(Nitrogen, hydrogen, oxygen, carbon dioxide, and other elements cause weld defects if introduced to the weld pool.) After a while it was discovered that argon has some advantages over helium. Because argon is heavier than helium, less flow rate is needed. The lower flow rate requirement makes argon better for flat welding. Helium is good for overhead, because it is lighter and thus flows upward.
Heat Capacity... The Heat Capacity itself is extensive (scales with the size of system), but we can think of making this quantity intensive (making it an intrinsic property of the material) by defining related quantities: the Molar Heat Capacity is defined as the Heat Capacity of a homogeneous pure compound (or element) divided by the the number of moles of that compound (or element) the Specific Heat is defined as the Heat Cpacity of a homogeneous sample divided by its mass. The Heat Capacity of any substance is positive. The Heat Capacity is discontinuous at phase transitions. For a gas, the Heat capacity depends on how one does the heating.
A good example of where a large surface area is used for a fast rate of diffusion is in the alveoli of the lungs. Alveoli are the ‘air sacs’ at the end of the airways in the lungs where the exchange of carbon dioxide and oxygen takes place between the air in the alveoli and the blood in capillaries. Both the alveoli and the capillaries are extremely thin, only one cell thick, which increases the rate of diffusion, but the alveoli also have an extremely large surface area. This is because they take the shape of small spheres, giving them a large surface area to volume ratio. Another example of where surface area is maximised to increase the rate of diffusion is in the small intestine.
The half reactions for this system are: Oxidation of 〖Fe〗^(2+): 〖Fe〗^(2+)→ 〖Fe〗^(3+)+1e^- Reduction of 〖MnO〗_4^-: 〖MnO〗_4^-+8H_3 O^++5e^-→ 〖Mn〗^(2+)+12H_2 O Which produces the following overall equation: 〖MnO〗_4^-+8H_3 O^++5〖Fe〗^(2+)→5〖Fe〗^(3+)+〖Mn〗^(2+)+12H_2 O Equilibrium is initially obtained at a very slow rate, therefore the titration is carried out in the presence of excess sulphuric acid (H_2 〖SO〗_4) at a high temperature; in order to drastically increase the rate at which equilibrium is attained. Potassium permanganate acts as its own satisfactory indicator since the reagent 〖MnO〗_4^- anion appears to be an intense purple colour while the product 〖Mn〗^(2+) cation has a colourless appearance. However, the end point must be read quickly as the permanganate end point gradually fades due to the 〖MnO〗_4^- reacting with the 〖Mn〗^(2+) that was formed during the titration. When performing the titration, one must be cautious as side reactions can occur and these side reactions must be prevented using appropriate chemical measures. If an insufficient amount of acid was
The effect of heat on the expansion of gases is stated in Charles' Law. A gas occupies 1/273.15 more space for each 1° C. rise in temperature and, conversely, 1/273.15 less space for each 1° C. drop in temperature. This fact enabled scientists to determine absolute zero (-273.15° C.), the temperature at which all molecules theoretically stop moving. A gas can be made to expand without the addition of outside heat if the pressure confining the gas is reduced. This principle is stated in Boyle's Law.
Low density polyethylene (LDPE) – involves an older gas phase process (still used) with conditions: high pressure (1000-3000 times atmospheric), high temperature (300°C) and an initiator (an organic peroxide e.g. dibutyl peroxide, or oxygen). The resultant product has significant chain branching due to alkyl groups replacing hydrogen atoms on some carbon atoms. Consequently, the alkane chains cannot pack together in an orderly fashion, resulting in low densities and weak dispersion forces; therefore LDPE is soft, flexible and has a low melting point. The initiator isn’t strictly a catalyst as it is involved in the actual formation (one initiator molecule per ½ polymer molecule).
There is about 1700 kPa (250 psi) pressure in the tank when full. Acetylene when combined with oxygen burns at a temperature of 3200 °C to 3500 °C (5800 °F to 6300 °F), highest among commonly used gaseous fuels. As a fuel acetylene's primary disadvantage, in comparison to other fuels, is high cost. As acetylene is unstable at a pressure roughly equivalent to 33 feet/10 meters underwater, water submerged cutting and welding is reserved for hydrogen rather than acetylene. Compressed gas cylinders containing oxygen and MAPP gas.
The fuel and air are mixed outside of the cylinder; once they are both injected they require a spark to ignite. B) A diesel engine uses a much higher compression ration than a gasoline engine. The heat created in a diesel engine by this higher compression is therefore, much greater than
The one of the most important current benefits of geothermal energy is that it is essentially limitless and is considered clean, producing around one-sixth of the carbon dioxide that a comparative clean natural-gas- power plant produces. Costs of geothermal energy are initially expensive but much lower than other sources to operate after the initial costs. Drilling and construction of power plants and pipelines can be relatively high but looking at the cost long-term, it is significantly
In Ohaake in New Zealand about 320 gm of C02 is produced for each KW hour of electricity produced against 950 to 960 gm. if coal was used. Limitations Geothermal energy is a proven economical resource with energy technology. It has some environmental problems: 1. The steam brings hydrogen sulphide gas to the surface and pollutes the air unless controls are instituted.