Sodium Thiosulphate and Hydrochloric Acid Coursework Essay Example for Free

Sodium Thiosulphate and Hydrochloric Acid Coursework Essay In this experiment I will be seeing how the concentration of Sodium Thiosulphate, Na2S2O3, and Hydrochloric Acid, HCl, affects the rate of the reaction. In this reaction the solution turns milky yellow as sulphate is displaced and forms a solid precipitate. Na2S2O3 (aq) + 2HCl (aq) - 2NaCl (aq) + H2O (l) + SO2 (aq) + S (s) The Rate of a reaction can be represented as: ?concentration and so is the time ? time taken for the reactants to be used up. Therefore I will be investigating if either: Rate ? [Na2S2O3]x or/and Rate ? [HCL]Y where X and Y are the orders of the reaction. To calculate the rate equation and orders of the reaction I am going to use the log function: As Rate ? [Na2S2O3]x and Rate ? [HCL]Y Rate = k1 à ¯Ã‚ ¿Ã‚ ½ [Na2S2O3]x Rate = k2 à ¯Ã‚ ¿Ã‚ ½ [HCl]Y Take logs logRate = logk1 + X log[Na2S2O3] logRate = logk2 + Y log[HCl] eq. of line Y = C + M X Y = C + M X This shows how the power, and order of the reaction, can be found by drawing a graph of logRate against log[concentration] and the gradient of the line will give the order of the reaction. The two equations can then put together to give an overall rate equation: Rate = k à ¯Ã‚ ¿Ã‚ ½ [Na2S2O3]x[HCl]Y Experimentally I will be changing the concentrations of each the reactants independently and then calculating the rate for each concentration. From these rates I will be able to draw a log graph of rate against concentrations and from my calculation I can find the orders for each of the reactants. Variables The independent variable in the experiment is the initial concentrations of Sodium Thiosulphate and Hydrochloric Acid. I will be changing this variable and seeing how it affect the time taken for the reaction to take place and therefore how the concentration affects the rate of the reaction. However as only one variable can be changed I will keep one reactant constant whilst changing the other to get a fair set of results. This will show me the affect of each reactant on the rate independently. The dependent variable is the one that will be monitored in the reaction. The dependent variable is the time taken for the reaction to take place which can be used to calculate the rate of the reaction. The method I will be using is by seeing how long it takes for a black cross underneath the conical flask to disappear which will be the point in all the reactions where the concentration of the sulphur precipitate is equal and so will the rate can be fairly calculated. To reduce errors I will need to use my preliminary results to find a volume that will give a long enough time to measure accurately, but not too long to affect the rate which is calculated by dividing initial concentration by time. These graphs show how if the time taken for the reaction to reach a specific concentration is too long it will not be a true reflection on the actual initial rate of the reaction. The first variable that must be controlled is the temperature of the reactions. This is because temperature will affect the rate of the reaction as a higher temperature will cause an increase in the rate. If the temperature varies between reactions it will have an affect on the results. To try and insure the same temperature is used I will have all reactants at room temperature and carry out all the reactions in one lesson. Another control is the the volume of reactants used and the depth of the solution. If this is changed the amount of precipitate that will need to be observed through will change and therefore the concentration at which the cross disappears will be different. To control this the same volumes will be used and the same conical flask will be used and therefore the depth will be the same. Similarly the cross used will need to be the same as a thicker cross would mean it will disappear at a different concentration of sulphur and the results will not be fair. Finally I w ill not shake or move the conical flask once the reactants have been put together as this again might affect the rate of the reaction. Equipment 1. 200cm3 of Na2S2O3 1. 200cm3 of HCl 2. 10 x 50cm3 beakers 3. 2 x Graduated Pipettes 4. Conical Flask 5. Stopwatch Method 1. Start by making the concentrations, using a graduated pipette measure out the correct volumes of Sodium Thiosulphate and put into 5 small 50cm3 beakers. Then add the corresponding amounts of distilled water and label with the correct concentration. 2. Secondly draw a black cross onto a piece of paper which is no bigger than the base of the conical flask, place the conical flask on top of the flask. 