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-   -   Difficult Chemistry Problem- ethanol and hydrogen powered SUV? (http://www.molecularstation.com/forum/chemistry-forum/26154-difficult-chemistry-problem-ethanol-hydrogen-powered-suv.html)

X_o 10-27-2008 07:20 AM

Difficult Chemistry Problem- ethanol and hydrogen powered SUV?
 
Ok there are two parts to this exercise. The first part is to compare the amount of ethanol (gallons) and hydrogen gas (liters) needed to drive a SUV that gets a reported fuel efficiency of 20.0 miles per gallon for gasoline (octane) over a distance of 300 miles.

The second part is to compute the number of square miles of corn that must be planted to produce ethanol that will be used to replace the amount of gasoline used in the US in the year 2007. The energy equivalent replacement.

This is what you will need to solve the two parts of the problem:

delta Hf (octane) = -250.1kJ/mole, delta Hf (ethanol) = -277.6kJ/mol, delta Hf (water) = -241.8kJ/mol, delta Hf (CO2) = -393.5kJ/mol

Densities of octane and ethanol are .691g/ml and .789g/ml respectively

The yield of ethanol are fermentation of corn is 2.5 gallons of ethanol per bushel of corn

The yield of corn in Nebraska, for example, was 235 bushels of corn per acre planted

The 2007 consumption of gasoline in the US was 1.42421076*10^11 gallons

The formula for octane is C8H18 and for ethanol is C2H5OH

To compute the volume (in L) of hydrogen gas, assume a pressure of 3000 psi and a temperature of 25 C

Equations needed for this problem is the combustion of octane, ethanol, and hydrogen

640 acres = 1 square mile


Please help me solve this devilish problem, ill forever be thankful.


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