Ch. 5, 19, 8.9, 11.4, 10   thermodynamics & gas                     test       80 points                      ap chemistry

Show your work in an organized manner, include (i) any relevant equation (or formula), (ii) conversion factor(s), (iii) put the proper units in your calculations and answer, and (iv) have the proper number of significant figures in your answer.

Academic Honesty:   The answers on this test are my own and I am using only the allowed set of notes as described in the syllabus.  I have not discussed the test questions with anyone before or during the test nor have I seen the test questions prior to the exam.  If you violate any of the preceding items or do not sign, your semester grade is a F.

                                                                                                Signature:  ___________________

1. Hydrogen gas effuses about 6.633 times faster than a hydrocarbon. The complete combustion of 1.00 g of the hydrocarbon generates 3.00 g CO2 and 1.227 g H2O.  What is the hydrocarbon’s chemical formula ?  [15 points]

2. The van deer Waals equation

van der waals eqn

  describes the behavior of a real gas.  [10 points]

a. What does the parameters, a and b, in the equation represent ?

b. What is the relative value of a and b for He versus Ar ?  justify your answer.

3. If a calorimeter’s heat capacity is 75.0 J / K and 35.0 mL of water at 75.0 ºC is added to 55.0 mL of water at 21.0 ºC, what would be the “final” (i.e. “plateau”) temperature ?  [10 points]

4. The combustion of ethane:  5.0 g C2H6(g)  +  10.0 g O2(g)  →   O2(g)  +  H2O(g) was used to heat 675 mL of water at 21.0 ºC; what is the “final” temperature of the water ?  [20 points]

6. What is ΔS in the below reactions:  positive ?  negative ?  zero ?  ambiguous ?  rationalize your answer without any calculations.  [15 points]

a. Melt ice

b. Dissolve solid sodium chloride in water

c. Mix aqueous solutions of silver nitrate and potassium chloride

d.  N2(g)  +  H2(g)  →  NH3(g)

e. Sublimation of dry ice

 7.  Estimate / calculate the boiling point of benzene, C6H6, using concepts in thermodynamics.  [10 points]