Chemistry 65.100 A, V
Midterm Test #2
November 7, 1997
A periodic table is on the back of this sheet!
Part A. Answer each question with a few sentences or equations where necessary. (5 Marks each)
1. What kind of hybrid orbitals does phosphorus use in forming PCl5?
2. What is meant by the term "standard state"?
3. What is a disproportionation reaction?
4. What is Hess’ law?
5. Draw a molecule of HBr and clearly show the direction of the dipole moment.
6. The bond order of a particular spedcies increases when the species is positively ionized. What can you say about the molecular orbital of the electron removed?
7. Reaction A has DH = -100 kJ mol-1. Reaction B has DH = -200 kJ mol-1. From this information alone, what can we say about the rates of these two reactions?
8. Which of Li(s) and Zn(s) would you expect to be a stronger reducing agent? Why?
Part B. Answer each question. (15 marks each)
1. Using VSEPR theory, predict the shapes of the following species. Note that I am looking for the shape of the species as opposed to the shape of the charge clouds about the central atom.
(a) SbF5 (b) SeO3-2 (c) SeCl4
2. Balance the following REDOX reaction in basic solution: Cl2(g) à Cl-(aq) + ClO-(aq)
3. Calculate DH (in kJ) for the reaction:
3 C(s) + 4 H2(g) à C3H8(g)
given the following data:
C3H8(g) + 5 O2(g) à 3 CO2(g) + 4 H2O(l) DH = -2220 kJ
C(s) + O2(g) à CO2(g) DH = -394 kJ
H2(g) + ½ O2(g) à H2O(l) DH = -286 kJ