Solubility and K Dependence on Temperature

Solubility and K Dependence on Temperature An exothermic reaction is one which has a negative ΔH value while an endothermic reaction is one which has a positive ΔH value. Based on the results, the dissolution of potassium hydrogen tartrate has a ΔHÂ ° value of 3.89 *104. Therefore as 3.89 *104 > 0, the dissolution of potassium hydrogen tartrate is endothermic, i.e. heat must be added to dissolve the salt in water. This is further supported by the negatively sloped graph above. It can be inferred from the graph that the higher the temperature, the greater the solubility of potassium hydrogen tartrate. The spontaneity of a reaction depends on the change in enthalpy (ΔH) and entropy (ΔS), as well as on the absolute temperature. The change in the Gibbs free energy (ΔG) can be used to determine if a reaction is spontaneous or not. Represented by the equation ΔGÂ ° = ΔHÂ ° TΔSÂ °, when ΔG is negative, a process proceeds spontaneously in the forward direction. When ΔG is positive, the process proceeds spontaneously in reverse. When ΔG is zero, the process is in equilibrium, with no net change taking place over time. Therefore as the ΔGÂ ° calculated at both 10.0Â °C and 50.0Â °C are positive, it can be deduced that the dissolution of potassium hydrogen tartrate is non-spontaneous in the forward direction at the temperatures tested (10.0Â °C to 50.0Â °C). The process however proceeds spontaneously in reverse at the mentioned temperatures. In fact, based on the results, the dissolution will only be spontaneous at 513.6K (ΔHÂ ° / ΔSÂ °) and above. Although both entropy and enthalpy are functions of temperature, this experiment assumes that ΔHÂ ° and ΔSÂ ° do not change significantly over the range of temperatures used. This assumption is valid over relatively small ranges. In this experiment, the various measurements occur within a small range of 40K. Therefore it is safe to assume that the values of ΔHÂ ° and ΔSÂ ° are relatively invariant over the small changes in temperature. Many reasons could cause the experimental value to disagree with the literature value. Probably the most significant source of error would be the inability to maintain the respective temperatures during the slow step of filtering the salt solution after heating/cooling. Gravity filtration was adopted in this experiment, and although the filter papers were fluted to encourage rapid filtration, the process still spanned several minutes. During this time, the temperature of the salt solution could have easily deviated from the desired temperatures towards room temperature. This could cause undesirable recrystallization/dissolution of the salt, thereby, affecting the molarity of the filtrate. This limitation could be overcome by using vacuum filtration to minimize such errors. Besides the possible undesirable recrystallization/dissolution before filtering was over, recrystallization could also occur in the filtrate before the 25mL aliquots were obtained. This would only apply to the samples that were experimented at temperatures above room temperature. As the filtrate cools, the salt would recrystalise, causing a change in homogeneity and molarity of the filtrate. Although the protocol was to immediately aliquot 25mL after filtration, the time for the filtrate to reach at least 25mL was sufficient enough for significant cooling of the solution, with the large surface area of the solution filtering dropwise and the contact with the cool conical flask. A possible solution to this problem is to heat the filtrate again after filtration before aliquoting to ensure all the salts that may have recrystalised dissolve. However, the heating should be gentle to prevent significant lost of solvent and prevent change in molarity. Another source of error would be the assumption that the molarity of the given NaOH solution is accurate. Alkaline solutions such as NaOH absorb carbon dioxide from the atmosphere according to the reaction: CO2 + 2OH- ↔ + CO32- + H2O. Since hydroxide ion is consumed by this reaction, the concentration of the sodium hydroxide solution will be changed. Therefore the precise concentration of the NaOH solution may not be the value that what was stated on the bottle, especially if the solution was prepared long before the experiment was conducted. Standardization of the NaOH solution should be done just before the experiment is conducted. Although in this experiment, the molarity of the provided NaOH solution was assumed to be accurate and no further standardization was done, precautions were taken to protect the solution from the carbon dioxide that is always present in the atmosphere. As during titration, the NaOH solution in the buret will be exposed to air, the buret used was prepared for use only when it was needed, and fresh sodium hydroxide should be added if it. The initial steps of the procedure was to obtain approximately 200ml of NaOH solution from the stock bottle. To obtain higher accuracy though, the NaOH taken from the stock bottle should not be more than what is needed for one titration. More NaOH solution should be taken from the stock bottle when needed. Other precautions were also taken during the experiment to reduce contamination. Apparatus were scrupulously cleaned and rinsed with solutions that they were to contain before use. The experiment was also cautiously done to prevent loss of material through spillage, splashing or splattering. Conclusion This experiment successfully demonstrated the relationships between state functions, including entropy and enthalpy, free energy, spontaneity, and equilibrium constants. Since ΔHÂ ° and ΔSÂ ° were both positive, the dissolution of potassium hydrogen tartrate was spontaneous at high temperatures. This means that the potassium hydrogen tartrate needed energy from the surroundings to dissolve. The reverse process however, is spontaneous. A significant percentage error was obtained by comparing of the obtained solubility product constant with the literature value. Although precautions were taken to ensure accuracy, such an error proves that solubility product constants are extremely difficult to obtain experimentally because of limitations of the experiment and the necessity to identify all chemical species and processes present in the chemical system used to obtain the values.

