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Calculating the Results for Using the Iodine Clock Method to Find the Order of a Reaction (Activity EP6.4)

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Presentation on theme: "Calculating the Results for Using the Iodine Clock Method to Find the Order of a Reaction (Activity EP6.4)"— Presentation transcript:

1 Calculating the Results for Using the Iodine Clock Method to Find the Order of a Reaction (Activity EP6.4)

2 The following series of steps is required to complete the calculations The following series of steps is required to complete the calculations Calculating the concentration of [I - ] in the 5 reaction mixtures: Calculating the concentration of [I - ] in the 5 reaction mixtures: Mixture 1: [I - ] = Volume of KI x [KI] Mixture 1: [I - ] = Volume of KI x [KI] Total volume of mixture Total volume of mixture = 5.0 x = 0.5 mol dm -3 For the other mixtures substitute the appropriate volumes into the above equation

3 Reactant in excess (part c) The number of mol of I - in mixture 5 is calculated as follows: The number of mol of I - in mixture 5 is calculated as follows: Concentration = volume of KI x [KI] = 1 x 1.0 = 0.1 mol dm -3 Total volume of mixture 10 Total volume of mixture 10 The [S 2 O 8 2-] in mixture 5 is calculated as follows: The [S 2 O 8 2-] in mixture 5 is calculated as follows: Concentration = volume of K 2 S 2 O 8 x [K 2 S 2 O 8 ] = 2 x 0.04 Total volume of mixture 10 Total volume of mixture 10 = 8 x mol dm -3 = 8 x mol dm -3 The calculation shows that I - is in excess. Why is mixture 5 used? It is used because it contains the lowest [KI] used and this can be easily compared to [K 2 S 2 O 8 ] which is kept constant in all reaction mixtures

4 Total amount of iodine produced (part d) This is calculated from the reaction between peroxodisulphate(VI) ions and iodide ions. The reaction for this is: This is calculated from the reaction between peroxodisulphate(VI) ions and iodide ions. The reaction for this is: S 2 O 8 2- (aq) + 2I - (aq)2SO 4 2- (aq) + I 2 (aq) The total moles of iodine produced is calculated as: [ K 2 S 2 O 8 ] x Total volume of mixture [ K 2 S 2 O 8 ] x Total volume of mixture = 8 x x = 8 x moles I 2 can be produced

5 The amount in moles of thiosulphate ions added to each mixture (part e i) This is calculated as : This is calculated as : [Na 2 S 2 O 3 ] x volume added [Na 2 S 2 O 3 ] x volume added = 0.01 X = 2 x moles

6 The amount of iodine used up by thiosulphate ions (part e ii) The reaction is: The reaction is: 2S 2 O 3 2- (aq) + I 2 (aq) S 4 O 6 2- (aq) + 2I - (aq) In the reaction 2 moles thiosulphate ions react with 1 mole of iodine. The reaction is 2:1 and the moles of iodine used up is calculated to be: 1 x moles 1 x moles

7 The percentage of the reaction studied (part e iii) This is calculated as follows: % Reaction studied = Moles of iodine used x 100 Moles of iodine made Moles of iodine made = 1 x x x x = 12.5%

8 Calculating the initial rate The can be calculated for each mixture as follows: The can be calculated for each mixture as follows: Rate = The number of moles of iodine used Rate = The number of moles of iodine used Time taken for colour to appear (T) Time taken for colour to appear (T)Or 1 x T

9 Tabulating the results Mixture [I - ] Clock time (s)Rate Mol dm -3 s -1 Temp°C


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