Answer to Question #33526 in Organic Chemistry for Gowtham

Question

as we all know petrol consists of hydrocarbons i.e., carbon and hydrogen. water consits of hydrogen oxygen bonding. if we deoxygenate the water, it consists only of hydrogen. is there any methods to form bond between carbon and hydrogen artificially so that we can use CARBON ADDED DEOXYGENATED WATER as the fuel. please reply me soon...

Answer 1

It takes a net of 118 kcal to decompose 2 moles of H₂O into its elements. Actually it takes more than 118 kcal to decompose the water into its atoms, but some of the energy is given back as the atoms immediately bond together to form molecules of hydrogen and oxygen.
Let's look at the numbers.
The bond energy of the H-O bond is 110 kcal.
The bond energy of H-H bonds is 103 kcal.
The bond energy of the O=O bonds is 116 kcal.
The decomposition of 2 molecules of water requires breaking 4 H-O bonds and thus the input of 440 kcal.
The formation of 2 moles of hydrogen yields 206 kcal (2 x 103).
The formation of 1 mole of oxygen yields 116 kcal.
The difference between the energy released (206 + 116 = 322 kcal) and the energy consumed (4 x 110 = 440 kcal) gives the net energy consumed = 118 kcal.
The bond energy is essentially the average enthalpy change for a gas reaction to break all the similar bonds. For the methane molecule, CH₄, 435 kJ is required to break a single C-H bond for a mole of methane, but breaking all four C-H bonds for a mole requires 1662 kJ. Thus the average bond energy is (1662/4) 416 (not 436) kJ/mol.

If you’re going to make a hydrocarbon fuel, one of the things you have to do is remove oxygen from biomass. You can do it by using hydrogen, which is expensive and also decreases the energy efficiency of your process. So if there’s a way to remove the oxygen from the biomass chemically, then you’ve densified it significantly.