• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Determining activation energy (Ea) of a reaction potassium between peroxodisulphate and iodine

Extracts from this document...

Introduction

Ho Ka Wing (9) Group: 3 Date: 09-11-09 Determining activation energy (Ea) of a reaction potassium between peroxodisulphate and iodine Objective To determine the activation energy for the reduction of peroxodisulphate(VI)ions. S2O82- (aq) by iodide ions I- , using 'clock reaction'. Theory Activation Energy (Ea)-The minimum amount of energy required to start a reaction. A certain amount of activation must be supplied to initiating a reaction (even if the reaction is exothermic) because this energy must be absorbed to weaken or even break the bond holding the atoms in the reactant particles before the bond formation. The activation energy is used to overcome the energy barrier in the reaction. If the reactants do not gain energy that is greater or equal to the activation energy, the reaction won't occur. The equation for the reduction of peroxodisulphate(VI)ions by iodide ions : S2O82- (aq)+2I-(aq) -> 2SO42-(aq) +I2(aq) The equation of the reaction between thiosulphate ions and iodine formed in the above equation: 2S2O32-(aq) +I2 (aq) ->S4O62-(aq) +2I-(aq) Controlled Variables: 1. Concentration of potassium peroxodisulphate(VI)solution, potassium iodide solution,sodium thiosulphate solution and starch solution 2. Volume of potassium peroxodisulphate(VI)solution, potassium iodide solution, sodium thiosulphate solution and starch solution Dependent variable: - Time taken for the appearance of the blue-black color of the iodine-starch complex Independent variables: -temperature of the mixture Small amount Na2S2O3of is used to restrict the main reaction (the first reaction) ...read more.

Middle

skin contact * May cause sensitization by inhalation Sodium Thiosulphate - Na2S2O3 General Hazards * Irritant * Irritating to eyes, skin and repository system Potassium Peroxodisulphate - K2S2O8 General Hazards * Harmful * May cause sensitization by skin contact * May cause sensitization by inhalation Special Handling Information * Eye protection (safety goggles) must be worn at all times. * Wear gloves * Avoid skin contact with the chemicals Procedures: 1. the beaker was half-filled with water and heated to between 49? and 51?.This would be used as a water-bath. 2. Burette was used to measure the volume of 10.00 cm3 potassium peroxodisulphate(VI)solution into the first boiling-tube. The first tube was clamped in the water-bath and a thermometer was placed in the solution in the first boiling tube 3. Burette was used to measure the volume of 5.00 cm3 for both potassium iodide and sodium thiosulphate solutions and the volume of 2.5 cm3 starch solution into the second boiling tube. The second tube was clamped in the water-bath and a thermometer was placed in the solution in the second boiling tube 4.When the temperatures of the two solution were equal and constant(to within�1?), the contents of the second boiling-tube was poured into the first one, shake to mix, and the clock was started. ...read more.

Conclusion

Higher the temperature, higher the rate of reaction whereas higher the activation energy, lower the reaction rate. However, a rise in temperature has a more significant effect on the reactions with high activation energy. Temperature usually has a major effect on the rate of a chemical reaction. Molecules at a higher temperature have more thermal energy. Although collision frequency is greater at higher temperatures, this alone contributes only a very small proportion to the increase in rate of reaction. If we increase the temperature from 300 K to 310 K then the average speed increases by a factor of (310/300)1/2 is about 1.016 which is an increase of 1.6%. However the rate usually increases by 200%-300%. The effect of increasing collision frequency on the rate of the reaction is very minor. Much more important is the fact that the proportion of reactant molecules with sufficient energy to react (energy greater than activation energy: E > Ea) is significantly higher.The distribution curves below in diagram 1 for 300 K and 310 K with energy greater than 52kJ mol-1 shows what happens to the rate. (Diagram 1: Enthalpy Profiles) As can be seen in the graph a higher proportion of molecules have enough energy to react. Reference Textbook ( New Way Chemistry for Hong Kong A-level) Study guide Website ( www.wikipedia.org) ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Physical Chemistry section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Physical Chemistry essays

  1. Investigating the rate of reaction between peroxydisulphate(VI) ions and iodide ions

    The rate equation A rate equation can be written for any reaction, as long as an experiment is carried out to find how the rate depends on the concentration of the reactants. For the general reaction in which A and B refer to the reactants: The rate equation is: n

  2. Investigating how concentration affects rate of reaction

    I believe this will help me in obtaining accurate results. Temperature of Reactants (�C) Time Take For the Mixture to Turn Colourless (seconds) 10 101.5 20 23.7 30 10.2 40 5.1 50 1.9 60 0.8 I also conducted a pre-test to trial my method for investigating how temperature change affects the reaction rate.

  1. The Determination of rate equation

    detect an anomalous, as it's difficult to detect a trend using less data. To increase the reliability of the collected data I will repeat the experiment for each different concentration 3 times, as it will reduce errors caused during the experiment.

  2. Investigating the Rate of the Reaction between Bromide and Bromate Ions in Acid Solution

    If the reaction is found to be xth order with respect to A and yth order with respect to y, then: (Equation 1.5.3) The rate equation can be derived from this: (Equation 1.5.4) where k is the rate constant for the reaction.

  1. The position of different metals in the reactivity series and their effect on activation ...

    The value of lnA shall be expressed with an accuracy of two decimal places. l My other method is to react different metals with dilute HCl and then quench reaction by removing the metal and titrate with a standard solution that I will make.

  2. detremining the rate equation

    From my results I will plot 2 separate graphs for rate against concentration. One is for when I vary the concentration of Na2S2O3 and the other is when I will be varying the concentration of HCl. and from the shape of the graphs I will determine the order of the reaction.

  1. Determining the Order of Reaction: With Respect to Potassium Iodide

    that I have proved the rate equation experimentally, I want to find a value for the constant, 'k'. This is called the rate constant and its value remains the same when concentrations are changed. Using my results I should be able to calculate a value for 'k'.

  2. Individual investigation - Reaction to be studied Rate of reaction between propanone and ...

    > To make experiment accurate, we have to rinse the burette or pipette with the solution with the solution that we are going to use. > When titrating, we have to perform certain process show below: * Use accurate grading pipette into the conical flask.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work