Arkansas State University 
Department of Chemistry
and Physics
CHEM2004
Exam 2

CHEM2004                                                                 Name_________________________

Exam 2                                                                         Fall 2009

 

1.         Fill in the blank with the element that bests matches (15 points)

 

Group VIIA diatomic liquid _____________________
Most abundant noble gas on earth _____________________
Most reactive noble gas    _____________________
Used for making phosphoric acid       _____________________
Blue black solid       _____________________
Used in car batteries _____________________
Pyrophoric  _____________________
Colorless diatomic gas  _____________________
Neon lights    _____________________
Inert gas used in metallurgy _____________________
Used to decolorize glass  _____________________
Metallic liquid at room temperature _____________________
Most reactive metal _____________________
Cryogen  _____________________
Most reactive nonmetal _____________________

   

2.         Write the prepared for bonding configuration for each element below and tell the number of bonds expected for each:    (9 points)

 

                        prepared for bonding                       number of bonds

 

a)  S

 

 

b)  B

 

 

c)  Si

 

3.         Match the allotrope with the best structure description:            (20 points)

 

_____ Gray tin   a.         ring structures
_____ White phosphorus   b.         helical chains
_____ Black phosphorus  c.         puckered sheets
_____ Tellurium  d.         planar sheets
_____ Stable form of antimony   e.         linear chains
_____ Red selenium  f.          metallic lattice
_____ Silicon   g.         tetrahedrons
_____ Boron  i.          icosahedrals
_____ White tin k.         diamond structure
_____ Germanium  

    

4.         Sulfur melts at 119 oC.  When you heat S above 160 oC it creates long chains.  Further heating gives S2 and S3. Describe the color of each of these species.  (8 points)

 

  Sulfur  ______________________
     
  Long sulfur chains ______________________
     
  S2   ______________________
     
  S3   ______________________

                                  

5.         Match the property with the allotrope.      (10 points)

 

_____ layered sheets    A. graphite
_____ sp2 hybridized    
_____ nanotubes  B. diamond
_____ most dense  
_____ flakes off easily C. bucky balls
_____ has fused rings  
_____ discovered in the mid-1980’s  
_____ sp3 hybridized  

      

6.         The element Benjaminium (Bn) has 3 allotropes.  Allotrope A has 5 single bonds, allotrope B has 1 single bond and 2 double bonds, and allotrope C has 1 double bond and 1 triple bond.  If the sigma bond energy is 200 kJ/ mol and the pi bond energy is 100 kJ/ mol, which allotrope is favored?  (show work)  (15 points)

 

7.         Circle the correct answer for each of the following questions.

(6 points)

 

a)  The element with the highest ΔH(atomization):   C  or Si

 

b)  The element with the highest ΔH(atomization):   Se  or Br

 

c)  The element with the highest ΔH(atomization):   Cr or Mo

 

8.         Explain using drawings and M.O. theory, why metals are conductors and nonmetals are insulators.  Label all parts.  How many bonding M.O.'s do you expect for 1 mole of Cu atoms?  (10 points)

 

9.         Choose any 4 of the following and draw the structure.  DO NOT answer more than four – this will result in a zero for the question.   (8 points)

 

 

a)  Se8+2                                                                      e)  As73-

  

b)  Te6+4                                                                      f)  P4

 

c)  Pb52-                                                                      g)  BN17

 

d)  Sn94-                                                                      h)  S8