Spring 2001                             CHE 431/ENS 447               Name________________

Sample Test #1

Ch 1-3; Baird

 

Useful information

 

E = hn              PV=nRT          Vs_phere = 4/3 pr³                      A_sphere = 4pr² 

1 atm = 2 x 10¹⁸ molecules/cm³

 

Show all work on problems and give units for each numerical answer.

 

Part One:  Fill in the Blank/Multiple choice (3 points each).

 

1.                  Tropospheric ozone formation is favored when

 

I    [O₂] is low                        III  [NO] is high

II  [NO] is low                        IV  [NO₂] is high

 

(a)   I and II

(b)   I and III

(c)   II and III

(d)   II and IV

(e)   I, II, and IV

(f)     all

(g)   none

 

2.                  Calculate the energy of a photon of infrared light with l = 1000 nm.

 

(a)   3.3 x10^-43 J/photo

(b)   2 x10^-19 J/photon

(c)   1 x10⁵ J/photon

(d)   2 x10^-37 J/photon n

(e)   1 x10^-5 J/photon

 

3.                  The concentration of CO in the atmosphere is approximately 0.2 ppm.  What is the concentration in molecules/cm³?

 

^(a)       4 x10¹¹ molecules/cm³

(b)   4 x10¹⁷ molecules/cm³

(c)   1 x10^-25 molecules/cm³

(d)   1 x10¹⁷ molecules/cm³

(e)   2.4 x10⁴¹ molecules/cm³

 

4.                  A __________ pollutant is one that is formed by reactions in the atmosphere.

 

5.                  The _________ region of the atmosphere extends from 50-90 km above the surface of the earth.

 

6.                  Which molecules serve as “chlorine reservoirs” in the Antarctic winter?

 

I    Cl₂                        III  CF₂Cl₂

II  HOCl            IV  ClONO₂

 

(a)   I and II

(b)   I and III

(c)   I and IV

(d)   II and IV

(e)   I, II, and IV

(f)     all

(g)   none

 

Part Two:  Problems

 

If you can’t answer a part, guess and use your guess in the next part!!!

 

7.                  The amount of CH₄ emitted annually is estimated to be 25 to 50 times greater than the amount of N₂O emitted annually, yet the atmospheric concentration of CH₄ is estimate to be only 6 times higher.  Explain.

 

8.                  Choose one of these air pollutants, CO, NOx, VOCs, and particulates.  Give examples of the following information.

(a)   environmental effects

(b)   human health effects

(c)   major sources

(d)   atmospheric reactions

 

9.                  Consider the following reaction:

 

OH + O₃ à HO₂ + O₂

DH = -159 kJ/mol

E_a = 7 kJ/mol

 

(a)   Draw a reaction coordinate diagram.

(b)   Is the reaction favored or unfavored?

(c)   Will the reaction occur rapidly at room temperature?

(d)   What factors will increase the rate of reaction?

 

10.              Describe the accepted mechanism for the destruction of ozone in the lower stratosphere catalyzed by Cl.  Discuss two methods scientists used to prove the mechanism.

 

Answer key