William Shakespeare and the Renaissance Period Essay

Effect of Concentration on the Rate of Reaction Essay Example

Effect of Concentration on the Rate of Reaction Essay Example Effect of Concentration on the Rate of Reaction Paper Effect of Concentration on the Rate of Reaction Paper Introduction: In this experiment, we utilized the ability for the iodide ion to become oxidized by the persulphate ion. Our general reaction can be described as: (NH4)2S2O8 + 2KI A I2 + (NH4)2SO4 + K2SO4 (1a) However, we know that in an aqueous solution, all of these compounds except iodine will dissociate into their ionic components. Thus we can rewrite the equation in a more convenient manner: S2O82- + 2I- A I2 + 2SO42- (1b) It is important however to note that the NH4 and K ions are still in the solution, they are just unreactive. In order to measure the rate of the reaction, the conventional method would be to measure the species in question at certain times. However, this would be inconvenient, especially for a three hour laboratory period. Since the iodide ion can be oxidized by the persulphate ion, we can use sodium thiosulphate to be an indicator of the presence of iodine in the solution. For this experiment, we can simply calculate the rate of the reaction by timing the amount of iodine being produced in several runs. The reaction between iodine and sodium persulphate can be depicted as: I2 + 2Na2S2O3 A 2NaI + Na2S4O6 (2a) Similarly, this reaction above can also be simplified due to dissociation of all the ions except for iodine and persulphate. I2 + 2S2O3 A 2I- + S4O62- (2b) An interesting property of reaction (1) is that it produces a brilliant violet colour. However, this violet colour only results in the presence of iodine, or in other words, when iodine is being produced in the reaction. If sodium thiosulphate is added to reaction (1), than as long as there are two moles of thiosulphate for every mole of iodine, the solution will be colourless because the iodine is being used up in reaction (2). However, as time passes, the thiosulphate must run out at some point, and when it does, the violet colour will appear. Timing how long it takes for the violet colour to appear will allow us to calculate the rate of the reaction. In this experiment, 5 mL was also added in order to provide a more accurate measure of the time at which the colour first appears. Starch is helpful because it forms a blue complex with free iodine. Once we have the time elapsed for each run, we can calculate the rate of the reaction by applying the equation: Rate = -a  S2O8-2 / a  t The change in S2O8-2 is simply half the concentration of S2O3-2 because in reaction (2), the consumption of iodine and persulphate has a 1:2 ratio. Thus, the consumption of iodine can be seen as half the consumption of persulphate (S2O3-2). After calculating the rate of the reaction, the rate constant can be found by using the equation: Rate = k [ S2O82-]m[I-] n By comparing 2 sets of data at a time from 2 different runs, the order exponents m and n can be calculated, and thus, we can write the rate law for the iodide-persulphate reaction. We should also expect that the expected relationships between the concentration of S2O8-2 and the rate of reaction and rate constant might not always be extremely accurate in this experiment. When dealing with ions, we must always consider the ionic strength of the ions involved. The rate of the reaction will increase as the ionic strength gets stronger, thus, we will not always see a perfect linear relationship between [S2O8-2] and the rate of the reaction and the rate constant. The purpose of this experiment was to perform many trials of the same experiment, varying only the concentrations of certain ionic compounds in order to determine the affect of concentration on the rate of a reaction. By varying the concentration of different compounds for each run while keeping other factors constant, we were able to obtain experimental data that would give us a relationship between concentration and reaction rate.

Human Rights and English Law Essay Example | Topics and Well Written Essays - 1250 words

Human Rights and English Law - Essay Example As the paper declares our formulation of the function of the criminal law so far as it concerns the subject of this inquiry . . . is to preserve public order and decency, to protect the citizen from what is offensive or injurious, and to provide sufficient safeguards against exploitation and corruption of others, particularly those who are specially vulnerable because they are young, weak in body or mind, inexperienced, or in a state of special physical, official or economic dependence. It is not, in our view, the function of the law to intervene in the private lives of citizens, or to seek to enforce any particular patter of behaviour, further than is necessary to carry out the purposes we have outlined. From this paper it is clear that the committee report sparked the furious Devlin4-Hart5 debate and educated the public of the need for open-mindedness and clarity of reasoning resulting on the clarification of the problems or issues of homosexuality and prostitution, clearly positivist inputs. What previously has been the undoubted mechanism to enforce social morality, criminal law is being hedged out from private behaviour that does not harm other people; a concept that derived its roots from JS Mill's harm principle. The committee recommendation that "homosexual behaviour between consenting adults in private should no longer be a criminal offence," specifically between men over the age of 21, except in the armed forces, led to the passage of the 1967 Sexual Offences Act which replaced the 1861 Offences against Persons Act, the previous law against homosexuality and paved the way to legalizing homosexuality except for some homosexual acts. The age of consent for homosexual men was reduced in 1994 to 18 and in 2001 to 16 while homosexual acts in the armed forces were decriminalised. In May 2003 the Sexual Offences Act 2003 came into force, repealing the sexual offences of buggery and gross indecency and criminalised sexual behaviour that a person knew or ought to have known was likely to cause distress, alarm or offence to others in a public place, including sexual activity in public cruising and 'dogging' areas. The new act consolidated five previous statutes, particularly the Criminal Law Amendm ent Act 1885, Vagrants Act 1898, Incest Act 1908, Criminal Amendment Act 1912, and Criminal Amendment Act 1922 and further driven by public concern over children. The 1885 act repealed the Contagious Diseases Acts (1864, 1866 and 1869) directed against prostitution.