3. Using another graduated pipette, place 25cm3 of 2M hydrochloric acid into the bottom of the conical flask. 4. Whilst standing above the conical flask, looking directly down, simultaneously pour the first concentration of Na2S2O3 into the conical flash and start the stopwatch. 5. Keep observing and when the yellow precipitate causes the cross to completely disappear stop the stopwatch. 6. Record the time taken, wash out the conical flask thoroughly and repeat from step 3 but using the next dilution until all the concentrations have been reacted and recorded. 7. Repeat all results and average times. 8. Secondly replace the Sodium Thiosulphate with the HCl and copy above steps by measuring out correct concentrations and place into 5 more 50cm3 beakers. 9. This time add 25cm3 of Na2S2O3 into the bottom of the conical flask before recording the time taken for the cross to disappear again, for all the concentrations. 10. Repeat all results again for HCl concentrations. Initial Rates can then be calculated. Dilution Tables Na2S2O3 Concentration / moldm-3 Na2S2O3 (1M) / cm3 Distilled Water / cm3 1.0 20 0 0.8 16 4 0.6 12 8 0.4 8 12 0.2 4 16 HCl Concentration / moldm-3 HCl (2M) / cm3 Distilled Water / cm3 2.0 20 0 1.6 16 4 1.2 12 8 0.8 8 12 0.4 4 16 Safety Points As concentrated Hydrochloric acid will be used make sure eye and hand protection is worn. In case of contact, immediately flush skin with plenty of water for at least 15 minutes and with eye contact get medical attention immediately. Sulphur is also present so make sure the room is well ventilated to allow fumes to escape. Take care with glass wear, such as pipettes as they are fragile and may break easily. If broken clear up all glass immediately. Time Taken for Cross to Disappear / s Concentration of Na2S2O3 / moldm-3 1 2 Average Rate / moldm -3 s -1 logRate / log moldm -3 s -1 logconc. / log moldm-3 1.0 9.21 9.46 9.34 0.107 -0.971 0.000 0.8 13.71 14.00 13.86 0.072 -1.142 -0.097 0.6 17.43 17.21 17.32 0.058 -1.237 -0.222 0.4 23.66 22.71 23.19 0.043 -1.367 -0.398 0.2 49.78 50.12 49.95 0.020 -1.699 -0.699 Time Taken for Cross to Disappear / s Concentration of HCl / moldm-3 1 2 Average Rate / moldm -3 s -1 2 7.25 9.47 8.36 0.120 1.6 9.03 9.09 9.06 0.110 1.2 8.88 8.76 8.86 0.113 0.8 9.09 8.42 8.76 0.113 0.4 9.37 8.67 9.02 0.111 Analysis After drawing a graph of logRate against logConcentration and using the calculations in my plan, the gradient of the line gave me a value of 0.957 which taking into account experimental error shows the order of the reaction of Sodium Thiosulphate is 1. Also when carrying out the investigation for how the rate changes with the concentration of HCl there is no noticeable change in rate when the concentration varies. Therefore I didnt draw a graph, as the table shows HCl concentration doesnt affect the rate of the reaction and must be zero order. I can therefore deduce that the rate equation for this reaction is: Rate ? [Na2S2O3]1 and Rate ? [HCL]0 Rate = C x [Na2S2O3] where C is a constant which is proportional to the rate constant. The reason why the actual rate constant, k, can be calculated is because in the experiments the change in concentration cannot be calculated. However this always the same value as it is the concentration at which the cross disappeared and therefore the rate was proportional to 1/time. The intercept of the graph is equal to logC, -1.02, therefore C = 10-1.02 = 0.095s -1. To conclude the results show that the rate of the reaction between Sodium Thiosulphate and Hydrochloric Acid is directly proportional to the concentration of Sodium Thiosulphate. This gives evidence to the mechanism of the reaction. In a most reactions the mechanism is not made up of one step but a series of intermediate stages where molecules form and break down. Each of these steps will have a rate which is due to how many molecules are colliding. For example if 2 molecules must collide to for one product the reaction will be 2nd order. However the overall order for the reaction cannot be calculated using the stoichiometry in the overall equation. This is because the rate is determined by the rate of the slowest step of the mechanism, known as the rate determining step. In this reaction although 2HCl molecules are needed for the reaction to take place; however from the kinetics that I found HCl has no effect on the rate and is zero order. Therefore the slowest step in this reaction is the breakdown of 1 Sodium Thiosulphate molecules as the reaction is 1st order. Evaluation I feel the results I obtained allowed me to draw a graph and come to valid conclusions