CHEM 121 &= nbsp; &nbs= p; Sample Exam #3

1.	Carbon uses ______ hybrid orbitals in ClCN. = ;
A.	sp

sp²

sp³

sp³d

sp³d²

Valence bond theory pred= icts that iodine will use _____ hybrid orbitals in ICl₂^-= .

sp²

sp³

sp³d

sp³d²

E.	none of these choices is correct

3.	(4 pts) A molecule with the form= ula AX₄ uses _________ to form its bonds.

A.	sp hybrid orbitals

B.	sp² hybrid o= rbitals

C.	sp³ hybrid o= rbitals

D.	sp³d hybrid orbitals

sp³d² hybrid o= rbitals

Which one of the followi= ng statements about orbital hybridization is incorrect?

A.	The carbon atom in CH₄ is sp³ hybridized.

B.	The carbon atom in CO₂ is sp hybridized.<= /p>

C.	The nitrogen atom in NH₃ is sp² hybridized.=

D.	sp² hybrid o= rbitals are coplanar, and at 120° to each other.

E.	sp hybrid orbitals lie at 180° to each other.

5.	(4 pts) A molecule with the formula AX₃E uses _________ to form its bonds.

A.	s and p atomic orbitals

B.	sp³ hybrid o= rbitals

C.	sp² hybrid o= rbitals

D.	sp hybrid orbitals

E.	sp³d² hybrid o= rbitals

6.	According to valence bond theory, the triple bond in ethyne (acetylene, C₂H₂) consists of =

A.	three σ bonds and no π bonds.

B.	two σ bonds and one π bond.

C.	one σ bond and two π bonds.

D.	no σ bonds and three π bonds.

E.	none of these choices is correct
7.	Which of the following statements relating to molecular orbital (MO) theory is incorrect?=

A.	Combination of two atomic orbitals produces one bonding and one antibonding MO.<= /o:p>

B.	A bonding MO is lower in energy than the two atomic orbitals from which it = is formed.

C.	Combination of two 2p orbitals may result in either σ or π MOs.=

D.	A species with a bond order of zero will not be stable.

In a stable molecule having an even number of electrons, all electrons must be paired.

In the context of molecu= lar orbital (MO) theory, explain how atomic p orbitals can give rise t= o:
a. a σ MO
b. a π MO

9. = Using the MO energy levels shown on page 414 of your test, provide a MO orbital energy diagram for the N₂^1- ion. Would you expect this ion to be stable? What is the bond order between the two nitrogens?

10. Identify the pr= incipal interparticle force in each of the following compounds:

&nbs= p; (a) HOCH₂CH_2OH

&nbs= p; (b) CH₃F

&nbs= p; (c) NH(CH₃)₂

&nbs= p; (d) CH₃CH₂= CH₂ CH₂CH₃

_{=
; <=
/span>}(e) LiF

11.	Examine the phase diagra= m for the substance Bogusium (Bo) and select the correct statement.

A.	Bo(s) has a lower density than Bo(l).

B.	The triple point for Bo is at a higher temperature than the melting point for= Bo.

C.	Bo changes from a solid to a liquid as one follows the line from C to D.

D.	Bo changes from a liquid to a gas as one follows the line from C to D.<= /o:p>

E.	Point B represents the critical temperature and pressure for Bo.

12.

4.	In which of the following compounds will the molecules not form hydrogen bonds with each other?