Chemical reaction, speed

According to reports from Los Alamos National Laboratory (Son 2005) nanoaluminium powders with particle size as small as eight nanometres can be combined with metal oxides to make highly energetic explosives. Called super-thermite, the combined powders are said to increase the chemical reaction speed by a factor of a thousand because of its much larger surface area. 

Figure 1. Influence of chemical reaction speed on the maximum achievable radiochemical yield. A Chemical yield 100% after 90 minutes, maximum radiochemical yield 67%. ...

Most chemical reactions speed up when the temperature goes up, and slow down if the temperature decreases. 

Temperature Affects Rate Most chemical reactions speed up when temperature increases. This is because atoms and molecules are always in motion, and they move faster at higher temperatures, as shown in Figure 15. Faster molecules collide with each other more often and with greater energy than slower molecules do, so collisions are more likely to provide enough energy to break the old bonds. This is the activation energy. 

We can answer this question qualitatively from our experience. We use refrigerators because food spoilage is retarded at low temperatures. The combustion of wood occurs at a measurable rate only at high temperatures. An egg cooks in boiling water much faster at sea level than in Leadville, Colorado (elevation 10,000 feet), where the boiling point of water is about 90°C. These observations and others lead us to conclude that chemical reactions speed up when the temperature is increased. Experiments have shown that virtually all rate constants show an exponential increase with absolute temperature, as represented in Fig. 15.10. 

Production of nanofibers that have the ability to transmit electricity creates many advantages. These nanofibers are used in the production of small electronic devices and in the fabrication of some machines. Because the surface area of the electrodes is proportional to the chemical reaction speed, electrospun nanofiber membranes are used appropriately in the production of improved high-performance batteries. 

Most chemical reactions, speed up with increases in temperature. However, high temperatures (above about 60°C) destroy, or denature, proteins by breaking up their 3-D structure. For example, the protein in an egg or a piece of meat denatures when the egg or meat is cooked. 

When the transformation of interfacial material is much faster than the system s chemical reaction speed, the whole process of extraction can occur at the kinetics zone. That means there is a slow chemical reaction in the extraction system and also the thicknesses of two-phase diffusion films that are adjacent to the interface are almost zero, or we can say the mass goes through these membranes in a very fast way. 

In region HI, bounded by the lines corresponding to Kax = 1 at the bottom and Dax = 1 at the top, the reaction zone thickness grows and the flame cannot be described by the flamelet approach based on the laminar curved flame model. As a limiting case the ideal mixing reactor model (the chemical reaction speed is neglected in comparison with the turbulent mixing time) is considered. 

Enzymes Many of the proteins in an organism act as enzymes. These proteins catalyze chemical reactions—speeding up reactions or allowing the reactions to take place at a low temperature. The reactants in an enzyme-catalyzed process are called substrates. The substrate(s) bind to the enzyme at a location called the enzyme s active site, forming an enzyme-substrate complex. This interaction... 

Krypton clathrates have been prepared with hydroquinone and phenol. 85Kr has found recent application in chemical analysis. By imbedding the isotope in various solids, kryptonates are formed. The activity of these kryptonates is sensitive to chemical reactions at the surface. Estimates of the concentration of reactants are therefore made possible. Krypton is used in certain photographic flash lamps for high-speed photography. Uses thus far have been limited because of its high cost. Krypton gas presently costs about 30/1. 

Then add a bit of NaHCOs (4 grams) and salt to saturate solution. Stir a bit more. Separate layers, Extract one more time and distill. Time depends on reaction speed. Reaction speed depends on the amount of catalyst and temperature. 60 C seems to be good, more catalyst, less time. More temperature May be more byproducts, this is what happen when acetic acid is the solvent. Probably a good way will be also acetic acid and 40-50 C, but dual phase is easy to extract ans uses less chemicals. 

Air-drying epoxy paints are not required to be stoved due lo chemical reaction at about I20°C, which may affect its hardness. To speed up the curing, it may be stoved at a maximum temperature of, say, 60-80°C as noted in column 2. 

Modeling a single parcel of air as it is being moved along allows the chemical reactions in the parcel to be modeled. A further advantage of trajectory models is that only one trajectory is required to estimate the concentration at a given endpoint. This minimizes calculation because concentrations at only a limited number of points are required, such as at stations where air quality is routinely monitored. Since wind speed and direction at the top and the bottom of the column are different, the column is skewed from the vertical. However, for computational purposes, the column is usually assumed to remain vertical and to be moved at the wind speed and direction near the surface. This is acceptable for urban application in the daytime, when winds are relatively uniform throughout the lower atmosphere. 

When two-phase mass transfer is required to supply reactants by mixing for a chemical reaction, the most important factor to consider is whether the mass transfer controls the operation or whether the chemical reaction controls it. This can be done by increasing the mixer speed to a point w here mass transfer effects become very high and the operation is limited by the chemical reaction. 

Catalyst A substance used to speed up a chemical reaction, including the transformation of certain pollutants present in a combustion process. 

For thermoset-matrix materials, heat is usually added as a catalyst to speed the natural chemical reaction of polymerization. Two-part epoxies, such as found in your local hardware store, consist of a tube of epoxy and a tube of chemical hardener that react when mixed. Heat... 

It will be realised that the strength of an odour may suffer successive diminutions in the process of smelling. It will be governed firstly, by the vapour pressure. of the odoriferous body, secondly, by the degree of solubility of the substance in water, thirdly, to its relative solubility in the lipoid fats with respect to that in water, and, lastly, to the speed of the chemical reaction. To a less extent the type of odour is similarly governed and this may account for the many shades of odour that exist. It is obvious that too much importance must not be placed on the chemical aspect of the problem, especially as regards the strength of an odour. 

Models for description of liquids should provide us with an understanding of the dynamic behavior of the molecules, and thus of the routes of chemical reactions in the liquids. While it is often relatively easy to describe the molecular structure and dynamics of the gaseous or the solid state, this is not true for the liquid state. Molecules in liquids can perform vibrations, rotations, and translations. A successful model often used for the description of molecular rotational processes in liquids is the rotational diffusion model, in which it is assumed that the molecules rotate by small angular steps about the molecular rotation axes. One quantity to describe the rotational speed of molecules is the reorientational correlation time T, which is a measure for the average time elapsed when a molecule has rotated through an angle of the order of 1 radian, or approximately 60°. It is indirectly proportional to the velocity of rotational motion. 

Enzymes are complex molecules, usually proteins, that speed up chemical reactions. Figure 2 illustrates in graphic form how enzymes function. To fully understand Figure 2, imagine a chemical reaction in which a part of one compound is transferred to another compound ... 

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