combustion analysis

(noun)

Using burning to determine the elemental composition of an organic compound. The compound is burned, the products are collected and weighed, and the composition is determined.

Related Terms

Examples of combustion analysis in the following topics:

  • Combustion Analysis

    • Combustion analysis is commonly used to determine the relative ratios of carbon, hydrogen, and oxygen in organic compounds.
    • Combustion analysis is an elemental analytical technique used on solid and liquid organic compounds.
    • Combustion analysis is commonly used to analyze samples of unknown chemical formula.
    • In combustion analysis, the products, carbon dioxide and water vapor, are trapped by absorption onto reactive solids located in tubes above the reaction vessel.
    • Combustion analysis can also be performed using a CHN analyzer, which uses gas chromatography to analyze the combustion products.

  • Empirical Formulas

    • For example, combustion analysis can be used in the following manner:

  • Reaction Energetics

    • In the combustion of methane, for example, all six bonds in the reactant molecules are broken, and six new bonds are formed in the product molecules (equation 1).
    • Were this true, no life would exist on Earth, because the numerous carbon compounds that are present in and essential to all living organisms would spontaneously combust in the presence of oxygen to give carbon dioxide-a more stable carbon compound.
    • The combustion of methane (eq.1), for example, does not occur spontaneously, but requires an initiating energy in the form of a spark or flame.
    • Often it is heat, as noted above in reference to the flame or spark that initiates methane combustion.
    • These facts lead to the following general analysis of reaction rates.

  • Combustion

    • The combustion of carbon compounds, especially hydrocarbons, has been the most important source of heat energy for human civilizations throughout recorded history.
    • Precise heats of combustion measurements can provide useful iinformation about the structure of molecules.
    • From the previous discussion, we might expect isomers to have identical heats of combustion.
    • Thus, the heat of combustion of pentane is –782 kcal/mole, but that of its 2,2-dimethylpropane (neopentane) isomer is –777 kcal/mole.
    • The following table lists heat of combustion data for some simple cycloalkanes and compares these with the increase per CH2 unit for long chain alkanes.

  • Constant-Volume Calorimetry

    • Constant-volume calorimeters, such as bomb calorimeters, are used to measure the heat of combustion of a reaction.
    • A bomb calorimeter is a type of constant-volume calorimeter used to measure a particular reaction's heat of combustion.
    • As such, bomb calorimeters are built to withstand the large pressures produced from the gaseous products in these combustion reactions.
    • Once the sample is completely combusted, the heat released in the reaction transfers to the water and the calorimeter.
    • A schematic representation of a bomb calorimeter used for the measurement of heats of combustion.

  • Indoor Pollution: CO and CO2

    • Carbon monoxide and carbon dioxide are products of combustion reactions; in large amounts, carbon monoxide can cause suffocation.
    • Carbon dioxide and carbon monoxide are the products of combustion reactions, such as the burning of coal, wood, and natural gas, or the use of modern combustion engines (most frequently used in cars).
    • Carbon monoxide is often the product of incomplete combustion reactions.
    • In the presence of adequate oxygen, combustion reactions will usually produce carbon dioxide.

  • Types of Redox Reactions

    • The five main types of redox reactions are combination, decomposition, displacement, combustion, and disproportionation.
    • Keep this in mind as we look at the five main types of redox reactions: combination, decomposition, displacement, combustion, and disproportion.
    • Combustion reactions always involve oxygen and an organic fuel.
    • In the following image, we see methane combusting to release energy.
    • This is an example of a combustion reaction, a redox process.

  • Physical and Chemical Properties of Matter

    • Heat of combustion is the energy released when a compound undergoes complete combustion (burning) with oxygen.
    • The symbol for the heat of combustion is ΔHc.

  • Halogenation

    • Unlike the complex transformations of combustion, the halogenation of an alkane appears to be a simple substitution reaction in which a C-H bond is broken and a new C-X bond is formed.
    • Consequently, an understanding of the preference for substitution at 2º and 3º-carbon atoms must come from an analysis of this first step.
    • An insightful analysis of this subject has been published by Andreas A.

  • Reactions of Alkanes

    • The most important reaction that alkanes undergo is combustion.
    • The combustion of methane is shown: