Question

1. 10.00 mL of 0.200 M potassium iodide (KI) and 20.00 mL of 0.100 M ammonium persulphate ( (NH4)2S2O8) are added to a beaker containing 10.00 mL of 0.00500 M sodium thiosulphate (Na2S2O3) solution and starch indicator. Reactions shown in equations (1) and (6) take place and a purple colour appears after 23.43 seconds. a) Calculate the moles of thiosulphate ion (S2O3 2-) added to the reaction mixture. = 5.00 x 10^-5 mol of S2O3 2- b) According to equation (6), how many moles of thiosulphate are consumed for each mole of iodine (I2) formed in reaction (1) ? answer: 2 mol c) Therefore, how many moles of iodine were formed in the 23.43 seconds immediately following the mixing of the two reactants (potassium iodide and ammonium persulphate)? (Hint: at this point the iodine produced in reaction (1) has consumed all of the S2O3 2-) = mol of I2 d) What is the initial concentration of iodine in the reaction mixture? (Note: trick question!) [I2]i =

          1. 10.00 mL of 0.200 M potassium iodide (KI) and 20.00 mL of 0.100 M ammonium persulphate ( (NH4)2S2O8) are added to a beaker containing 10.00 mL of 0.00500 M sodium thiosulphate (Na2S2O3) solution and starch indicator. Reactions shown in equations (1) and (6) take place and a purple colour appears after 23.43 seconds.
a) Calculate the moles of thiosulphate ion (S2O3 2-) added to the reaction mixture.
= 5.00 x 10^-5 mol of S2O3 2-
b) According to equation (6), how many moles of thiosulphate are consumed for each mole of iodine (I2) formed in reaction (1) ?
answer: 2 mol
c) Therefore, how many moles of iodine were formed in the 23.43 seconds immediately following the mixing of the two reactants (potassium iodide and ammonium persulphate)? (Hint: at this point the iodine produced in reaction (1) has consumed all of the S2O3 2-)
= mol of I2
d) What is the initial concentration of iodine in the reaction mixture? (Note: trick question!)
[I2]i =

1. 10.00 mL of 0.200 M potassium iodide (KI) and 20.00 mL of 0.100 M ammonium persulphate ( (NH4)2S2O8) are added to a beaker containing 10.00 mL of 0.00500 M sodium thiosulphate (Na2S2O3) solution and starch indicator. Reactions shown in equations (1) and (6) take place and a purple colour appears after 23.43 seconds.
a) Calculate the moles of thiosulphate ion (S2O3 2-) added to the reaction mixture.
= 5.00 x 10^-5 mol of S2O3 2-
b) According to equation (6), how many moles of thiosulphate are consumed for each mole of iodine (I2) formed in reaction (1) ?
answer: 2 mol
c) Therefore, how many moles of iodine were formed in the 23.43 seconds immediately following the mixing of the two reactants (potassium iodide and ammonium persulphate)? (Hint: at this point the iodine produced in reaction (1) has consumed all of the S2O3 2-)
= mol of I2
d) What is the initial concentration of iodine in the reaction mixture? (Note: trick question!)
[I2]i =

Added by Sarah L.

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