CHEM 133 Final Exam Study Questions Lessons 4-7 | American Public University

CHEM133
Final Exam Study Questions
Lessons 4-7


Lesson 4

1. Consider the following reaction:

A2 + B2 → 2AB ΔH = –321 kJ
Bond energy (A2) = 1/2AB
Bond energy (B2) =393 kJ/mol.

What is the numerical value for Bond energy (A2) ?

Question options:

 554 kJ/mol
 714 kJ/mol
 -161 kJ/mol
 238 kJ/mol

2. Element A has an electronegativity of 0.8 and element B has an
electronegativity of 3.0. Which statement best describes the bonding in
A3B?

Question options:

 The compound is largely ionic with A as the anion.
 The AB bond is largely covalent with a δ+ on A.
 The compound is largely ionic with A as the cation.
 The AB bond is largely covalent with a δ- on A.

3. Which is the longest bond?

Question options:

 N-N
 N≡N
 All three bond lengths should be about the same.
 N=N




4. Estimate the heat of combustion for one mole of acetylene:

, CHEM133
Final Exam Study Questions
Lessons 4-7


C2H2(g) + O2(g) → 2CO2(g) + H2O(g)

Bond Bond Energy (kJ/mol)

C≡C 839

C–H 413

O=O 495

C=O 799

O–H 467

Question options:

 -1228 kJ
 -447 kJ
 365 kJ
 1228 kJ
 447 kJ

5. Which of the following groups contains no ionic compounds?

Question options:

 NaH, CaF2, NaNH2
 HCN, NO2, Ca(NO3)2
 PCl5, LiBr, Zn(OH)2
 CH2O, H2S, NH3
 KOH, CCl4, SF4

6. In which case is the bond polarity incorrect?

Question options:

 δ+Si–Sδ–
 δ+H–Fδ–
 δ+Mg–Hδ–
 δ+Cl–Iδ–
 δ+K–Oδ–
 7. The electron pair in a C-F bond could be considered

Question options:

 closer to C because carbon has a lower electronegativity than fluorine

, CHEM133
Final Exam Study Questions
Lessons 4-7


 closer to C because carbon has a larger radius and thus exerts greater
control over the shared electron pair
 centrally located directly between the C and F
 an inadequate model since the bond is ionic
 closer to F because fluorine has a higher electronegativity than
carbon

8. Which of the following bonds would be the most polar without being
considered ionic?

Question options:

 N-O
 C-O
 O-O
 Si-O
 Mg-O

9. Which one of the following is most likely to be a covalent compound?

Question options:

 CaO
 Sr(NO3)2
 NF3
 CsOH
 LiF

10. Which bond has the highest bond dissociation energy?

Question options:

All three bonds should have about the same dissociation energy.

 N=N
 N≡N
 N-N

11. Calculate the lattice energy of NaBr(s), given the following
thermochemical equations, where ΔIE and ΔEA are ionization energy and
electron affinity, respectively.

Na(s) → Na(g) ΔHf° = +107 kJ