General Chemistry II
11 March 2015
Oxyhydrogen Gas Oxyhydrogen is a gas mixture created by the electrolysis of water. It is easy to produce and has an efficiency of about 83%. There are many uses for this mixture, one is as a fuel for combustion engines. Oxyhydrogen is a clean fuel that was originally called brown’s gas. Stanley Meyer said that cars could be run on water; he called his technology a fuel cell. Oxyhydrogen was the fuel he wanted to use. Oxyhydrogen gas is created through the breakdown of water into Hydrogen and Oxygen gas in a process known as electrolysis. The equation for this reaction is 2H2O(l) → 2H2(g) + O2(g). This endothermic reaction requires 285.83 kJ of energy per mole of water at 298K. Beware our equation is for two moles of water and would require double the amount of activation energy. The process of electrolysis passes an electric current from a negatively charged cathode to a positively charged anode and as the charge travels through the water electrons are excited and break the H-O bonds. During the process of electrolysis hydrogen gathers around the negatively charged cathode and oxygen collects around the positively charged anode. These gases begin to rise because they are less dense then liquid H2O molecules. These gases can be collected and stored for later use. There are many risks when dealing with hydrogen. It is flammable in mixtures where it is 4% to 94% concentration of any gas mixture by volume. This means when hydrogen is greater than 4% of a gases concentration it is in danger of a combustion reaction. The adiabatic flame temperature of hydrogen combustion can reach temperatures of 2800 oC according to the Journal of Mechanical Engineering Research. For comparison octane’s adiabatic flame temperature is around 1950 oC. The adiabatic temperatures are the temperatures that can be reached during a combustion reaction. Making hydrogen a lot more dangerous than octane. There are many benefits to Oxyhydrogen. One benefit is that Oxyhydrogen is a clean fuel. The only byproduct from burning oxyhydrogen is water in the form of water vapor. This means no detriment to society in general. Here is the equation for combustion 2H2(g) + O2(g) → 2H2O(g). There is no need for catalytic converters because even if some of the fuel escapes through the engine it’s less dense than our common air and will dissipate quickly. This density also makes it difficult to capture and store. We can use renewable sources to generate the energy needed to break the bonds and create the fuel. Systems can be designed and run on low voltage with high amperage to produce large amounts of gas quickly. The system needs electrolytes to make it efficient. A commonly used electrolyte is sodium hydroxide (NaOH) because it dissolves into Na+ and OH- ions easily in water. These ions allow the electrical current to flow and break the H-O bonds. There is no need for additional amounts of an electrolyte to be added after the systems initial amount because the electrolyte never leaves the system. This process is roughly 83% efficient. The efficiency is determined by the potential energy of the products after the reaction and dividing it by the energy required to separate the bonds. The equation for the Gibbs free energy exchange of hydrogen combustion is:
ΔG = ΔH - TΔS = -285.83 kJ + 48.7 kJ = -237.1 kJ.