Chapter Twenty-one:
Chemical Processes Based on Sulfur, Phosphorus, and Nitrogen

1.  Propose several ways in which predictions from Le Chatelier's principle could be used to improve the yield of SO3(g) from SO2(g) and air.
There are a couple of ways in which we can shift the equilibrium of the production of SO3(g) from SO2(g) and air.  One way is to increase the pressure.  In observing the chemical equation
SO2  +  1/2 O2 ---->  SO3
we notice that the number of mole of gas molecules decreases as SO3 is produced.  Since the there are more moles on the left side of the equation, then by increasing the pressure during the reaction would increase the rate of reaction.  The number of mole on the left side would react more to counteract the stress put on the system.  Another way to improve the yield would be to carry out the reaction under low temperatures.  The reaction is exothermic, so therefore running the reaction in low temperatures would increase the yield.  The rate of reaction would be slowed down by this process though, so an equilibrium must be found.

9.  Hot concentrated sulfuric acid reacts with phosphorus to give sulfur dioxide, phosphoric acid, and water.  Write a balanced chemical equation for this reaction.
5H2SO4  +  2P  ----->  5SO2  +  2H3PO4  +  2H2O

14.  Observations of lightning suggest that the average lightning stroke produces 1027 molecules of NO.  The rate of lightning strokes worldwide is about 100 per second.  According to these data, how much nitrogen (in metric tons)  is fixed annually by lightning strokes?
We know that 1027  molecules of NO are produced in one lightning stroke and there are 6000 of these per minute, we concluded this by multiplying 60 seconds by 1 minute.  From there we can determine how many molecules are produced in a minute.

1.0 x 1027 molecules  x  6000  =   6.0 x 1030 molecules / min

We can determine the moles produced per second by dividing our current rate by Avogadro's number.

6.0 x 1030  /  6.02 x 1023  =  9.97 x 106 mole / min

From there we know that there are 60 minutes per hour, 24 hours per day, and 365 days per year.  We multiply our rate per second by each of these terms to determine how many are produced per year.

9.96 x 106 mole/min  x  60  x  24  x  365  =  5.24 x 1012 mol / yr

We then can determine the grams produced by multiplying our rate by the gram formula weight of NO, 30 grams/ mol.

5.24 x 1012 mol/yr  /  30 g/mol  =  1.57  x 1014 g/yr
=  1.57  x 108 metric tons / yr

23.  trans-Tetrazene has a formula N4H4.  It consists of a chain of four nitrogen atoms with the two terminal nitrogen atoms bonded to two hydrogen atoms each.  Draw a Lewis diagram for this compound.
H                              H
\        ..       ..        /
:N---N===N---N:
/                           \
H                              H