Heat evolved

CjHiaNO, [Mc3NCH= CH2] OH. A liquid forming a crystalline trihydrate, It is present free and combined in brain and other animal and vegetable products and is formed as a product of putrefaction of lecithin. It can be prepared synthetically from choline and decomposes easily to trimethylamine. neutralization, heat of The amount of heat evolved when I g equivalent of an acid is neutralized by 1 g equivalent of a base. For strong acids and strong bases in dilute solution the only reaction which occurs is H -h OH ---> H2O and the heat of neutral-... 

If the process is carried out at constant volume, the heat evolved Qi will be equal to an energy change AE2 or, per mole of adsorbate, qi = Ae2 (small capital letters will be used to denote mean molar quantities). Alternatively, the process may be... 

The heat evolved will now be a differential heat of adsorption, equal at constant volume to Qd or per mole, to qd - AI2, where Ae2 is the change in partial molar energy. It follows that... 

The integral heat of adsorption Qi may be measured calorimetrically by determining directly the heat evolution when the desired amount of adsorbate is admitted to the clean solid surface. Alternatively, it may be more convenient to measure the heat of immersion of the solid in pure liquid adsorbate. Immersion of clean solid gives the integral heat of adsorption at P = Pq, that is, Qi(Po) or qi(Po), whereas immersion of solid previously equilibrated with adsorbate at pressure P gives the difference [qi(Po) differential heat of adsorption q may be obtained from the slope of the Qi-n plot, or by measuring the heat evolved as small increments of adsorbate are added [123]. 

Rate effects may not be chemical kinetic ones. Benson and co-worker [84], in a study of the rate of adsorption of water on lyophilized proteins, comment that the empirical rates of adsorption were very markedly complicated by the fact that the samples were appreciably heated by the heat evolved on adsorption. In fact, it appeared that the actual adsorption rates were very fast and that the time dependence of the adsorbate pressure above the adsorbent was simply due to the time variation of the temperature of the sample as it cooled after the initial heating when adsorbate was first introduced. 

The sulphates of the alkali and alkaline earth metals and man-ganese(II) are stable to heat those of heavier metals decompose on heating, evolving sulphur trioxide and leaving the oxide or the metal ... 

Transfer the diazotised solution to a 600 mi. beaker, add 150 ml. of benzene, and stir the mixture vigorously to obtain an intimate mixture of the two liquids. Then again maintain the temperature at about 5° (by ice-salt cooling because of the heat evolved) whilst 27 ml. of 20% aqueous sodium hydroxide solution are added from a dropping-fiinnel during 40-50 minutes. When the addition of the alkali is complete, remove the ice-water bath, and allow the stirred mixture to reach room temperature. 

Under the action of strong organometallic bases, thiazole undergoes hydrogen-metal interconversion. Ethylmagnesium bromide reacts at 0°C with thiazole in ether to form an insoluble adduct that upon heating evolves ethane almost quantitatively and affords an etheral solution of thiazol-2-ylmagnesium bromide (155) (12). Proof of the structure of this... 

By allowing compounds to react in a calorime ter It IS possible to measure the heat evolved in an exothermic reaction or the heat absorbed in an en dothermic reaction Thousands of reactions have been studied to produce a rich library of thermo chemical data These data take the form of heats of reaction and correspond to the value of the enthalpy change AH° for a particular reaction of a particular substance... 

The heat evolved on burning an alkane increases with the number of car bon atoms The relative stability of isomers may be determined by com paring their respective heats of combustion The more stable of two iso mers has the lower heat of combustion... 

Heat of combustion (Section 2 18) Heat evolved on combus tion of a substance It is the value of — A//° for the combus tion reaction... 

In the one-stage process (Fig. 2), ethylene, oxygen, and recycle gas are directed to a vertical reactor for contact with the catalyst solution under slight pressure. The water evaporated during the reaction absorbs the heat evolved, and make-up water is fed as necessary to maintain the desired catalyst concentration. The gases are water-scmbbed and the resulting acetaldehyde solution is fed to a distUlation column. The tad-gas from the scmbber is recycled to the reactor. Inert materials are eliminated from the recycle gas in a bleed-stream which flows to an auxdiary reactor for additional ethylene conversion. 

The principal advantage to this method is that the heat evolved for each carbon—fluorine bond formed, 192.5 kj/mol (46 kcal/mol), is much less than that obtained in direct fluorination, 435.3 kJ/mol (104 kcal/mol). The reaction yields are therefore much higher and less carbon—carbon bond scisson occurs. Only two metal fluorides are of practical use, Agp2 and GoF. ... 

Anhydrous sodium tripolyphosphate is slow to hydrate in contact with the atmosphere under normal ambient conditions and generally remains free-flowing. If the relative humidity is below a critical relative humidity, which is different for both anhydrous forms of STP and dependent on temperature, hydration does not take place. For prolonged storage at room temperature, relative humidities above ca 60% in the air result in water absorption. For shorter periods, high levels of humidity can be tolerated. However, even at higher humidities, the amount of water absorbed is small. The heats evolved from vapor hydration of STP-I and -II have been estimated at 343 and 334 kj /mol (82.0 and 79.9 kcal/mol), respectively (25). 

This reaction is the basis for the Fluff detergent process (26). The heat evolved coupled with the hydration of the STP is sufficient to dry the reaction mass to yield a light density laundry detergent. Requiring a low capital investment, the Fluff process has found use in less-industrialized countries. 

Table 3. Dissolution Time of Dry Alum, Al2(S04)3l4.3H20, and Heat Evolved on Mixing...

The heat of reaction AH is given in joules per gram mole of ammonia formed. Equation 22 ignores the heat of mixing which must be taken into account for apphcation to industrial situations (21,22). The heat evolved in synthesis at 370—540°C is approximately 54,430 kj/mol (23, 400 Btu/lb-mol). 

Heat evolves when wool, dry mass of 1 kg, at a particular regain is immersed in water. 

Trisodium citrate is more widely used than any of the other salts of citric acid. It is generally made by neutralization of a water solution of citric acid using sodium hydroxide. The neutralization reaction is highly exothermic giving off 1109 J/g of citric acid. To conserve energy, the heat evolved can be used in the sodium citrate concentration and crystallization steps. 

Heat evolved, in Idlogram-calories per gram formula weight, on solution in water at 18 C. Computed from data in Bichowsky and Rossini, Theimochemishy of Chemical Substances, Reinhold, New York, 1936. 

Potential System with sufficient exothermic (heat evolving) capacity... 

Heat Evolved in Plate (He) - Heat Conducted from Plate (Gc)... 

Consequently the heat evolved in plate (n) (He) will be given by... 

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