Arrhenius Equation Formula and Example

In 1889, Svante Arrhenius formulated the Arrhenius equation, which relates reaction rate to temperature. A broad generalization of the Arrhenius equation is to say the reaction rate for many chemical reactions doubles for every increase in 10 degrees Celsius or Kelvin. While this rule of thumb isnt always accurate, keeping it in mind is a good way to check whether a calculation made using the Arrhenius equation is reasonable. Formula There are two common forms of the Arrhenius equation. Which one you use depends on whether you have an activation energy in terms of energy per mole (as in chemistry) or energy per molecule (more common in physics). The equations are essentially the same, but the units are different. The Arrhenius equation as its used in chemistry is often stated according to the formula: k Ae-Ea/(RT) k is the rate constantA is an exponential factor that is a constant for a given chemical reaction, relating the frequency of collisions of particlesEa is the activation energy of the reaction (usually given in Joules per mole or J/mol)R is the universal gas constantT is the absolute temperature (in Kelvins) In physics, the more common form of the equation is: k Ae-Ea/(KBT) k, A, and T are the same as beforeEa is the activation energy of the chemical reaction in JouleskB is the Boltzmann constant In both forms of the equation, the units of A are the same as those of the rate constant. The units vary according to the order of the reaction. In a first-order reaction, A has units of per second (s-1), so it may also be called the frequency factor. The constant k is the number of collisions between particles that produce a reaction per second, while A is the number of collisions per second (which may or may not result in a reaction) that are in the proper orientation for a reaction to occur. For most calculations, the temperature change is small enough that the activation energy is not dependent on temperature. In other words, its usually not necessary to know the activation energy to compare the effect of temperature on reaction rate. This makes the math much simpler. From examining the equation, it should be apparent the rate of a chemical reaction may be increased by either increasing the temperature of a reaction or by decreasing its activation energy. This is why catalysts speed up reactions! Example Find the rate coefficient at 273 K for the decomposition of nitrogen dioxide, which has the reaction: 2NO2(g) → 2NO(g) O2(g) You are given that the activation energy of the reaction is 111 kJ/mol, the rate coefficient is 1.0 x 10-10 s-1, and the value of R is 8.314 x 10-3 kJ mol-1K-1. In order to solve the problem, you need to assume A and Ea dont vary significantly with temperature. (A small deviation might be mentioned in an error analysis, if you are asked to identify sources of error.) With these assumptions, you can calculation the value of A at 300 K. Once you have A, you can plug it into the equation to solve for k at the temperature of 273 K. Start by setting up the initial calculation: k Ae-Ea/RT 1.0 x 10-10 s-1 Ae(-111 kJ/mol)/(8.314 x 10-3 kJ mol-1K-1)(300K) Use your scientific calculator to solve for A and then plug in the value for the new temperature. To check your work, notice the temperature decreased by nearly 20 degrees, so the reaction should only be about a fourth as fast (decreased by about half for every 10 degrees). Avoiding Mistakes in Calculations The most common errors made in performing calculations are using constant that have different units from each other and forgetting to convert Celsius (or Fahrenheit) temperature to Kelvin. Its also a good idea to keep the number of significant digits in mind when reporting answers. Arrhenius Plot Taking the natural logarithm of the Arrhenius equation and rearranging the terms yields an equation that has the same form as the equation of a straight line (y mxb): ln(k) -Ea/R (1/T) ln(A) In this case, the x of the line equation is the reciprocal of absolute temperature (1/T). So, when data is taken on the rate of a chemical reaction, a plot of ln(k) versus 1/T produces a straight line. The gradient or slope of the line and its intercept can be used to determine the exponential factor A and the activation energy Ea. This is a common experiment when studying chemical kinetics.

Essay about The Hero Monomyth in Sons of Anarchy - 665 Words

Claire Stemmer 16 March 2015 HUM 115-502 Prof. Streit SWA 4: Patterns of the Hero Monomyth in Sons of Anarchy In his renowned work, The Hero with a Thousand Faces, Joseph Campbell defined the essential stages of the Heroic Journey, using examples from a wide range of myths and stories. His objective was not only to establish the framework for hero tales, but also to convey why these elements of the monomyth prevail in so many different works. Campbell’s view states that â€Å"the hero myth is really written about every human being: we are all heroes struggling to accomplish our adventure† (Whomsley, 185). From this perspective, it seems justified that these patterns continue to appear in so many stories adventure and heroism; we all want our†¦show more content†¦The element of the Hero’s Journey that the show most clearly reflects is the concept of â€Å"Atonement with the Father†. Central to the plotline is the relationship between father and son, and the implications are manifold. Clay Morrow fills the role of the mythical father figure, as well as one of the show’s antagonists despite his actual familial relationship with Jax. In Campbell’s analysis of the Hero’s Journey, the father figure plays a huge part in the hero’s transformation process: â€Å"His role is to test the hero to ascertain his worthiness† (190). The Father can also symbolize the source of evil that the hero must eliminate: â€Å"The hero’s quest, if successful, incorporates the defeat of an ogre or villain who represents the fearsome aspect of the father† (190). The point in the series where Jax ends Clay’s life is a truly pivotal moment in his heroic journey, as it signifies our protagonist stepping into a new position of leadership and responsibility. In The Hero with a Thousand Faces, Joseph Campbell delineated the essential features found in myths and stories of heroes and heroic journeys. His purpose in doing so was partly to elucidate the notion that we are all heroes on the course of our own adventures. Looking at contemporary works of fiction through the lens of the heroic monomyth, we are able to make connections between our own heroes and ourselves. Jax