and be confident about calculating the order and rate equation for this reaction. I didnt have any obvious anomalies from my graph however there are some variations that meant I couldnt calculate a rate of exactly 1. Also from my table of results for changing the concentration of HCl, where all the rates must be the same for difference concentrations, there is a anomaly with the 2.0moldm-3 concentration. A limitation of my procedure was the way in which the rate was calculated using the disappearing cross method. This involves human judgement rather than a qualitative value that can be used to calculated the rate. There will also be an accuracy issue as there is a reaction time in realising the cross has disappeared and stopping the stopwatch. Another limitation of the procedure at the start of the timing and I had to add the chemicals together and start the stopwatch. This again causes an error in the actual time period taken for the cross to disappear. Another error is in the variation of temperature. As well as environmental variations in temperature the reaction was exothermic and heat is produced. When the temperature increases the k constant will increase, this is because the molecules have more kinetic energy and there is a higher probability that they will collide and react. This means its is hard to control this factor which is affecting the rate of the reaction. There are also many accuracy errors caused by percentage error in measuring. There is a time error in the time taken when the cross disappears and the delay in stopping the time. When using the graduated there was an error of 0.05/20 = 0.25% error, human reaction time is about 0.2/9.34 = 2.1%. To reduce this error I would choose another method of measuring the rate. Instead of using the cross method I would use a light intensity machine that could measure the change in colour over a period of time and stop and start timing when it had reach a certain value. This quantitative method of measuring should make the results more accurate. To control the temperature I could use a large water bath which could control the temperature throughout the reaction. Another method that could be used is to measure the products formed. The easiest would be using a gas syringe to measure the amount of SO2 formed. This again would give a more quantitative results and increase the accuracy and reliability .

Criminal Justice System :: essays research papers

I do feel that they will be effecitve and in the next few pages I will explain why I feel this way and why I have taken this stand. First of all I read through the whole charter and as boring as it was I made it through unscaved. Just like anything in order to have something you need a purpose. A reason for doing something. The reason why this charter was brought forward was because that they realized that during that century millions of children, mean and women have been victims of unimaginable atrocities that deeply shock the conscience of humanity. That sounds like enough for me. When I read that, I was think â€Å"Oh my God†, I mean come on unimaginable atrocities. It is obvious that something that to be done and even the littlest change would make a difference. The first thing they did was establish a â€Å"Court†. This court was permanent and had the power to exercise its jurisdiction over people for the most serious crimes. What I like about this and a reason why I feel it will work also is that in the beginning of the charter is that they have a relationship with the United Nations. This relationship only makes this court stronger. Part III of the charter looks a lot like a military code of justice. It set’s principles to be followed by the court or in the military a Commander if you will. It appears to me that this charters strength is in Part III, because here is where all the rules or articles are that explain what can be done by the court and what can not be done. It breaks it down to the core, including what to do with someone under 18 years of age. I feel that this is where the strength of the court lies. It defines who is a criminal and who is not, it tells us when the court can pursue a criminal or when a crime is not comitted. The further I got into the parts, the more I strongly I feel about saying they will be effective. It seems as if this court is no different then another court we have in the USA. Part four set’s up the membership. It states who is in charge of what and what their responsibilites should be. When you have people who know what they are supposed to do and that they are held accountable to their jobs then failure is not an option.

