the N₂O Lewis structure below, read from left to right?

0, +1, -1

0, 0, 0

0, +1, 0

+1, 0, -1

0, +1, -1

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

1 and 2

2 and 2

1.5 and 1.5

1 and 1.5

1.5 and 1.5

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

  

Carbon has 4 valence electrons so the hydrogen atoms can bond equally

All of the hydrogen atoms have the same 1s orbital so they all bond the same

All the bonding atoms are identical so they take up the same amount of space

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

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

What is the molecular geometry of phosphine, PH₃?

Tetrahedral

Trigonal Pyramidal

Linear

Bent

Trigonal Pyramidal

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

CO₂

CN

C₂H₄

C₆H₆

CH₄

CH₄

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

CO

CO₂

F₂

HF

O₂

HF

Which of the following diatomic species has the largest bond-dissociation energy

Li₂

F₂

B₂

O₂

N₂

N₂

Which of the following diatomic species contains 1 sigma (σ) and 2 pi (π) bonds

F₂

B₂

N₂

O₂

Li₂

N₂

Which of the following species is NOT planar?

NO₃^-

CO₃^2-

ClF₃

PCl₃

BF₃

PCl₃

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

different because the lone pair of electrons on the S atom make it the negative end of a dipole

the same because C and S have similar electronegativity values

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

the same because the molecular formulas are similar

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

Which of the following is a nonpolar molecule that contains polar bonds?

NH₃

CHF₃

CO₂

F₂

HCl

CO₂

A Lewis diagram for the molecule C₂H₄ is shown in the figure. In the actual C₂H₄ molecule, the H-C-H bond angles are closest to

120°

180°

109.5°

90°

120°

Which of the following molecules is nonpolar but has polar covalent bonds?

H₂O

CCl₄

N₂

CH₂Cl₂

H₂O₂

CCl₄

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

O₂ < N₂ < F₂

N₂ < O₂ < F₂

N₂ < F₂ < O₂

F₂ < O₂ < N₂

F₂ < O₂ < N₂

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

Copper atoms and zinc atoms have the same atomic radius, 135 picometers. Based on this information, which of the following diagrams best represents an alloy containing only copper and zinc atoms?

Which of the following diagrams best illustrates how a displacement in an ionic crystal results in cleavage and brittleness?