Name ______________________________ SS# _________________________ Section _________

Instructions: Put your name, social security number, and section number on the top of this exam page. Read the entire exam. Answer the following five (5) parts in the notation and conventions of the lecture for a total of 100 points. Work alone and consult no one, living or dead, about this test (except Brucat) until after you leave the room. Notebooks, textbooks and any other study material is not allowed in the exam room. You may use only your writing and calculating instruments; sharing of instruments during the exam is NOT allowed. Show work where appropriate and write only on this exam page. Show proper units to receive credit. Your name on this exam states the assertion: I hereby pledge that I have neither given nor received any unauthorized aid in relation to this exam

R = 0.08206 latm/molK = 8.314 J/Kmol Universal Gas Constant

Kb (water) = 0.512 K/m Kf (water) = 1.86 K/m

Part I Consider the kinetics of the elementary reaction 2A -> B. Initially the concentration of A, [A]0, is 2.7250 x 10-3 M and the initial concentration of B, [B]0 is zero. After 125 seconds, the concentration of B, [B], is found to be 1.1371 x 10-4 M.

What is the rate law for this reaction

Rate = k[A]2

What is the integrated rate law for this reaction?

1/[A] = 1/[A]0 + kt

What is the concentration of A, [A], at 125 seconds?

[A] = 2.498 x 10-3 M

What is the rate constant for this reaction?

k = 2.67 x 10-1 M-1 s-1



Part II A unimolecular decomposition of acetic acid dimer has a rate constant that approaches 1.15 x 1013 s-1 at infinite temperature. The activation barrier for this decomposition is thought to be 75.25 kJ/mol. What is the half life for decomposition of acetic acid dimer at room temperature (in seconds)?

t1/2 = 0.935 s

Part IIIa What is the normal boiling point of a 5.00 m solution of ethylene glycol, i.e.1,2-ethanediol, in water?

Tb = 375.71 K

Part IIIb The Osmotic pressure of a given system is found to be 0.0100 atm at 0.00 oC.. What is the osmotic pressure of the same system if the temperature is raised by 20.00 oC? All conditions but temperature are held constant.

p = 0.0107 atm

Part IV Consider the following reaction: A + B + C -> D. Initial rate as a function of initial concentration data for this reaction is compiled in the following table:
[A]0, M [B]0, M [C]0, M Initial rate, M/s
0.235 0.635 0.155 7.490
0.156 0.537 0.198 4.216
0.235 0.635 0.258 12.467
0.235 1.256 0.112 5.412

Show your Work:



The order of the reaction in A is 2

The order of the reaction in B is 0

The order of the reaction in C is 1

The rate constant for the reaction is 8.75 x 102 M-2 s-1



Part V Consider the net reaction H2 + 1/2 O2 H2O. Under certain circumstances this reaction explodes, as we saw in class. Explosions are runaway reactions that may have complex kinetics and mechanism.

a) Name or describe two distinct types of explosions

Thermal and Chain Branching

Write down a balanced initiation reaction in the explosion of H2 with O2

H2 + O2 = 2H + O2 (for example)

Write down a balanced propagation reaction in the explosion of H2 with O2

2H + O2 = 2OH (for example)

Write down a balanced termination reaction in the explosion of H2 with O2

H + O2 + M = H2O + M (for example)

PJ Brucat // University of Florida