Chemistry Lab Notebook | Lab 5: Kinetics — Determining Rate Laws
Printed Name: Signature: Date:
_______________________ ___________________________ _____________________________
___
Name: Date: Experiment #: 5 Title: Kinetics — Rate
________________ _________________ Laws
Purpose: To determine the reaction order and rate law for two reactions (H ₂O ₂ decomposition and Na ₂S ₂O ₃/HCl clock
reaction) using concentration and time data, and to evaluate the effect of temperature on reaction rate by comparing heated
and room-temperature trials of the gas evolution experiment.
Procedure Data / Results / Calculations
Part 1: Gas Evolution Reaction (H₂O₂ Part 1: Data Table
Decomposition) *Trial 4 same volumes as Trial 1, reagents heated to
1. Set up the gas-collecting apparatus: reaction ~70°C.
chamber connected to a water-filled burette and Trial H₂O₂ KI H₂O Time Rate
leveling bulb. The leveling bulb is raised or (mL) (mL) (mL) (s) (mL/s)
lowered to equalize gas and atmospheric 1 5 10 15 145 0.0966
pressure before each reading.
2 10 10 10 74 0.189
3 5 20 5 82.1 0.170
2. For each trial, combine the measured
volumes of H₂O₂, KI (catalyst), and H₂O (total 4* 5 10 15 17 0.824
volume = 30 mL) in the reaction chamber. Allow
~2 mL of gas to be produced to purge air from Order with respect to H₂O₂ (compare Trials 2 & 1):
the system. H₂O₂ doubled (5→10 mL), KI constant
Rate ratio: 0.189 ÷ 0.0966 = 1.957
3. Time how long it takes to collect the next 14 Vol ratio: 10 ÷ 5 = 2
mL of O₂ gas. Record the time in seconds.
1.957 = 2ˣ → x = log(1.957) ÷ log(2) = 0.291 ÷ 0.301 ≈
Calculate rate = 14 mL ÷ time (s).
0.966 ≈ 1
Order w.r.t. H₂O₂ = 1 (first order)
4. Run three room-temperature trials varying
Order with respect to KI (compare Trials 3 & 1):
volumes of H₂O₂ and KI (keeping total volume
constant with water). Use averaged times for KI doubled (10→20 mL), H₂O₂ constant
calculations. Rate ratio: 0.170 ÷ 0.0966 = 1.760
Vol ratio: 20 ÷ 10 = 2
5. Trial 4*: repeat Trial 1 volumes but preheat 1.760 = 2ˣ → x = log(1.760) ÷ log(2) = 0.246 ÷ 0.301 ≈
water and KI to ~70°C to test the effect of 0.817 ≈ 1
temperature on rate. Order w.r.t. KI = 1 (first order)
Rate Law: rate = k[H₂O₂]¹[KI]¹
6. To find the order with respect to each
reactant, compare two trials where only that
reactant's volume changes:
rate₂/rate₁ = (conc₂/conc₁)ˣ → solve for x using
logarithms:
x = log(rate ratio) ÷ log(conc ratio)
Part 2: Sulfur Precipitate (Clock) Reaction Part 2: Data Table
1. Prepare five test tubes with decreasing Trial S₂O₃²⁻ H₂O Molarity Final M Time Rel. Rate
volumes of 0.1 M Na₂S₂O₃ solution (10, 8, 6, 4, 2 (mL) (mL) S₂O₃²⁻ S₂O₃²⁻ (s) (1/s)
mL), making up the remaining volume to 10 mL 1 10.0 0.0 0.10 M 0.05 M 33 0.0303
with distilled water.
2 8.0 2.0 0.08 M 0.04 M 43 0.0233
3 6.0 4.0 0.06 M 0.03 M 57 0.0175
2. Add 10 mL of HCl to each test tube (total
volume = 20 mL). Start timing immediately. 4 4.0 6.0 0.04 M 0.02 M 83 0.0120
5 2.0 8.0 0.02 M 0.01 M 183 0.00546
3. Record the time (seconds) until cloudiness
(colloidal sulfur precipitate) is visible throughout Concentration Calculations (C₁V₁ = C₂V₂, C₁ = 0.1 M):
Molarity S₂O₃²⁻ (after H₂O, V=10 mL): Trial 1: (0.1)
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Printed Name: Signature: Date:
_______________________ ___________________________ _____________________________
___
Name: Date: Experiment #: 5 Title: Kinetics — Rate
________________ _________________ Laws
Purpose: To determine the reaction order and rate law for two reactions (H ₂O ₂ decomposition and Na ₂S ₂O ₃/HCl clock
reaction) using concentration and time data, and to evaluate the effect of temperature on reaction rate by comparing heated
and room-temperature trials of the gas evolution experiment.
