Gas, nuclear chem., & kinetics  test      [100 points]                         AP Chemistry

For problems involving calculations, show your work in an organized manner, include any relevant equation (or formula and conversion factor(s)), put the proper units in your calculations / answer, and 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.   ideal versus real gas.   [10 points]

a.  What are the properties of an ideal gas ?

b.  the van deer Waals equation describes the behavior of a real gas. 

i.)  write the van deer Waals equation

ii)  What does the various parameters in this equation reflect ?

2.   A 35 mL container at 20 °C has a pressure of 750 torr.  The container was immersed in a 55 °C water bath and its pressure changed to 75 kPa; what is the volume of the container ?  [10 points]

3.  A rigid 10.0 L container filled with oxygen gas has a pressure of 32.0 atm at 25 °C.  A spark in the container causes some of the oxygen to become ozone (the reaction is:  3 O2 (g)   -->  2 O3 (g) ); the pressure in the container drops to 30.369 atm at 25 °C.  What is the partial pressure of ozone ?  [10 points]

4.  write the equation describing the (hypothetical ?) nuclear reaction involving   __.  [15 points]

a.  alpha decay of  mercury - 210:  _______________________________

b.  positron emission of phosphorus - 35:  __________________________

c.  fill-in the blank:  uranium - 238  -->  2 neutrons  +  lanthanum – 142   +  _________

d.  what type of nuclear reaction is shown in part c ?  ________________

e.  what type of nuclear reaction is 17N  --> 17O:  ________________


5.   A 5.0 mCi sample has a billion radioactive isotopes, where Ci = 3.7 * 1010 isotopes disintegrating per second.   What is the half-life of the isotope ?  [10 points]

6.  find the rate law (include the value & units of the rate constant) for the reaction:  N2   +  H2   -->  NH3 ;  based on the following hypothetical experimental data.      [15 points]

Expt

[N2 ]  (M)

[H2 ]  (M)

2

1

1.0

1.0

5.0

2

1.0

4.0

10.0

3

2.0

9.0

30.0


7.  If the activation energy of the forward reaction is 55 kJ / mole for  O2 (g)   +  H2 (g)   -->  H2 O2 (g) ,  what is the activation energy of the backward reaction ?  [10 points]

8.   For the reaction mechanism:    [10 points]

NO2   +  F2   -->  NO2 F  +  F    [slow]
NO2   +  F    -->  NO2 F

a.  what is the reaction corresponding to this reaction ?

b.  identify all intermediate(s) and catalyst(s) in this mechanism

c.  what is the rate law based on this mechanism ?

9.  For the reaction, O2 -->  O3 , using graphical analysis, how to differentiate between a 0th, 1st, and 2nd order reaction and determine its rate constant.  [10 points] 

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Gas, nuclear chem., & kinetics  retest               [100 points]                         AP Chemistry

For problems involving calculations, show your work in an organized manner, include any relevant equation (or formula and conversion factor(s)), put the proper units in your calculations / answer, and have the proper number of significant figures in your answer. 

 

1.  A container of 1.0 L of helium and 2.0 L of methane has the same temperature and number of moles of gas.  What is the relative __ between these 2 gases ?  rationalize / justify your answer.  [15 points]

a.   average velocity of the gas

b.  “a”  term in the van deer Waals equation

c.  “b” term in the van deer Waals equation

 

2.  At 20 °C, the vapor pressure of (pure) benzene (C6 H6 ) and (pure) toluene (C6 H5 CH3 ) is 75 torr and 22 torr, respectively.  What is the mole fraction of benzene in the  gas phase above a liquid solution containing 3.0 moles of toluene and 1.0 mole of benzene ?  [hint:  Raoult’s law;  15 points]

3.  It takes 25 hours for a (hypothetical ?) radioactive isotope to decay from 75 mCi to 25 mCi (Ci = 3.7 * 1010 disintegrations / second).  What is the half-life of this isotope ?  [10 points]

4.  3H has a half-life of 12.3 years.  A radioactive sample originally contains 35 mg 3 H, and currently has 7.0 mg 3 H; what is the “age” of the sample ?  [10 points]

5.   For the reaction mechanism   [10 points]

                Rx mechanism 

a.  what is the reaction corresponding to this mechanism ?

b. identify any intermediates in the mechanism.

c.  what is the rate law based on this mechanism  ? 


6.  If doubling the temperature from 25.0 °C to 50.0 °C, doubles the rate of a reaction, what is the activation energy of such a reaction ?  [10 points]

 

7.   Catalyst.  [10 points]

a.  sketch the reaction energy profile for a catalyzed versus uncatalyzed reaction; label both axis & identify the catalyzed versus uncatalyzed plot.  

b.  what is the effect of a catalyst on the rate of a chemical reaction and its basis.

 

8.  old topic:  pick one question; clearly identify your choice; if you do both problem then your score would be the  lowest score.   [20 points]

a.  5.0 g solid sodium nitrate was added to 45 mL of water at 21 °C; what is the temperature after all of the sodium nitrate was dissolved in the water ? 

b.  Experimental design:  briefly describe an experimental method to  __  and include ALL experimental measurements  (not subsequent calculations).  

i.  determine ΔH to dissolve 1.0 gram of solid lithium chloride in 35 mL of water.

ii.  determine the [Pb2+ ] in a 75 mL aqueous solution of Pb(NO3 )2