Cooperative Learning Is Defined As An Interdependent Group Education Essay

Dahley ( 1994 ) identifies classroom needs that advance a comfy concerted acquisition environment in schools. Using the concerted acquisition scheme increases pupil accomplishment, societal accomplishments, post-school success, and the use of resources. Research supports this scheme as an engaging environment for the scholar ensuing in higher academic accomplishment and self-pride in pupils. This in bend increases the overall satisfaction of larning in pupils and promotes the desire to accomplish, every bit good as creates practical accomplishments needed in the concern universe. Johnson & A ; Johnson ( n.d. ) advocate the usage of concerted acquisition in any type of course of study that group work is executable. The standards for effectual execution in any schoolroom include the alteration of bing resources as one of the foundations for this scheme. Furthermore, the instructor is required to understand the demands environing the course of study, capable, and pupils. This will let for the appraisal of effectual heterogenous grouping constructions within the schoolroom. There are five indispensable constituents presented for instructors to see when organizing concerted acquisition groups. The first is group size. Small groups of two to five are most effectual, particularly with heterogenous grouping. The 2nd constituent is group map. Functionality of a group involves coaction, job resolution, treatments, brainstorming, and sharing resources to get at a reciprocally good finish. Another of import facet is group norms, which are cultivated over clip by making t he groups and keeping them to the criterions of mutuality for accomplishment. Next, group accomplishments are required to be taught throughout the procedure. Teaching and reenforcing the coveted accomplishments of teamwork, back uping others in the group, credence, positive interactions, and struggle declaration will non merely assist the pupils understand what is expected of them in their groups, but these accomplishments besides transfer to other countries such as the schoolroom, school, and community. Finally, ends and regulations are to be communicated clearly to the pupils. This is of import for group building every bit good as the activities the groups must carry through together. Kagan ( 1994 ) focuses on prosecuting mutuality that involves all pupils hand in glove and non competitively. Grouping should be structured to profit all group members every bit and use the different strengths of each member to counterbalance for any lacks. When instructors create a concerted acquisition environment to show lesson stuff to carefully selected heterogenous groups, the cooperation of pupils will increase and competitory behaviours become diminished. Even though competition is a normal behaviour exhibited by pupils, inordinate usage of competition can sabotage accomplishment in the schoolroom. Cooperation does non exhibit this quality. It enhances larning by making a structured acquisition environment that requires the pupil to be an active participant in the acquisition procedure, as opposed to a inactive perceiver in a schoolroom. Reducing competition in the schoolroom besides provides an chance for ELL pupils to take hazards they usually would non. Concerted acquisiti on is motivational for ELL pupils as it gives multiple positions within the group, it leads to deeper apprehension of the stuff, and it allows them to build cognition by detecting other pupils using higher-level thought ( Colorado, 2007 ) . The effectual execution of concerted acquisition entails five elements. The first component, positive mutuality, ensures the trust on each group member to finish the undertakings. Face-to-face interaction is the 2nd, and it requires each group member to interact personally with each member in a positive mode. Following, the answerability of each group member assures that the 3rd component of single engagement is met. The 4th, societal accomplishments, builds the environment for larning the necessary accomplishments throughout the interactions of the group every bit good as heightening accomplishments brought in from the members. Finally, group processing assesses the group through the positive and negative sentiments of the group members ( Dahley, 1994, Johnson & A ; Johnson, n.d. , Kagan, 1994 ) . The fortunes that allow for the usage of this scheme are illimitable. From pre-school to high school, the group interaction creates an mutuality that promotes socially responsible behaviour and increased accomplishment. When this attack is used to better linguistic communication accomplishments, the pupils have the ability to believe at a higher degree, hear and discourse the sentiments of other pupils, and associate the stuff to their lives in a more echt manner. An illustration of an activity affecting this scheme is the Think-Pair-Share activity ( Kagan, 1994 ) . The pupils begin by working separately on the inquiries that are given for a specific subject, such as designation and comparing of characters in a book the category is reading. After about 10 proceedingss, the pupils are grouped in braces where they discuss the replies to their inquiries with each other. After about five proceedingss, the braces so portion their replies