Ch. 5, 19, 8.9, 11.4  thermodynamics  test  [100 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. Additional HW problem; thermo 2001  [20 points]

2 NO  +  O2  →  2 NO2                  ΔH = -114.1 kJ ;  ΔS = - 146.5 J / K

a. Calculate thequantity of heat released when 73.1 g of NO is converted to NO2

b. Use the data in the table below to calculate the value of the standard molar entropy, Sº, for O2 at 25 ºC

 

Sº (J / (mol K)

NO

210.8

NO2

240.1

2. Use the data in the table below to calculate the bond energy in kJ / mol of the nitrogen-oxygen bond in NO2.  Assume that the bonds in the O2 molecule are equivalent (i.e. They have the same energy).

 

Bond energy (kJ / mol)

Nitrogen-oxygen bond in NO

60

Oxygen-oxygen bond in O2

495

3. Is diamond stable ?  Justify your response using thermodynamics.  [10 points]

4. Estimate the boiling point of carbon tetrachloride using thermodynamics.  [10 points]

5. A 65.0 g copper cylinder was in a 275 mL water bath at 95.0 ºC for 15 minutes.  This piece of copper was quickly transferred to 125.0 g of water at 21.0 ºC.  What would be the highest temperature of the water ?   Copper’s specific heat = 0.39 kJ / (kg K).  [10 points]

6. In regards to dissolving solid sodium chloride versus solid sodium hydroxide in water, [10 points]

a. is ΔS > 0 ?  or ΔS < 0 ?  justify your answer.

b. rationalize the relative values of ΔS for (i) solid → aqueous and (ii)  formation of hydration shells.

7. In the following reactions, is ΔS > 0 ?  ΔS < 0 ?  ΔS  ≈ 0 ? ambiguous ?  justify your response without any calculations.  [15 points]

a. Synthesis of gaseous ammonia from gaseous hydrogen and gaseous nitrogen.

b. Melting ice

c. Mixing aqueous solutions of calcium nitrate and sodium phosphate

8. Old topic:  [25 points]

a. Describe / rationalize the hydrogen emission spectrum

b. Sketch the PES (photoelectron spectrum) for the nitrogen atom; label both axis and the peaks in the spectrum; include appropriate relative values on both axis.

c. What is the orbital diagram of nitrogen ?