Quiz Four Practice, Chemistry 111, Lycoming College, Feb. 16, 2005, Dr. Mahler
Fair Game for Friday’s Quiz: All previous material (Ch. 11, 12, 13). New Material – Ch. 13 section 9, Chapter 14 Sections 1, 2 and 3. Relevant Homework: Ch. 13 all assigned, but especially 61, 65, 67, 68 and 85c (all mechanisms); Ch. 14 problems 22, 25, 29, 32, 35, 38 and 41 (keys on web: http://www.lycoming.edu/chem/spring2005/111/keys.htm)
1) Possible essay / short answer type questions:
2) A reaction was believed to occur by the following mechanism:
Step 1) A2 à A + A and its reverse, A + A à A2
Step 2) A + A + B à A2B
Step 3) A2B + C à A2C + B
a) Write the overall reaction. b) Write the rate law for each step and indicate its molecularity. c) Identify each species as a reactant, product, intermediate, or catalyst.
3) The following mechanism has been proposed for the reaction of chlorine and chloroform, CHCl3:
Step 1) Cl2 à Cl + Cl and its reverse, Cl + Cl à Cl2 (both fast)
Step 2) CHCl3 + Cl à CCl3 + HCl (slow)
Step 3) CCl3 + Cl à CCl4 (fast)
Write the rate law based on this mechanism, clearly stating any assumptions / reasoning.
4) Write the expression for Kc for each of the following reactions:
a) NH4HS (s) ó NH3 (g) + H2S (g)
b) ZnO (s) + CO (g) ó Zn (s) + CO2 (g)
c) SbCl5 (g) ó SbCl3 (g) + Cl2 (g)
d) H2 (g) + I2 (g) ó 2 HI (g)
5) Calculate the following (all at equilibrium):
a) The concentration of H2 (g) in reaction 4d), above, if at 500 K, Kc = 160, [HI] = 2.21 mmol/L, and [I2] = 1.46 mmol/L.
b) At 500 K, Kc = 3.5 x 10-4, [SbCl5] = 0.15 M, [SbCl3] = 0.20 M. What is [Cl2]? See 4c).