Carbon-hydrogen combustion analyzer

A large number of important chemicals are composed of hydrogen, carbon, and oxygen. The carbon-hydrogen combustion analyzer is a... 

The carbon-hydrogen combustion analyzer works because we know that compounds containing carbon and hydrogen will burn in a stream of pure oxygen, O2, to yield only carbon dioxide and water. If we can find the mass of the carbon dioxide and water separately, we can determine the mass percent of carbon and hydrogen in the compound. 

Examine Figure 6.8 to see how a carbon-hydrogen combustion analyzer works. A sample, made up of only carbon and hydrogen, is placed in a furnace. The sample is heated and simultaneously reacted with a stream... 

A schematic diagram of a carbon-hydrogen combustion analyzer. After the combustion, all the carbon in the sample is contained in the carbon dioxide. All the hydrogen in the sample is contained in the water. 

The carbon-hydrogen combustion analyzer can also be used to find the empirical formula of a compound that contains carbon, hydrogen, and one other element, such as oxygen. The difference between the mass of the sample and the mass of the hydrogen and carbon produced is the mass of the third element. 

A 1.000 g sample of a pure compound, containing only carbon and hydrogen, was combusted in a carbon-hydrogen combustion analyzer. The combustion produced 0.6919 g of water and 3.338 g of carbon dioxide. 

Explain how a carbon-hydrogen combustion analyzer can be used to determine the mass percent of carbon, hydrogen, and oxygen in a compound. 

Draw a schematic diagram of a carbon-hydrogen combustion analyzer. Write a few sentences to describe each stage of the analysis as dimethyl ether, C2H60, passes through the apparatus. 

A modified Coleman Model 33 Carbon-Hydrogen Analyzer was used to control the oxygen flow rate, to pretreat the oxygen (anhydrous magnesium perchlorate and anhydrous lithium hydroxide) and to hold the combustion tube in position. The analyzers furnace was controlled by a Fisher Model 360 Linear Temperature Programme. The rate of temperature increase was variable from 0.5 to 25 C per minute. Normally, the temperature programmer... 

Elemental analyzer An instrument that uses high-temperature combustion, typically 800-1000 °C, to convert the carbon, hydrogen, nitrogen, and sulfur constituents of a substance into gases that can be separated and measured. Some instruments can also measure oxygen contents of samples. 

A historically important form of gravimetric analysis is combustion analysis, used to determine the carbon and hydrogen content of organic compounds burned in excess O2. Modem combustion analyzers use thermal conductivity, infrared absorption, or electrochemical methods to measure the products. 

When the organic compound to be analyzed contains only carbon, hydrogen, oxygen, and sulfur after closed-flask combustion as described above, the resultant solution will be dilute sulfuric acid. In this case, it is more convenient to use acidimetry as the mode of finish. For this purpose, the solution in the Schoniger flask is transferred into a 100-mL conical flask, boiled for 2 min to remove residual hydrogen peroxide, and then titrated with 0.01 N sodium hydroxide, with methyl red as the indicator ... 

Compounds that do not decompose cleanly into their elements must be analyzed by other means. Combustion analysis is particularly useful for determining the empirical formulas of carbon-containing compounds. In combustion analysis, an accurately known mass of a compound is burned in a stream of oxygen gas. The conditions are carefully controlled so that all of the carbon in the sample is converted to carbon dioxide, and all of the hydrogen is converted to water. Certain other elements present in the sample are also converted to their oxides. 

Elemental analysis of the oils was carried out as follows carbon and hydrogen by micro combustion using a Perkin-Elmer 240 Elemental Analyzer sulphur by X-ray fluorescence using a Telsec Lab X-100 apparatus nitrogen by chemiluminescence using a Dohrmann DN-10 apparatus. 

Hafnium metal is analyzed for impurities using analytical techniques used for zirconium (19,21,22). Carbon and sulfur in hafnium are measured by combustion, followed by chromatographic or ir measurement of the carbon and sulfur oxides (19). Chromatographic measurement of liberated hydrogen follows the hot vacuum extraction or fusion of hafnium with a transition metal in an inert atmosphere (23,24). 

As an example of how combustion analysis works, imagine that we have a sample of a pure substance—say, naphthalene (often used for household moth balls). We weigh a known amount of the sample, burn it in pure oxygen, and then analyze the products. Let s say that 0.330 g of naphthalene reacts with 02 and that 1.133 g of C02 and 0.185 g of H20 are formed. The first thing to find out is the number of moles of carbon and hydrogen in the C02 and H20 products so that we can calculate the number of moles of each element originally present in the naphthalene sample. 

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