Oxygen combustion reactions

Combustion is an oxidation-reduction reaction between a nonmetallic material and molecular oxygen. Combustion reactions are characteristically exothermic (energy releasing). A violent combustion reaction is the formation of water from hydrogen and oxygen. As discussed in Section 9.5, the energy from this reaction is used to power rockets into space. More common examples of combustion include the burning of wood and fossil fuels. The combustion of these and other carbon-based chemicals forms carbon dioxide and water. Consider, for example, the combustion of methane, the major component of natural gas ... 

Chemical reactions that have a common reactant may be grouped together. Reactions involving oxygen, combustion reactions, are such a class. 

A homogeneous chemical reaction is a reaction where the reactants and products are all in one phase and the reaction can proceed anywhere throughout the volume of the considered phase/system. The hydrogen-oxygen combustion reaction is an example of a homogeneous chemical reaction (assuming that the water is produced in the gas phase). Many gas-gas and nuclear decay reactions are homogeneous. 

In the reaction phase, hydrocarbons react with oxygen according to the highly exothermic combustion reaction. Practically all of the available oxygen is consumed in this phase. 

The three T s of combustion—time, temperature, and turbulence—govern the speed and completeness of the combustion reaction. For complete combustion, the oxygen must come into intimate contact with the combustible molecule at sufficient temperature and for a sufficient length of time for the reaction to be completed. Incomplete reactions may result in the generation of aldehydes, organic acids, carbon, and carbon monoxide. 

Stoichiometric Concentration (Used by permission of Frank T. Bodurtha, Inc., New London, New Hampshire). In a combustion reaction in air, the stoichiometric concentration, Cjt, of any reac tant is the concentration theoretically required for complete conversion by reacting completely with oxygen. For example, for the combustion of propane in air ... 

Since the oxygen is contained in air, which also has nitrogen, the combustion reaction can be written as follows ... 

The saturated hydrocarbons are relatively inert except at high temperatures. For example, sodium metal is usually stored immersed in an alkane such as kerosene (8 to 14 carbon atoms) to protect it from reaction with water or oxygen. Combustion is almost the only important chemical reaction of the alkanes. That reaction, however, makes the hydrocarbons one of the most important energy sources of our modern technology. 

H.15 Write a balanced equation for the complete combustion (reaction with oxygen) of liquid heptane, C7H)6, a component typical of the hydrocarbons in gasoline, to carbon dioxide gas and water vapor. 

Positive Ion-Molecule Reactions. Some of the important ions identified in hydrocarbon/air or oxygen combustion are presented in Table II. With the exception of CHO+ and possibly C3H3+, all the ions are produced in ion-molecule reactions. 

C04-0009. Combustion reactions require molecular oxygen. In an automobile the fuel-injection system must be adjusted to provide the right mix of gasoline and air. Compute the number of grams of oxygen required to react completely with 1.00 L of octane (CgHig,p = 0.80 g/mL). What masses of water and carbon dioxide are produced in this reaction ... 

As an example that uses structural formulas and Equation, consider the energy change that takes place during the combustion reaction of propane (C3 Hg). Recall from Chapter 3 that combustion is a reaction with molecular oxygen. The products of propane combustion are carbon dioxide and water ... 

Figure 6-17 illustrates a constant-volume calorimeter of a type that is often used to measure q for combustion reactions. A sample of the substance to be burned is placed inside the sealed calorimeter in the presence of excess oxygen gas. When the sample bums, energy flows from the chemicals to the calorimeter. As in a constant-pressure calorimeter, the calorimeter is well insulated from its surroundings, so all the heat released by the chemicals is absorbed by the calorimeter. The temperature change of the calorimeter, with the calorimeter s heat capacity, gives the amount of heat released in the reaction. 

It is very difficult to handle since it combusts spontaneously in air. The fire is difficult to put out and requires special extinguishing agents. With liquid oxygen the reaction leads to a violent detonation. The surface texture of titanium seems to be an important element in the violence of the effects obtained. 

As illustrated on Figure 7.8, the DPF regeneration step is just a soot particles combustion reaction (soot is mainly composed by a carbon matrix), which requires a temperature in the range of 600°C and oxygen presence in the exhaust gases. 

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