Reaction Rate Constant Definition and Equation

The rate constant is a proportionality factor in the rate law of chemical kinetics that relates the molar concentration of reactants to reaction rate. It is also known as the reaction rate constant or reaction rate coefficient and is indicated in an equation by the letter k. Key Takeaways: Rate Constant The rate constant, k, is a proportionality constant that indicates the relationship between the molar concentration of reactants and the rate of a chemical reaction.The rate constant may be found experimentally, using the molar concentrations of the reactants and the order of reaction. Alternatively, it may be calculated using the Arrhenius equation.The units of the rate constant depend on the order of reaction.The rate constant isnt a true constant, since its value depends on temperature and other factors. Rate Constant Equation For a general chemical reaction: aA bB → cC dD the rate of the chemical reaction may be calculated as: Rate k[A]a[B]b Rearranging the terms, the rate constant is: rate constant (k) Rate / ([A]a[B]a) Here, k is the rate constant and [A] and [B] are the molar concentrations of the reactants A and B. The letters a and b represent the order of the reaction with respect to A and the order of the reaction with respect to b. Their values are determined experimentally. Together, they give the order of the reaction, n: a b n For example, if doubling the concentration of A doubles the reaction rate or quadrupling the concentration of A quadruples the reaction rate, then the reaction is first order with respect to A. The rate constant is: k Rate / [A] If you double the concentration of A and the reaction rate increases four times, the rate of the reaction is proportional to the square of the concentration of A. The reaction is second order with respect to A. k Rate / [A]2 Rate Constant From the Arrhenius Equation The rate constant may also be expressed using the Arrhenius equation: k Ae-Ea/RT Here, A is a constant for the frequency of particle collisions, Ea is the activation energy of the reaction, R is the universal gas constant, and T is the absolute temperature. From the Arrhenius equation, it is apparent that temperature is the main factor that affects the rate of a chemical reaction. Ideally, the rate constant accounts for all of the variables impacting reaction rate. Rate Constant Units The units of the rate constant depend on the order of reaction. In general, for a reaction with order a b, the units of the rate constant are mol1−(mn) ·L(mn)−1 ·s−1 For a zero order reaction, the rate constant has units molar per second (M/s) or mole per liter per second (mol ·L−1 ·s−1)For a first order reaction, the rate constant has units of per second of s-1For a second order reaction, the rate constant has units of liter per mole per second (L ·mol−1 ·s−1) or (M−1 ·s−1)For a third order reaction, the rate constant has units of liter squared per mole squares per second (L2 ·mol−2 ·s−1) or (M−2 ·s−1) Other Calculations and Simulations For higher order reactions or for dynamic chemical reactions, chemists apply a variety of molecular dynamics simulations using computer software. These methods include Divided Saddle Theory, the Bennett Chandler procedure, and Milestoning. Not a True Constant Despite its name, the rate constant isnt actually a constant. It only holds true at a constant temperature. Its affected by adding or changing a catalyst, changing the pressure, or even by stirring the chemicals. It doesnt apply if anything changes in a reaction besides the concentration of the reactants. Also, it doesnt work very well if a reaction contains large molecules at a high concentration because the Arrhenius equation assumes reactants are perfect spheres that perform ideal collisions. Sources Connors, Kenneth (1990).  Chemical Kinetics: The Study of Reaction Rates in Solution. John Wiley Sons. ISBN 978-0-471-72020-1.Daru, Jà ¡nos; Stirling, Andrà ¡s (2014). Divided Saddle Theory: A New Idea for Rate Constant Calculation. J. Chem. Theory Comput. 10 (3): 1121–1127. doi:10.1021/ct400970yIsaacs, Neil S. (1995). Section 2.8.3.  Physical Organic Chemistry  (2nd ed.). Harlow: Addison Wesley Longman. ISBN 9780582218635.IUPAC (1997)  Compendium of Chemical Terminology, 2nd ed. (the Gold Book).Laidler, K. J., Meiser, J.H. (1982).  Physical Chemistry. Benjamin/Cummings. ISBN 0-8053-5682-7.

