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Calorimetry examples

An excellent example of work of this type is given by the investigations of Benson and co-workers [127, 128]. They found, for example, a value of = 276 ergs/cm for sodium chloride. Accurate calorimetry is required since there is only a few calories per mole difference between the heats of solution of coarse and finely divided material. The surface area of the latter may be determined by means of the BET gas adsorption method (see Section XVII-5). [Pg.280]

With most non-isothemial calorimeters, it is necessary to relate the temperature rise to the quantity of energy released in the process by determining the calorimeter constant, which is the amount of energy required to increase the temperature of the calorimeter by one degree. This value can be detemiined by electrical calibration using a resistance heater or by measurements on well-defined reference materials [1], For example, in bomb calorimetry, the calorimeter constant is often detemiined from the temperature rise that occurs when a known mass of a highly pure standard sample of, for example, benzoic acid is burnt in oxygen. [Pg.1902]

Figure 6.11 shows a famous example of the application of isothermal calorimetry. Gordon (1955) deformed high-purity copper and annealed samples in his precision calorimeter and measured heat output as a function of time. In this metal, the heat output is strictly proportional to the fraction of metal recrystallised. [Pg.242]

Common examples of the high Tg macromers are based on polystyrene or polymethylmethacrylate (PMMA) polymers of sufficiently high molecular weight to have a high T (typically on the order of 70-100°C as measured by differential scanning calorimetry) and also to make them immiscible with the acrylic polymer backbone once the solvent or heat has been removed. Typical molecular weight of the polystyrene or PMMA macromers is on the order of 5000-10,000 Da. Their generic structure can be pictured as in Fig. 13 (shown there for polystyrene). [Pg.501]

Differential scanning calorimetry (DSC) is fast, sensitive, simple, and only needs a small amount of a sample, therefore it is widely used to analyze the system. For example, a polyester-based TPU, 892024TPU, made in our lab, was blended with a commercial PVC resin in different ratios. The glass transition temperature (Tg) values of these systems were determined by DSC and the results are shown in Table 1. [Pg.138]

In recent years, fluorine bomb calorimetry has been used effectively. A number of substances that will not burn in oxygen will burn in fluorine gas. The heat resulting from this fluorine reaction can be used to calculate AfH°m. For example, Murray and 0 Hare have reacted GeS2 with fluorine and measured ArH°. The reaction is... [Pg.452]

A number of analytical techniques such as FTIR spectroscopy,65-66 13C NMR,67,68 solid-state 13 C NMR,69 GPC or size exclusion chromatography (SEC),67-72 HPLC,73 mass spectrometric analysis,74 differential scanning calorimetry (DSC),67 75 76 and dynamic mechanical analysis (DMA)77 78 have been utilized to characterize resole syntheses and crosslinking reactions. Packed-column supercritical fluid chromatography with a negative-ion atmospheric pressure chemical ionization mass spectrometric detector has also been used to separate and characterize resoles resins.79 This section provides some examples of how these techniques are used in practical applications. [Pg.407]

Calculate energy changes from calorimetry data and write a thermochemical equation (Examples 6.4 and 6.7). [Pg.378]

Constant-pressure calorimetry requires only a thermally insulated container and a thermometer. A simple, inexpensive constant-pressure calorimeter can be made using two nested Styrofoam cups. Figure 6-16 shows an example. The inner cup holds the water bath, a magnetic stir bar, and the reactants. The thermometer is inserted through the cover. The outer cup provides extra thermal insulation. [Pg.390]

Example illustrates an application of constant-pressure calorimetry. Our Box (see page 234) describes uses of constant-pressure calorimetry in studies of biological systems. [Pg.391]

Calorimetry shows that the rates of metabolism of plant tissues vary widely with species, with cell types, and with environmental conditions. This provides a means of exploring the mechanisms by which various agents influence the health of a plant community. Studies are being done on beneficial agents such as growth promoters and detrimental ones such as atmospheric pollutants. For example, a correlation has been found between the metabolic heat rates and the extent of damage to pine needles by ozone. [Pg.395]

These are just some of the ways in which calorimetry is used in contemporary biological research. Our examples highlight studies at the cellular level, but ecologists also use calorimetry to explore the energy balances In ecosystems, and whole-organism biologists have found ways to carry out calorimetric measurements on fish, birds, reptiles, and mammals. Including humans. [Pg.396]