Procedure Data / Results / Calculations
Part 1: Gas Evolution Reaction (H₂O₂ Part 1: Data Table
Decomposition) *Trial 4 same volumes as Trial 1, reagents heated to
1. Set up the gas-collecting apparatus: reaction ~70°C.
chamber connected to a water-filled burette and Trial H₂O₂ KI H₂O Time Rate
leveling bulb. The leveling bulb is raised or (mL) (mL) (mL) (s) (mL/s)
lowered to equalize gas and atmospheric 1 5 10 15 145 0.0966
pressure before each reading.
2 10 10 10 74 0.189
3 5 20 5 82.1 0.170
2. For each trial, combine the measured
volumes of H₂O₂, KI (catalyst), and H₂O (total 4* 5 10 15 17 0.824
volume = 30 mL) in the reaction chamber. Allow
~2 mL of gas to be produced to purge air from Order with respect to H₂O₂ (compare Trials 2 & 1):
the system. H₂O₂ doubled (5→10 mL), KI constant
Rate ratio: 0.189 ÷ 0.0966 = 1.957
3. Time how long it takes to collect the next 14 Vol ratio: 10 ÷ 5 = 2
mL of O₂ gas. Record the time in seconds.
1.957 = 2ˣ → x = log(1.957) ÷ log(2) = 0.291 ÷ 0.301 ≈
Calculate rate = 14 mL ÷ time (s).
0.966 ≈ 1
Order w.r.t. H₂O₂ = 1 (first order)
4. Run three room-temperature trials varying
Order with respect to KI (compare Trials 3 & 1):
volumes of H₂O₂ and KI (keeping total volume
constant with water). Use averaged times for KI doubled (10→20 mL), H₂O₂ constant
calculations. Rate ratio: 0.170 ÷ 0.0966 = 1.760
Vol ratio: 20 ÷ 10 = 2
5. Trial 4*: repeat Trial 1 volumes but preheat 1.760 = 2ˣ → x = log(1.760) ÷ log(2) = 0.246 ÷ 0.301 ≈
water and KI to ~70°C to test the effect of 0.817 ≈ 1
temperature on rate. Order w.r.t. KI = 1 (first order)
Rate Law: rate = k[H₂O₂]¹[KI]¹
6. To find the order with respect to each
reactant, compare two trials where only that
reactant's volume changes:
rate₂/rate₁ = (conc₂/conc₁)ˣ → solve for x using
logarithms:
x = log(rate ratio) ÷ log(conc ratio)
Part 2: Sulfur Precipitate (Clock) Reaction Part 2: Data Table
1. Prepare five test tubes with decreasing Trial S₂O₃²⁻ H₂O Molarity Final M Time Rel. Rate
volumes of 0.1 M Na₂S₂O₃ solution (10, 8, 6, 4, 2 (mL) (mL) S₂O₃²⁻ S₂O₃²⁻ (s) (1/s)
mL), making up the remaining volume to 10 mL 1 10.0 0.0 0.10 M 0.05 M 33 0.0303
with distilled water.
2 8.0 2.0 0.08 M 0.04 M 43 0.0233
3 6.0 4.0 0.06 M 0.03 M 57 0.0175
2. Add 10 mL of HCl to each test tube (total
volume = 20 mL). Start timing immediately. 4 4.0 6.0 0.04 M 0.02 M 83 0.0120
5 2.0 8.0 0.02 M 0.01 M 183 0.00546
3. Record the time (seconds) until cloudiness
(colloidal sulfur precipitate) is visible throughout Concentration Calculations (C₁V₁ = C₂V₂, C₁ = 0.1 M):
Molarity S₂O₃²⁻ (after H₂O, V=10 mL): Trial 1: (0.1)
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