Arkansas State University 
Department of Chemistry
and Physics
CHEM1013
Exam 3a
(Note: only the questions are listed, spaces have been removed for brevity)

SHOW WORK ON ALL PROBLEMS

1. Define each of the follwoing as either an open, closed or isolated system.    (6 points)

 a) An unopened egg warming on the counter ________________

 b) A warm cup of coffee cooling on the table ________________

 c) A closed thermos of hot chicken noodle soup _________________

2. Define Hess’ Law.      (5 pts)

3. Using the table provided, calculate the heat of reaction for:       (10 points)

 2 C2H2 (g)  +   5 O2 (g)  -------->  4 CO2 (g)  +   2 H2O  (l)






4. Given the following reactions, calculate the enthalpy change for the formation of C2H6 from its elements.  (15 points)

C(graphite)  +  O2 (g) --------->  CO2 (g)        DH = -393.5 kJ

 H2 (g)   +  1/2 O2 (g) --------->  H2O (l)      DH = -285.8 kJ

 2 C2H6 (g)  +  7 O2 (g) -------->  4 CO2 (g) + 6 H2O (l)DH = -3119.6 kJ
___________________________________________________________________

  2 C(graphite)  +  3 H2 (g) ----->  C2H6 (g)