In our world, most chemical processes occur in contact with the Earth s atmosphere at a virtually constant pressure. For example, plants convert carbon dioxide and water into complex molecules animals digest food water heaters and stoves bum fiiel and mnning water dissolves minerals from the soil. All these processes involve energy changes at constant pressure. Nearly all aqueous-solution chemistry also occurs at constant pressure. Thus, the heat flow measured using constant-pressure calorimetry, gp, closely approximates heat flows in many real-world processes. As we saw in the previous section, we cannot equate this heat flow to A because work may be involved. We can, however, identify a new thermod mamic function that we can use without having to calculate work. Before doing this, we need to describe one type of work involved in constant-pressure processes. [Pg.399]

In Example, we used calorimetry data to determine that the energy change when one mole of octane bums is... [Pg.403]

Equation can also be used to calculate the standard enthalpy of formation of a substance whose formation reaction does not proceed cleanly and rapidly. The enthalpy change for some other chemical reaction involving the substance can be determined by calorimetric measurements. Then Equation can be used to calculate the unknown standard enthalpy of formation. Example shows how to do this using experimental data from a constant-volume calorimetry experiment combined with standard heats of formation. [Pg.410]

Table 5.4-9 gives examples of the use of reaction calorimetry in process development and optimization. [Pg.304]

Note that the 1,2-diequatorial substituted examples in Fig 7.10(c and d) are individual stereoisomers. The corresponding cis-species (Fig. 7.11b) is not another conformation, but another stereo isomer. The experimentally by calorimetry determined energy difference between the isomers is 6.5 kJ mol" . [Pg.170]

Classical methods for the investigation of complex formation equilibria in solution (UV/Vis spectrometry, thermochemical and electrochemical techniques) are still in use (for an appraisal of these and other methods see, e.g., ref. 22). Examples for the determination of the ratio of metal to ligand in an Hg-protein complex by UV spectrometry are given in ref. 23, for the study of distributions of complex species of Cd in equilibria by combined UV spectrometry and potentio-metry in ref. 24 and by potentiometry alone in ref. 25, and for the combination of calorimetry and potentiometry to obtain thermodynamic data in ref. 26. [Pg.1254]

We use differential scanning calorimetry - which we invariably shorten to DSC - to analyze the thermal properties of polymer samples as a function of temperature. We encapsulate a small sample of polymer, typically weighing a few milligrams, in an aluminum pan that we place on top of a small heater within an insulated cell. We place an empty sample pan atop the heater of an identical reference cell. The temperature of the two cells is ramped at a precise rate and the difference in heat required to maintain the two cells at the same temperature is recorded. A computer provides the results as a thermogram, in which heat flow is plotted as a function of temperature, a schematic example of which is shown in Fig. 7.13. [Pg.150]

The progress of polymer degradation may be followed by a wide variety of techniques, some of them being mentioned at the right column in the Bolland-Gee scheme (Scheme 2). There are techniques that directly monitor some of the elementary reaction steps such as, for example, oxygen absorption (reaction 2), differential scanning calorimetry (DSC) (reaction 3), chemiluminescence (reaction 11) analytical and/or spectral methods of determination of hydroperoxides, etc. [Pg.461]

It is evident, however, from the preceding examples that the detailed analysis of surface interactions by means of adsorption calorimetry is... [Pg.253]


See other pages where Calorimetry examples is mentioned: [Pg.270]    [Pg.193]    [Pg.364]    [Pg.270]    [Pg.193]    [Pg.364]    [Pg.1907]    [Pg.1916]    [Pg.2841]    [Pg.410]    [Pg.493]    [Pg.138]    [Pg.418]    [Pg.10]    [Pg.328]    [Pg.1087]    [Pg.35]    [Pg.113]    [Pg.541]    [Pg.103]    [Pg.53]    [Pg.96]    [Pg.400]    [Pg.599]    [Pg.601]    [Pg.64]    [Pg.303]    [Pg.431]    [Pg.75]    [Pg.191]    [Pg.240]   
See also in sourсe #XX -- [ Pg.81 ]

See also in sourсe #XX -- [ Pg.118 ]




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