Hydrogen environment, endothermic reaction

A surplus of hydrogen and oxygen has to supply to the fuel cell to maintain the chemical potential between anode and cathode. The excess of hydrogen downstream of the fuel cell has to be converted due to safety reasons. It is not allowed to release unbumed compounds into the environment. The after burner in a fuel-cell heating appliances ensures that no unbumed substances will be released into the environmental. The heat of combustion of the after burner will be used in fuel-cell heating appliances to supply heat to endothermic reaction and/or supply heat to the heating system of the household. The after burner could be also used to heat up the fuel-cell system during start-up. 

Actually, if we could measure it, the temperature would rise ever so slightly as two hydrogen atoms combined to make a hydrogen molecule because 104 kcal/mol would be released as heat energy into the vessel. The environment in the vessel would warm up as the process proceeded. A reaction that liberates heat, one where the products are more stable than the starting materials, is called an exothermic reaction. The opposite situation, in which the products are less stable than the starting material, requires the application of heat and is called an endothermic reaction. 

This is an endothermic reaction in a hydrogen environment taking place in the vapor phase. The catalyst is the size of grains of rice and contains very costly platinum (which sells for twice the price of gold). The objective is to produce aromatics benzene, toluene, or xylene. Benzene and xylene are the basic building blocks of the chemical industry. 

Energy is always a part of a chemical reaction. Some reactions need energy to start. Other reactions release energy into the environment. What evidence can you find to show that a reaction between hydrogen peroxide and liver or potato is exothermic or endothermic Think about the difference between these two types of reactions. 

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