Character Analysis Of Vicki-Tikki Tavi - 1727 Words

What motivates a person or character in text to undertake a mission. Rikki-Tikki-Tavi by Rudyard Kipling is a fictional narrative that demonstrates that characters in text undertake a mission because of multiple motivations. The narrative begins by introducing the reader to Rikki-Tikki-Tavi and the human family, as well as the initial conflict of Rikki-Tikki being washed away from his mongoose family and ends up being adopted by the human family. Soon thereafter, Rikki-Tikki encounters the story’s most important conflict, battling the snakes, and while engaging in his mission to kill the snakes, Rikki killed Karait the dusty brown snakeling, Rikki then engaged in battle with Nag and won, Rikki lastly slaughtered Nagaina. The resolution†¦show more content†¦An example of this from another text called David Copperfield by Charles Dickens is that when Steerforth shows protection and love for David that David quickly responds with loyalty and admiration which is like how Rikki Tikki responded to the family when they protected him. Yet another quote from the story that demonstrates that Rikki Tikki Tavi is motivated to destroy the snakes because he is giving love and protection back to the adoptive human family is when the text states, â€Å"They took him into the house, and a big man picked him up between his finger and thumb and said he was not dead but half choked. So they wrapped him in cotton wool, and warmed him over a little fire, and he opened his eyes and sneezed.† The 4 specific parts that show the family’s love are when they took him into the house, when the big mank held him, when they warmed him over a little fire, and when they wrapped him in cotton. When they took him into the house this shows love because only people with love in their heart will take a wild animal into their house, also when the Big man picked up Rikki this shows immense trust and love because he is willing to love and protect an animal that he h as just met, when the family wrap him in cotton and warm him over a little fire they show protection and love for Rikki because they have

Osce Scenarios Free Essays

OSCE Scenarios ONE You are a 72 year old lady. This morning you were hanging your freshly laundered curtains, when you suddenly felt dizzy and you remember nothing after that, until your friend was calling your name. You have no idea how you ended up on the floor. We will write a custom essay sample on Osce Scenarios or any similar topic only for you Order Now You have had a few dizzy spells No SOB or chest pain. You have the odd â€Å"missing heart beat† not too troublesome. Otherwise you are fit and well. You were not incontinent during the attack. TWO You are a 42 year old professional trombone player. You are rehearsing for a tour abroad. Last night you seemed OK just a bit tired and possibly had a bit of a fever. This morning you woke up with severe left sided chest pain aggravated by deep breathing and coughing. You are very frightened because your sister had a pulmonary embolism after the birth of her baby. There is no sputum or haemoptysis. You had slight asthma as a child. You haven’t got much of a cough, but feel SOB and frightened to breathe deeply. Your general health is good and you’ve had no serious illnesses in the past. THREE You are a 35 year old man who came to AE with pain when passing urine and discomfort for 3-4 days. You think that there was a little blood in your urine once. You are gay and not practice safe sex. (DO NOT VOLUNTEER THIS INFORMATION UNLESS YOU ARE ASKED. ) You are not particularly bothered about HIV. Generally your attitude is rather cavalier and have had several sexual partners in the past. FOUR You are the wife of an 82 year old man and you brought him into AE because you are frightened and worried about him. For the last 3-4 days he’s been increasingly confused and today he started to get verbally abusive. He has never had psychiatric problems. This is most unlike his normal self. He feels a bit hot to you and his urine has been a bit smelly. He has mild, diet controlled diabetes and â€Å"some prostate problem† otherwise he has been remarkably healthy. FIVE You are the father of a 3 year old girl. Your wife and you separated 2 years ago and she is the main carer for the child. You have her every other weekend. You are rather vague about the child’s health, mainly because she does not live with you. DO NOT VOLUNTEER THE FOLLOWING INFORMATION: You have been sexually abusing the girl for some time and obviously don’t want your ex-wife to find out, or anyone else for that matter. Therefore, you want this problem sorted out now. SIX You are a 72 year old heterosexual man. For the last few weeks you have noticed increasing difficulty with passing urine, terminal dribbling and a pressure feeling in your lower abdomen,. Your general health is fairly good but lately you have lost some weight and you’ve become impotent. SEVEN You are the mother of a 3 year old boy. This afternoon he fell off the slide in the park (about 2m high). He was sick once about 5 minutes after the accident, he was NKOD but has complained of headache ever since. He is alert and had something to eat about half an hour ago which stayed down. You are worried about the effects of the injury and have no idea what to look out for. EIGHT You brought your 6 month old baby to AE as you are very anxious about her. She developed a cold, cough and temperature 3 days ago. She has not been eating well but she has no DV. This morning you noticed that she is covered in a rash from head to foot. She is up to date with her immunisations (BUT DO NOT VOLUNTEER THIS INFORMATION. ) In a nearby school there are three confirmed cases of measles. You are convinced that your child has meningitis and you know this can be a fatal illness. Therefore, you think she should be admitted to hospital. NINE You are a 30 year old unemployed man. You have been abusing a variety of drugs, including diazepam, dihydrocodeine, amphetamine and cocaine in the past. You have an agreement with your GP that he will prescribe 90 tablets of Diazepam 5mg a month. However, recently you have been quite agitated and been taking more than the prescribed dose. When you are broke for money you also sell some of your tablets on the black market. You came today asking the receptionist to reissue your prescription saying that the previous was stolen from you. You are determined not to leave until you get some more tablets. Anyway, you can’t see what all the fuss is about. A few more tablets are neither here nor there and you are fed up with these dragons, called receptionists. You decided to duff them up a bit! TEN You are the mother of a 12 year old boy. He fell and cut his knee this morning at school. You brought him to AE and after a long wait one of the junior doctors stitched his knee. The AE charge nurse checked that your son has not had a tetanus booster since he was 3 years old and informed you that he needs a booster today. You agreed to this. The young doctor proceeded to administer the injection that the nurse gave him. The young doctor was very friendly and nice to your son but appeared nervous with shaky hands. After he gave the jab he seemed very anxious and it transpired that it was the wrong injection. He hasn’t checked the vial before administering the vaccine. You are flabbergasted and furious and threaten to sue the hospital. ELEVEN You are a27 year old man from the Ivory Coast. You have been resident in the UK for 3 years and recently returned to your country for a family visit. As you lived in Africa most of your life you did not think it was important to take malaria precautions. You’ve been feverish and felt rotten for two days with the light hurting your eyes, your neck and back of your head and you have terrible griping pains in your upper abdomen on both sides. DO NOT VOLUNTEER THE INFORMATION THAT YOU HAVE JUST COME BACK FROM AFRICA! TWELVE You are a 29 year old woman who works as a solicitor in a big city law firm. This is a very prestigious job with high pressure and long working hours. Your main way of de-stressing is going to the gym at night. Two days ago your â€Å"back went† for the third time in six months and this morning you could hardly get out of bed and get dressed. The pain is really severe, especially when you bend down and at times like a knife in your back. You are not too bad at rest. The pain does radiate down your buttock to the back of your leg, but you have no pins and needles, loss of motor function or abnormal sensation. You are fed up and worried you might lose your job if you keep taking time off. One of your friends is a doctor and he told you that X rays are useless and you must have an MRI scan to see if you’ve got a slipped disc. You won’t budge unless the AE doctor agrees to do this. YOU WON’T BE FOBBED OFF! THIRTEEN You are a 58 year old Pakistani man,. You were diagnosed as a diabetic in 1999 and hypertensive in 2001. You take metformin, gliclazide and enalapril. Last week you came to the practice nurse for a blood test and this morning the practice receptionist rang you to say that you must come in to see the doctor to discuss the result of your recent blood test. You are really worried and think there is something horribly wrong. Your mother and aunt were both diabetic and died How to cite Osce Scenarios, Papers

