[ 57 ] Earth and Space Science GED ® TEST SCIENCE FLASH REVIEW • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Natural gas, petroleum, and coal are fossil fuels. Ethanol is derived from biomass. Information about five different fuel sources is listed in the following table. Energy Content (kJ/g) CO Released (mol/10 3 kJ) 2 Hydrogen 120 0 Natural gas 51.6 1.2 Petroleum 43.6 1.6 Coal 39.3 2.0 Ethanol 27.3 1.6 Based on the data in the table, what is the best estimate of the energy content of fossil fuels? A. 40 kJ/g B. 42 kJ/g C. 45 kJ/g D. 50 kJ/g