The Haber Process Essays - Industrial Gases, Equilibrium Chemistry

The Haber Process 1. The Haber Process During the first decade of the twentieth century the world-wide demand for ammonia for use in fertilisers (in the form of nitrates) and in the production of explosives for use in mining and warfare could only be satisfied on a large scale from deposits of guano in Chile (2). Though this deposit was of huge size (approximately five feet thick and 385 kilometres long) it represented a rapidly depleting resource when compared to world-wide demand. As a result of this there was much research into how ammonia could be produced from atmospheric nitrogen. The problem was eventually solved by Fritz Haber (1868 - 1934) in a process which came to be known as the Haber Process or the Haber - Bosch Process. Haber developed a method for synthesising ammonia utilising atmospheric nitrogen and had established the conditions for large scale synthesis of ammonia by 1909 and the process was handed over to Carl Bosch for industrial development (1). the reaction is a simple equilibrium reaction which occurs in gaseous state as follows; N2 (g) + 3H2 (g) = 2NH3 (g) heat of enthalpy = -92.6 kJ/mol In predicting how to obtain the highest yield from this reaction we must refer to Le Chatlier's Principle. This states that for an equilibrium reaction the equilibrium will work in the opposite direction to the conditions forced upon it. The conditions most pertinent to the above reaction are temperature and pressure. The pressure exerted by any gas or mixture of gasses in an enclosed space is directly proportional to the number of atoms or molecules of gas regardless of their size or molecular mass. Reference to the above reaction shows that, as the reaction moves to the right the number of molecules and hence the pressure decreases. Therefore the reaction moving to the right (i.e. towards the product required) is favoured by an increase in pressure. With regard to temperature, the reaction moving to the right is exothermic i.e. it gives off energy (in the form of heat). Therefore reference to Le Chatlier's Principle shows that the reaction to the right is favoured by low temperatures. However, when Haber placed the reactants together under these conditions it was shown that the rate of reaction was so slow as to render the process unfeasible as an industrial process. This is because of an unusually high activation energy. The activation energy of a reaction is the energy required by the reactants to achieve an intermediate state required before they form the products. In the case of the above reaction the intermediate state requires the dissociation of diatomic gaseous nitrogen. The triple bond found between two nitrogen atoms when they form diatomic nitrogen is amongst the strongest chemical bonds known. this leads to an extremely high activation energy. At extremely high temperature the nitrogen molecule will dissociate and so, as the temperature approaches this point the rate at which the reaction to the right occurs and therefore the speed with which equilibrium is reached increases rapidly. Unfortunately experimentation showed that, as temperature approached the point at which the speed of the reaction was sufficient to produce a viable reaction the amount of ammonia produced was so low that the reaction was still unfeasible on as an industrial process. Faced with this failure to find conditions suitable for an industrial process Haber began to experiment to find a catalyst that would facilitate the reaction. A catalyst is a substance that reduces the activation energy of a reaction, thus increasing the speed at which the reaction occurs, or in the case of equilibrium reactions the speed at which equilibrium is reached. After hundreds of experiments Haber discovered that a fast enough reaction with a high enough yield of ammonia would occur with a pressure between 200 and 400 atmospheres and at a temperature between 670K and 920K in the presence of a catalyst of iron (in the form of iron filings to increase its active surface area) plus a few percent of oxides of potassium and aluminium. This process was first demonstrated in 1909 and patented as the Haber Process in 1910 (3). Experiments aimed at finding the most efficient conditions for the reaction have since resulted in the process described by the flow diagram

Visual Web-Based User Manuals Essay Example

Visual Web Visual Web-Based User Manuals Essay Visual Web-Based User Manuals Essay Essay Topic: Web Visual Web-Based User Manuals Name: Course: Institution: Instructor: Date: Techniques Visual web-based user manuals are instructions or user guides on educational websites. Since innovation has enabled online learning, it is important for instructors to employ effective techniques by incorporating basic active learning principles in the website’s special features. The fundamental aspect in this regard is to develop learning objectives that will help the users to identify what they are required to know by the end of the course. Technical resources and pre-existing software must also be put into consideration in the development of an interactive user interface. The instructor should therefore ensure compatibility and convenience to enable easy access by the user and that more information is available. Effectiveness and interactivity is also enhanced by securing commitment of all users such as the students, faculty, administrators and development of portals to link all of them. The use of hyperlinks, online communication and multimedia are effective when lecture contents are integrated with them creatively. The creative use of slideshows, sound, texts and images should be moderated to avoid deviation from the learning objectives. They should also be aligned with instructional design. Hyperlinks will allow the user to navigate through the pages in the educational websites. Video and audio conferencing over the internet, online discussion, emails and chartrooms provide comprehensive online communication with an effective feedback system. The user can ask questions and clarify certain topics to gauge their degree of understanding. Instructors can enhance the leaning process by creating, simple, efficient and attractive web pages. They should also provide opportunities for self-assessm ent, learning that is problem based and self-directed. On implementation, hyperlinks and online communication should be verified and monitored periodically to prevent difficulty in accessing the web-based user manuals. Benefits and Challenges There are several benefits of providing web-based manuals. Multimedia and graphics incorporated in the web-based manuals makes them attractive to the users, hence motivates them to look through and understand. The inclusion of hyperlinks allows for easy and efficient navigation of the web pages. The user is able to access more information on the particular course if techniques of online communication, hyperlinks and multimedia are applied with precision. Visual web-based manuals also have an advantage of larger space for sufficient packaging as compared to paper manual and they reduce tediousness. Challenges include difficulty in using the manuals among some learners, incompatibility with different web browsers and development of effective navigation through hyperlinks. If the user does not have online connectivity, he or she cannot access the manual. Therefore a paper manual must be produced along with the web-based manual and this increases costs.