with other squads or the whole group. This scheme h elps ELL pupils communicate what they are believing to a schoolmate in a less baleful environment and acquire the position of other pupils. Concerted grouping has many different attacks. Groups can be little as braces or big as required to run into the aims of the instructional activity. Ideally, they should incorporate three to five heterogenous pupils for the bulk of activities assigned. Homogeneous grouping, or ability grouping, can hold some benefits but is by and large best to be used meagerly, particularly with ELL pupils. Grouping ELL pupils homogeneously will non let for linguistic communication growing, as they will non hold entree to the equal patterning necessary to increase their linguistic communication accomplishments. Randomly puting pupils in groups can be effectual every bit long as all groups can run into the instructional ends of the activity, and there is a low incidence of ELL pupils in the schoolroom. Effective arrangement in heterogenous groups requires instructors to be cognizant of the ability degrees and societal accomplishments of the pupils in order to fit up complimentary accomplishments. Concerted grouping used to assist pupils with written look helps pupils derive experience by working through the authorship procedure. This is particularly good to ELL pupils. The instructor can make assorted ability groups where the stronger authors are able to assist the weaker 1s. Groups can be created to get down the authorship procedure with prewriting, which calls for brainstorming subject thoughts. All pupils can easy lend to this measure. After pupils have selected a subject, they can compose their rough bill of exchange in braces. When it is clip for alteration and redaction, group members take bends reading the documents and adding remarks, inquiries, or corrections as needed until the concluding bill of exchange is completed. This gives pupils the experience of reading the documents of other pupils as the composing procedure unfolds and the chance to better their ain authorship accomplishments through equal ratings. Working in little groups can assist ELL pupils larn how to work together and convey out larning chances that may hold been missed by independent work entirely. When pupils have a clear common end to work toward they can utilize their accomplishments to assist each other learn ( Gootman, 2001 ) . By promoting effectual communicating between equals to work out jobs in a safe orderly environment, a instructor is promoting societal growing and acquisition every bit good as academic accomplishment. As pupils learn to interact efficaciously with other pupils, accepting and lending different thoughts from the group as a whole it non merely builds assurance in the pupil socially, it strengthens the sense of accomplishment in academic undertakings. For ELL pupils, this provides a safe acquisition environment for them to larn and spread out their cognitive linguistic communication accomplishments within a societal context. Using concerted larning groups non merely develops psychosocial accomplishments in a safe and controlled environment, but besides creates state of affairss for ELL pupils to develop their linguistic communication accomplishments through equal mold. Cooperative acquisition allows ELL pupils who may non understand a given assignment to acquire aid from equals who do. Most pupils enjoy group work, and when they work in groups it can be a manner to promote them to take part in a undertaking that may be otherwise disputing or hard for them. The drawback to this is that some pupils can merely let the others to make their work for them, but if the instructor is watching closely, it should be evident who is lending and who is non and the instructor can step in as needed. There is a high degree of pupil battle with concerted grouping. All of the pupils have a undertaking and actively concentrate on making their portion. They can utilize thoughts from each other to come up with a solution to their group job. Concerted behaviours occur when the pupils who are more knowing aid those who are fighting in order to finish the undertaking as a group. This allows ELL pupils to construct their linguistic communication accomplishments.

Has the No Child Left Behind Act of 2001 Been Successful

In every school in the United States has students that fall behind in classes or don’t get proper education for them to be taught effectively. The No Child Left Behind Act of 2001 was created to push students of all grade levels to keep up in their classes, homework and grades so they could become an idol citizen to society. Even though this act is supposed to keep students on the same page as others, research shows that isn’t the case; that students Adequate Yearly Progress (AYP) test scores are going down. The United States’ push of reaching state standards for public school systems has brought to attention that if these standards are not reached, teachers and school faculty will take the infliction. â€Å"The No Child Left Behind Act of 2001 wasn’t signed into law by President Bush until Jan. 8, 2002, was reauthorization of the Elementary and Secondary Education Act, the central federal law in pre-collegiate education† (No Child 1). 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