New Beginnings free essay sample

Throughout my life, soccer has always been a huge part of my existence. Starting at the age of four I began to fiddle around with a soccer ball and learn to love the sport for what it was.I had always admired older girls for their sportsmanship and had hoped to be apart of that one day. I loved the feeling of scoring a goal and helping out my team. That thrill I had learned as a young child had stayed with me and was the ultimate driving force that caused me to keep continuing soccer and trying my hardest at it. When middle school rolled around soccer became more difficult to love. In the seventh grade I walked into school excited for the first day of soccer tryouts after school and couldn’t wait to see what it would entail. Until, the end of the day came and the realization hit me in the middle of tryouts that soccer was no longer a small thing you did for fun. We will write a custom essay sample on New Beginnings or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page It was a harsh game that you had to physically keep up with. Due to my lack of being in shape, I got cut from the seventh grade soccer team. I had never been so heart breakingly devastated in my entire life. I couldn’t grasp why it was that every girl I had played soccer with up till now had made the team except for myself. This is what drove my passion even more. I made a vow to myself that I would work hard and try again to make that soccer team the following year, and indeed I did. I spent my whole summer training for it and told myself over and over again I could do it, and I did. Soccer up until my junior was a blast. I had tried my hardest throughout the years to keep up physically and mentally with the game, but when we got a new coach my junior year, everything changed. I had to start all over again with earning my place on that team. No matter how hard I continued to try, my coach never played me. I went in once a game sometimes for a short duration of 5-7 minutes and then my time had been served and the game was over. This continued throughout the soccer season of my junior year and I tried my hardest to stay positive. When I went back to join the team my senior year, nothing had changed. I still continued to try my hardest, and get no explanation as to why I wasn’t playing when every other senior girl was. After countless of nights spent wallowing on the couch with my mom about how unfair I was being treated, I decided enough was enough. Growing up as a kid I would constantly hear from my parents: â€Å"Quitting is not an option.† This had always been my motto and I felt ashamed to think that I was quitting something. However, this is not considered quitting. Something in my life that I used to love, was causing me an abundance of stress and pain, to the point where I started evaluating my self-worth, I believe that it wasn’t worth sacrificing my self-esteem for. I look at myself leaving the soccer team my senior year as a step toward my future in a positive light. No longer, will I spend another night beating myself up on questioning why I wasn’t good enough. Through this experience I learned more about myself than I ever had before. I was able to focus more on my main interests such as writing and exploring. I truly am thankful for this experience and feel as if it was a necessary stepping stone towards my success in other fields. I most importantly learned that it is okay to put yourself first sometimes, and I overall gained a new self-worth.