Lab #1 Reaction Kinetics in Redox Reactions

Procedure:

Step 1: Prepare solution of sodium thiosulfate, place 0.25gm (250 mg) of Na2S2O3 in 100ml beaker, add 20 ml of water and mix until dissolved.

Step 2: Prepare solution of potassium iodine. Add 10 gm of KI to a 100 ml beaker and add 20 ml of water and mix until dissolved.

Step 3: Obtain a 600 ml beaker, add KI and Na2S2O3 solutions, then add 60ml of 1M HCl.

Step 4: Finally add 50ml of .1M H2O2, as soon as the H2O2 is added start timing the reaction. Stop timing when the Iodine appears (solution changes color). Record time.

Step 5: Varying [H2O2] while holding [I-] constant. (2 more runs)
Repeat step 1
Repeat step 2 except with 20 gm and then 40 gm of KI
Repeat step 3
Add extra 150 ml and then 450 ml of water to the 600 ml beaker
Repeat step 4, record times for 300 ml and 600 ml solutions

Step 6: Varying [I-] while holding [H2O2] constant. (3 runs)
Repeat step1
Repeat step 2
Repeat step 3
First run add no extra water, second run add 100 ml , third run add 300 ml of water
Repeat step 4, first run add 50 ml, second run 100 ml and third run add 200 ml of .1M H2O2
Record times for 150ml, 300 ml and 600 ml solutions

Observation:

Times (secs):

run 1: 48 run 2: 48 run 3: 47 run 4: 48 run 5: 45 run 6: 44

rate = d[H2O2]/dt = (moles of H2O2 consumed) / (Total volume * Reaction Time)

moles of H2O2 consumed = .5 * moles S2O3 2- moles S2O3 2- = .25 gm / GMW (Na2S2O3) = .25/ 158.1 = .00158 moles of H2O2 consumed = .5 *.00158 = .00079

rates:

run 1: .00000011 run 2: 5.486111e-8 run 3: 2.801418e-8 run 4: .00000011 run 5: 5.851852e-8 run 6: