CH301H - Principles of Chemistry I: Honors
Fall 2011, Unique 51040


Homework, Week 4

Homework, week 4
Answer key

1.  The bond lengths of the X-H bonds in NH3, PH3, and SbH3 are 1.02, 1.42, and 1.71 Å, respectively.  Estimate the length of the As-H bond in AsH3.  Which of these four hydrides has the weakest X-H bond?

2.  The bond lenth of F2 is 1.417 Å, not twice the atomic radius of F, which is known to be 0.61 Å.  What can account for the unexpected length of the F-F bond?

3.  Estimate the percent ionic character of the bond in each of the following diatomic molecules, based on the information given.

               Bond length (Å)    Dipole moment (D)
     ClO    1.573                      1.239
     KI       3.051                      10.82
     TlCl    2.488                      4.543
     InCl    2.404                      3.79

4.  For each of the following molecules, draw and name the appropriate molecular geometry.  Describe distortions from that geometry caused by the presence of lone pairs.  In each case, the central atom is listed first and the other atoms are directly bonded to it.

     a)  ICl4-
     b)  OF2
     c)  BrO3-
     d)  CS2
     e)  CHO2-

5.  Predict the structure of NNO.  This molecule has a small molecular dipole moment.  Predict the direction of the dipole moment vector, keeping in mind that it is defined as pointing from the negative end of the molecule to the positive end of the molecule.

6.  In words, and using any information in your textbook you wish, describe a general relationship between bond lengths and bond energies in similar molecules.

7.  Draw the preferred lone pair placement for octahedral geometries containing up to three lone pairs.  

8.  The element xenon is by no means chemically inert.  It forms a number of stable compounds with electronegative elements such as fluorine and oxygen.  These compounds can in turn react with water to form every more complex compounds.  Predict the structures of the following compounds:  XeF2, XeF4, XeO4, H4XeO6, and XeOF4.