Exploring Teaching Methods that Help Engage Students Essay -- Educatio

Considering a stereotypical class room, the bell rings, students are almost in their seats, and the teacher is demanding their attention. It is hard for the teacher to gain the attention let alone the willingness to learn from their students. No matter what subject is being taught, this has the recipe for boredom from the get go. Any curiosity or imagination for the students has been choked. In order for the teacher to gain the eagerness to learn from his students, he would have to resort to all the mental keenness he could muster. No matter how gifted the teacher, students tend to lose interest in learning in an everyday run of the mill style of class room environment. What creative power or what unusual and highly innovated resource can be implemented into a classroom that has been limited by tradition, a lack of creativity, and monotony? The answer is not a teacher who has an ingenious nature or who is a skilled innovator. The answer relies on the teacher’s methods. There are many different methods that have proved to be effective. Activities such as group lead discussion, group discovery, and teacher lead critical thinking discussions have proved effective in integrating different learning styles (Chick). Another method that will stimulate the imagination, and arouse the analytical side of learners is implementation of audio visuals and visual aids for the introduction, during the lectures, prompts for discussions, and even for the closure of class (Atkinson 2). This is a tool – a resource that needs to be tapped. Lastly, setting up the classroom into groups of desks and even changing the classroom on a day to day basis that will emulate what kind of methods are being used for that day by the teacher keeps lear... ...ary Module. ProQuest. Grafton Library, Fredericksburg, Va. 17 Nov. 2008 Olson, Allan. . "Technology that MOVES Assessment and Student Achievement FORWARD. " MultiMedia & Internet@Schools 1 Nov. 2004: 26-28. Education Module. ProQuest. Grafton Library, Fredericksburg, VA. 13 Feb. 2009 Strassman, Barbara K., and Trisha O'Connell. "Authoring with video." The Reading Teacher 61.4 (Dec 2007): 330(4). General OneFile. Gale. LIRN. 3 Oct. 2008 . Teachable Moments. Morningside Center for Teaching Social Resposibilities. 13 Feb 2009 . Wong, Harry, and Rosemary Wong. How To Be An Effective Teacher: The First days of School Mountain View, CA: Harry K. Wong Publications, Inc, 2004.

My personal brand Essay

My personal brand is that I am super energetic in my job. When I was working as a sale assistance in a large retail store, I would always keep my mind that I need to be cheerful and energetic in doing my job, so the customers could feel my passion and caring. This can be help me to avoid those negative emotion and things, makes me to be more productive in work. I would think that is one of the most important strengths of my personal brand. Another strength is that I am willing to learn and communicate with others. Although I am not a fast learner, I will put more effort in order to achieve the result. Also, a good relationship with colleague would make all the things much easier. Therefore, I am energetic in communicating with others and having a connection with them. My weakness is that I am not a fast learner, but I am willing to learn. In order to strengthen my personal brand, there are several actions I could do. First of all, in order to have a good communication with others, language is the most important thing. Improving my English level could help me to have a better connection with others. Also, understand the history of Australia can help me to overcome the barriers of culture difference. Secondly, attending the networking events could help me to build a relationship with different employers. Thirdly, build a personal brand in ‘linked in’ website can help me to connect with others. Also, it can let others to understand who I am.

Principles of the Constitution Essay - 1057 Words

April 21, 2013 Principles of the Constitution POS 301 Part I: Principles of the Constitution | | DEFINITION | | Self-Government | A government in which the people who live in a place make laws for themselves. | In Massachusetts Bay, men who owned property could go to a town meeting and vote. | Separation of Powers | Power of the Constitution is divided among the three branches. | James Madison and the other authors of the Constitution created three branches to make sure that the government’s powers were limited. | Checks and Balances | A system that lets each branch limit the power of the other two. | No single branch or person had the power to run the United States alone. | The U.S. Constitution is the†¦show more content†¦Part II: The Three Branches of the Government | Legislative Branch Headed by Congress (Senate and House of Representatives) * Pass Laws * Originate Bills * Impeach officials * Approve treaties Executive Branch Headed by the president * Direct the government * Command the Armed Forces * Deal with international powers * Act as chief law enforcement officer * Veto laws Judicial Branch Headed by the Supreme Court * Interpret the Constitution * Review laws * Decide cases involving states’ rights Balance of Power Interaction/The ways each branch of the national government can check the power of the other two branches: The Supreme Court can declare a law passed by Congress unconstitutional The Supreme Court can declare the President’s actions unconstitutional The President chooses the judges for the national government’s courts The President approves or vetoes laws passed by Congress Congress must approve the judges the President chooses for the national court If two-thirds of the Senate and House agree, Congress can pass a law even if the president has vetoed it How a bill becomes a law: All of the laws in the United States begin as a bill, which must be approved by the Senate, House of Representatives, and the President. 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