"How many CuFt of CO2 are produced when you burn 1 barrel of crude
oil?" Assume STP and a "standard" chemical makeup of medium weight
crude (if such a thing is possible!)

1 barrel of crude oil contains about 5.8 x 10^6 BTU of energy if
conbusted completely (see
http://www-personal.umich.edu/~rcnh/gs102/EnergyEquiv.html).  This is
only an approximate number, as the composition of crude oil varies
from locality to locality.

Every BTU of energy produced releases 0.0202 grams of carbon (see
http://www.eia.doe.gov/oiaf/1605/gg99rpt/tblb4.html), or (adding the
mass of the oxygens in each molecule of CO2), 0.0741 grams of CO2.

0.0741 grams CO2/BTU * 5.8 * 10^6 BTU/barrel = 4.297 * 10^5 grams
CO2/barrel.

The molecular weight of CO2 is 44.0 grams/mole.  

One mole of a gas (assuming an ideal gas) at 1 standard temperature
and pressure occpies ~22.4 liters = 0.791 ft^3, so:

[4.297*10^5 grams CO2/barrel]/[44.0 grams CO2/mole CO2]*[0.791 ft^3
CO2/mole CO2] = 7725 ft^3 CO2/barrel