Chapter 8 Practice Exam

Practice Exam Chapter 8
I have put the questions we may not get to for this exam at the end of the practice exam)
1. How many lone pairs of electrons are assigned to the sulfur atom in H2S?
a) 0

b) 1

c) 2

d) 3

e) 4

2. Which of the following is a correct Lewis structure for nitrous acid, HNO2?

3. The central atom in PH3 is surrounded by
a) three single bonds and no lone pairs of electrons.
b) three single bonds and one lone pair of electrons.
c) three single bonds and two lone pairs of electrons.
d) two single bonds, one double bond, and no lone pairs of electrons.
e) two single bonds, one double bond, and one lone pair of electrons.
4. One resonance structure for OCN- ion is drawn below. What is the formal charge on each atom?

a) O atom = 0, C atom = 0, and N atom = 0
b) O atom = 0, C atom = 0, and N atom = -1
c) O atom = -1, C atom = 0, and N atom = 0
d) O atom = -1, C atom = -1, and N atom = +1
e) O atom = +1, C atom = 0, and N atom = -2

5. Which of the following are resonance structures for nitrite ion, NO2-?

a) 1 and 2

b) 2 and 4

c) 3 and 4

d) 1, 2, and 3

e) 2, 3, and 4

6. . Which of the following elements is able to form a molecular structure that exceeds the octet rule?
a) Ne

b) B

c) O

d) F

e) I

7. Which of the following elements is most likely to form a molecular structure that disobeys the octet rule? a) B

b) C

c) N

d) O

8. What is the correct Lewis structure for IF3?

9. The central atom in PF5 is surrounded by
a) five single bonds and no lone pairs of electrons.
b) five single bonds and one lone pair of electrons.
c) four single bonds, one double bond, and no lone pairs of electrons.
d) four single bonds, one double bond, and one lone pair of electrons.
e) three single bonds, two double bonds, and no lone pairs of electrons.

e) F

10. Which of the following species will have a Lewis structure most like that of ICl4+?
b) SO42-

a) XeF4

c) PF4+

e) IO4-

d) SF4

11. Which of the following compounds has polar covalent bonds: NaBr, Br2, HBr, and CBr4?
a) NaBr only
b) Br2 only
c) HBr only
d) Br2 and HBr
e) HBr and CBr4
12. Use Lewis structures to predict the bond order for a carbon-oxygen bond in carbonate ion, CO32-.
a) 1/2

b) 1

c) 4/3

d) 3/2

e) 2

13. In benzene, C6H6, the six carbon atoms are arranged in a ring. Two equivalent Lewis structures can be drawn for benzene. In both structures, the carbon atoms have a trigonal planar geometry. These two equivalent structures are referred to as ________ structures.

14.

Choose which central atom in the following molecules is most electronegative.
a) PH3

b) CH4

c) H2S

d) H2O

e) NH3

15. Predict which of the following compounds has covalent bond(s) that are the most polar.
a) HF

b) CI4

c) H2S

d) NBr3

e) HI

16. Given the following electronegativity information arrange the following bonds from most to least polar. C–O

C-C

H-F

Electronegativity values C = 2.5

O = 3.5

H=2.1

a) C–O > C-C > H-F
c) C-C > C-O > H-F
e) H-F > C-O > C-C

b) C-C > H-F > C-O
d) H-F > C-C > C-O

F = 4.0

17. Which combination of atoms is most likely to produce a compound with ionic bonds?
a) B and Cl

b) S and H

c) C and N

d) Si and I

e) Al and Br

18. Which of the following statements is/are CORRECT?
1. Ionic bonds form when one or more valence electrons are transferred from one atom to another. 2. Covalent bonds involve sharing of electrons between atoms.
3. In most covalently bonded compounds, electrons are shared equally between the atoms.
a) 1 only
b) 2 only
c) 3 only
d) 1 and 2
e) 1, 2, and 3

19. A selenium atom has ________ valence electrons.
a) 2

b) 6

c) 16

d) 28

e) 34

20. How many lone pairs of electrons are assigned to the carbon atom in carbon monoxide?
a) 0

b) 1

c) 2

d) 3

e) 4

21. How many electrons should be placed in the lewis dot structure of SCN- ________.
22. When heated, azomethane decomposes into nitrogen gas and ethane gas.
CH3N=NCH3(g) → N2(g) + C2H6(g)

Bond

Bond Enthalpy
(kJ/mol·rxn)

Bond

Bond Enthalpy
(kJ/mol·rxn)

C-H

413

N-N

163

C-N

305

N=N

418

C-C

346

NN

945

Using average bond energies, calculate the enthalpy of reaction.
a) -611 kJ

b) -527 kJ

c) -429 kJ

d) -313 kJ

e) -263 kJ

1. c

2. d

3. b

4. b

11. e

5. a

6. e

7. a

8. e

9. a

10. d

is the correct answer

NaBr is ionic. CBr4 is nopolar but it has polar covalent bonds as does HBr
12. c
19. b

13. resonance
20. b

14. d

15. a
21. 16

16. e
22. e

17. e

18. d