What is Ethnobotany Free Essays

Introduction Plants have long been used in traditional medicine. They have been known as rich sources of modern medicines, drugs and drug products because they produce a host of bioactive molecules, which serve as chemical defenses against predation or infection. By the mid-1980s, most pharmaceutical manufacturers had abandoned exploring folk practices including plant derivatives in their search for new drugs because of the discovery of microorganisms and fungi including the advances of synthetic chemistry in the production of medicines and antibiotics. We will write a custom essay sample on What is Ethnobotany or any similar topic only for you Order Now However, to date, the pendulum is beginning to swing back towards the appreciation of plants used in traditional medicine that has potential novel therapeutic agents. The World Health Organization (WHO) reported that 65-80% of the world’s population mostly in developing countries; widely depend on plants for primary healthcare due to poverty and lack of access to modern medicine [1]. Several ethnobotany studies support this report. [2, 3, 4, 5]. Ethnobotany is the study of the interaction between plants and people in their local environment [5, 6] The ethnobotanical approach is actually one of the several methods in choosing plants for pharmacological studies. There are about less than 0.5% of the estimated 265,000 flowering species on earth which have been studied exhaustively for their chemical composition and medicinal value. Ethnobotany studies of medicinal plants have been used in various ways such as to test hypothesis of use and knowledge, describing the use of plants in a given community or listing plants for food, therapeutic and other ethnobotanical purposes[7]. Herbal medicines that have been based on traditional knowledge are estimated at about 60 billion US dollars in the world market today. Traditional medicine has always been recognized as an important tool for the development of novelties in drug discovery [8]. Traditional medicinal practices through indigenous knowledge are common among tribes and local folks as their primary health care system [9, 10, 11, and 12]. Hence, traditional knowledge of medicinal plants as known by indigenous healers and local folks are not only useful for conservation of cultural tradition and biodiversity but also for community health care and drug development. In this study, medicinal plants refer to traditional medicinal plants used to maintain health and treat illnesses, which are used for more than a generation by the informants or may have the knowledge passed to them through time by their ancestors. There were initiatives to explore the biodiversity of Mt. Arayat. Bagunu et al. [13] documented in their unpublished terminal report 77 species of vascular plants in the northwestern slope of Mt. Arayat; 7 species of the Grass Family, 16 families of forest trees, 9 Orchid families, 18 fern species and 75 mushroom species. Follow up researches were undertaken for more detailed identification of plants available in Mt. Arayat covering important aspects of their potentials for health, medicines and food sources. Abille [14] in her inventory of BS Biology researches of natural products-related from 2001 to 2015 found that phytochemical studies had the highest percentage, followed by antimicrobial (anti-bacterial and anti-fungi) studies and cytotoxicity studies the least. Anent to these studies are the revelations of folk healers that they use some of these plants for treating illnesses and diseases as mentioned in an unpublished report of Espiritu[15] where 55 medicinal plants were identified specifically of their medicinal contributions based on local names. However, the quantitative analysis of the data was a bit explored. Ong and Kim[16] mentioned only one conducted quantitative ethnobotany study by Abe and Ohtani in 2012 in the Philippines in his review of related literature and none so far in Central Luzon. Hence, this study serves as springboard for the understanding of the relative cultural importance of these medicinal plant studied in Mt. Arayat, Pampanga, Philippines and thus support communities to manage their resources more effeftively or finding plants that maybe useful to the community for medical or other purposes. Consistent with R ; D priorities of the agenda thrust of the Department of Science and Technology (DOST) for 2011-2016 to address the identified pressing health problems of the Filipino people by the Department of Health (DOH), the study is aligned with the National Unified Health Research Agenda (NUHRA) towards drug discovery from natural and indigenous sources through ethnobotany. Thus, the documentation of the traditional uses of plants particularly for medicinal value is an urgent matter for preserving the knowledge and providing baseline data for future pharmacological and phytochemical studies and natural product development, which are valuable in healthcare. How to cite What is Ethnobotany, Papers