Comprehensive Assessment Of Chemical Bonding And Molecular Structure Practice Tests

Question 1

An unknown compound X has a melting point of $850^{\circ}C$ and conducts electricity only when dissolved in water. Which of the following represents the most likely chemical formula for X?

Accepted Answer

MgCl_{2}

Answer

CO_{2}

Answer

SiO_{2}

Answer

Fe

Question 2

In a metallic bond, the electrical conductivity is primarily due to the movement of localized valence electrons that are restricted to specific atomic nuclei.

Accepted Answer

False

Answer

True

Question 3

Determine the total number of valence electrons available for the Lewis structure of the carbonate ion, $CO_{3}^{2-}$.

Accepted Answer

24

Answer

22

Answer

26

Answer

20

Question 4

Calculate the total number of valence electrons for the molecule $N_{2}H_{4}$ and determine how many lone pairs are present in its final Lewis structure.

Accepted Answer

14 valence electrons and 2 lone pairs

Question 5

Which of the following substances exhibit properties consistent with the 'sea of electrons' model?

Answer

Cu

Answer

NaCl

Answer

Al

Answer

Fe

Answer

CH_{4}

Question 6

When drawing the Lewis structure for $SO_{2}$, if the central sulfur atom is bonded to two oxygen atoms with single bonds, how many electrons remain to be distributed as lone pairs after accounting for the bonds?

Accepted Answer

14

Answer

12

Answer

16

Answer

18

Question 7

For the polyatomic ion $NH_{4}^{+}$, calculate the total valence electron count used to draw the structure.

Accepted Answer

8

Question 8

In the Lewis structure of $N_{2}$, how many electrons are shared between the two nitrogen atoms to satisfy the octet rule?

Accepted Answer

6

Answer

2

Answer

4

Answer

8

Question 9

For the cyanate ion $OCN^-$, calculate the formal charge on the central carbon atom in the resonance structure where the oxygen atom has a formal charge of $-1$ and the nitrogen atom has a formal charge of $0$.

Accepted Answer

0

Question 10

Consider the molecule $SF_6$. Determine the number of electrons surrounding the central sulfur atom and identify the classification of this bonding exception.

Accepted Answer

12 electrons; hypervalent

Answer

8 electrons; octet rule compliant

Answer

10 electrons; hypervalent

Answer

14 electrons; incomplete octet

Question 11

In the resonance hybrid of ozone ($O_3$), the bond order for each oxygen-oxygen bond is exactly 1.5.

Accepted Answer

True

Answer

False

Question 12

Which of the following species exhibit an incomplete octet or are odd-electron radicals?

Answer

BH_3

Answer

SF_6

Answer

NO

Answer

AsF_5

Question 13

Calculate the formal charge on the central atom in $AsF_5$ assuming all bonds are single bonds and the central atom has no lone pairs.

Accepted Answer

0

Question 14

Given two resonance structures for $N_2O$ (N-N-O), structure A has formal charges $(N: -1, N: +1, O: 0)$ and structure B has formal charges $(N: -2, N: +1, O: +1)$. Based on formal charge stability rules, which is more stable?

Accepted Answer

Option A

Answer

Option B

Answer

Option C

Answer

Option D

Question 15

Given the following enthalpy values (in $kJ/mol$): Sublimation of $Na(s) = 108$, Ionization energy of $Na(g) = 496$, Bond dissociation of $Cl_2(g) = 242$, Electron affinity of $Cl(g) = -349$, and Lattice energy of $NaCl(s) = -787$. Calculate the standard enthalpy of formation $\Delta H_f^{\circ}$ for $NaCl(s)$ using the Born-Haber cycle.

Accepted Answer

-410 kJ/mol

Question 16

Rank the following ionic compounds in order of increasing lattice energy magnitude: $MgO$, $NaCl$, $LiF$.

Accepted Answer

$NaCl < LiF < MgO$

Answer

$LiF < NaCl < MgO$

Answer

$MgO < LiF < NaCl$

Answer

$NaCl < MgO < LiF$

Question 17

Using the average bond energies ($C-H = 413$, $C-C = 348$, $C=C = 614$, $H-H = 436$ in $kJ/mol$), calculate the enthalpy change $\Delta H$ for the hydrogenation of ethene: $C_2H_4(g) + H_2(g) \rightarrow C_2H_6(g)$.

Accepted Answer

-124 kJ/mol

Question 18

Which of the following bonds exhibits the highest degree of ionic character based on electronegativity differences ($\chi$)?

Accepted Answer

$Cs-F$ ($\chi_{Cs}=0.7, \chi_{F}=4.0$)

Answer

$N-F$ ($\chi_{N}=3.0, \chi_{F}=4.0$)

Answer

$C-F$ ($\chi_{C}=2.5, \chi_{F}=4.0$)

Answer

$Li-F$ ($\chi_{Li}=1.5, \chi_{F}=4.0$)

Question 19

For a series of diatomic molecules with the same bond order, the bond length is inversely proportional to the sum of the atomic radii of the bonded atoms.

Accepted Answer

False

Answer

True

Question 20

Which of the following factors contribute to a more exothermic (more negative) lattice energy for an ionic crystal lattice?

Answer

Smaller ionic radii

Answer

Higher ionic charges

Answer

Larger ionic radii

Answer

Lower ionic charges

Comprehensive Assessment Of Chemical Bonding And Molecular Structure Practice Tests

Practice Tests

Comprehensive Assessment of Chemical Bonding and Molecular Structure

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