Carbon combustion analysis

Cast analysis of carbon is not appropriate for Type I. Sheet products analysis is appropriate for checking proper type of material. Extremely low carbon levels can be checked accurately usiag carbon-combustion chromatographic-type analy2ers. 

A combustion analysis was carried out on 1.621 g of a newly synthesized compound, which was known to contain only C, H, and O. The masses of water and carbon dioxide produced were 1.902 g and 3.095 g, respectively. What is the empirical formula of the compound ... 

In a combustion analysis, the amounts of C, H, and O atoms in a sample of a compound, and thus its empirical formula, are determined from the masses of carbon dioxide and water produced when the compound bums in excess oxygen. 

Determine the empirical formula of an organic compound containing carbon, hydrogen, and oxygen by combustion analysis (Example M.4). 

M.12 A compound produced as a by-product in an industrial synthesis of polymers was found to contain carbon, hydrogen, and iodine. A combustion analysis of 1.70 g of the compound produced 1.32 g of C02 and 0.631 g of H20. The mass percentage of iodine in the compound was determined by-converting the iodine in a 0.850-g sample of the compound into 2.31 g of lead(II) iodide. What is the empirical formula of the compound Could the compound also contain oxygen Explain your answer. 

In a combustion analysis, 3.21 g of a hydrocarbon formed 4.48 g of water and 9.72 g of carbon dioxide. Deduce its empirical formula and state whether it is likely to be an alkane, an alkene, or an alkyne. Explain your reasoning. 

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. 

C03-0089. Combustion analysis of 0.60 g of an unknown organic compound that contained only C, H, and O gave 1.466 g of carbon dioxide and 0.60 g of water in a combustion analysis. Mass spectral analysis showed that the compound had a molar mass around 220 g/mol. Determine the empirical formula and molecular formula. 

A PET oligomer isolation method has utilised chloroform extraction in a Parr bomb lined with a Teflon-TFE fluoro-carbon resin [40]. The analytics of fluoropolymer processing aids (combustion analysis, XRF, EUR, 19F NMR, OM) have recently been described [29]. Combustion analysis (Parr Oxygen Bomb Calorimeter) can be used for quantitative analysis... 

The assumption is made at present that elemental combustion analysis for carbon, hydrogen, and fluorine provides a good approximation to the extent of incorporation of fluoroalkyl residues, i.e. alcohols and ethers. We have ruled out trifluoromethylcarbonyl groups since no evidence is seen for their presence in either the infrared spectra or the 19F-NMR spectra. Thus, our values for percent modification reflect the best fit of the combustion data to an idealized stoichiometry for the product in Equation 1, where (m+n+o) = 100, and the percent modification (% mod.) is given by the expression [100 x (m+o)/(m+n+o)], equivalent to the number of fluoroalkyl residues per one hundred methylenes. An appropriately normalized formula was used to fit the data for polypropylene (sample 10). 

The determination of the carbon-hydrogen-oxygen content of a compound by combustion analysis involves realizing that all of the carbon has formed carbon dioxide, all of the hydrogen has formed water, and the amount of oxygen present in the original compound must be determined by difference. 

An important criticism of the use of combustion trains is that combustion is not site specific, that is all atoms in the analyte end up in the gas transferred to the IRMS. For studies of carbon isotope effects this is invariably C02. The question is especially important for carbon isotope analysis because analyte molecules of interest usually contain several different kinds of carbon atoms and therefore combustion methods average or dilute the IE s of interest. Should site specific isotope ratios be required another method of sample preparation (usually much more tedious) is necessary. Combustion methods, however, are frequently used to study nitrogen and sulfur IE s because many organic molecules are singly substituted with these atoms. Obviously, oxygen isotope effects cannot be determined using combustion trains because external oxygen is employed. Rather some type of pyrolytic sample preparation is required. 

It can be seen that the mass of carbon and hydrogen in the sample does not account for the total mass of the sample that was subjected to combustion analysis. As no other product was formed, the original sample must also have contained oxygen. The mass of oxygen in the original sample can be determined as follows ... 

A historically important form of gravimetric analysis was combustion analysis, used to determine the carbon and hydrogen content of organic compounds burned in excess 02 (Figure 27-4). Instead of weighing combustion products, modem instruments use thermal conductivity, infrared absorption, or coulometiy (with electrochemically generated reagents) to measure the products. 

Figure 27-4 Gravimetric combustion analysis for carbon and hydrogen.

The C and N Balances. The sum of the carbon and nitrogen contents of the solid and of the liquid phases was obtained by combustion for C and by Kjeldahl for N. It reproduces the initial content before reaction in all cases within the limits of the experimental error ( 0.3% for C and N). Since hydrocarbons are detected in the gas phase, this means that their total C content is smaller than the experimental error effecting the combustion analysis. 

After we receive the results of a combustion analysis from the laboratory, we need to convert the mass percentage composition to an empirical formula. For this step, we need to determine the relative number of moles of each type of atom. The simplest procedure is to imagine that we have a sample of mass 100 g exactly. That way, the mass percentage composition tells us the mass in grams of each element. Then we can use the molar mass of each element to convert these masses into moles and go on to find the relative numbers of moles of each type of atom. Let s do that for vitamin C, which was once identified in this way, and suppose that the laboratory has reported that the sample you supplied is 40.9% carbon, 4.58% hydrogen, and 54.5% oxygen. 

FIGURE M.3 The apparatus used for a combustion analysis. The masses of carbon dioxide and water produced are obtained from the differences of the masses of the collecting tubes before and after the experiment. The catalyst ensures that any CO produced is oxidized to... 

M.9 In a combustion analysis of a 0.152-g sample of the artificial sweetener aspartame, it was found that 0.318 g of carbon dioxide, 0.084 g of water, and 0.0145 g of nitrogen were produced. What is the empirical formula of aspartame The molar mass of aspartame is 294 g-mol. What is its molecular formula ... 

One of the most common methods used to determine percent composition and empirical formulas, particularly for compounds containing carbon and hydrogen, is combustion analysis. In this method, a compound of unknown composition is burned with oxygen to produce the volatile combustion products C02 and H20, which are separated and weighed by an automated instrument called a gas chromatograph. Methane (CH4), for instance, burns according to the balanced equation... 

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. 

Worked Example 3.18 shows a combustion analysis when the sample contains oxygen in addition to carbon and hydrogen. Because oxygen yields no combustion products, its presence in a molecule can t be directly detected by this method. Rather, the presence of oxygen must be inferred by subtracting the calculated masses of C and H from the total mass of the sample. 

Caproic acid, the substance responsible for the aroma of dirty gym socks and running shoes, contains carbon, hydrogen, and oxygen. On combustion analysis, a 0.450 g sample of caproic acid gives 0.418 g of H20 and 1.023 g of C02. What is the empirical formula of caproic acid If the molecular mass of caproic acid is 116.2 amu, what is the molecular formula ... 

Coniine, a toxic substance isolated from poison hemlock, contains only carbon, hydrogen, and nitrogen. Combustion analysis of a 5.024 mg sample yields 13.90 mg of C02 and 6.048 mg of H20. What is the empirical formula of coniine ... 

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