IA on effect of different transition metal (homogenous catalyst) on the decomposition of H2O2 measured using a pressure sensor.

1. Pt/Pd surface
Catalytic Properties of Transition metal
• Variable oxidation state - lose and gain electron easily.
• Use 3d and 4s electrons to form weak bond.
• Act as Homogeneous or Heterogenous catalyst – lower activation energy
• Homogeneous catalyst – catalyst and reactant in same phase/state
• Heterogeneous catalyst – catalyst and reactant in diff phase/state
• Heterogenous catalyst- Metal surface provide active site (lower Ea )
• Surface catalyst bring molecule together (close contact) -bond breaking/making easier
Transition metal as catalyst with diff oxidation states
2H2O2 + Fe2+ → 2H2O+O2+Fe3+
H2O2+Fe2+→H2O + O2 + Fe3+
Fe3+ + I - → Fe2+ + I2
Fe2+ ↔ Fe3+
Rxn slow if only I- is added H2O2 + I- → I2 + H2O + O2
Rxn speed up if Fe2+/Fe3+ added
Fe2+ change to Fe3+ and is change back to Fe2+ again
recycle
molecule adsorp on
surface catalyst
Pt/Pd surface
Bond break
Bond making
3+
CH2 = CH2 + H2 → CH3 - CH3
Nickel catalyst
Without
catalyst, Ea
CH2= CH2 + H2 CH3 - CH3
Surface of catalyst for adsorption
With catalyst, Ea
adsorption
H2
adsorption
C2H4
bond breaking
making
desorption
C2H6
Fe2+ catalyst
How catalyst work ?
Activation energy
Effect of diff transition metal on the decomposition of H2O2 measured using a pressure sensor.

2. Across period
Cr - 4s13d5
• half filled more stable
Cu - 4s13d10
• fully filled more stable
Ca
4s2
K
4s1
Transition metal have partially fill 3d orbital
• 3d and 4s electron can be lost easily
• electron fill from 4s first then 3d
• electron lost from 4s first then 3d
• 3d and 4s energy level close together (similar in energy)
Filling electron- 4s level lower, fill first Losing electron- 4s higher, lose first
3d
4s
Effect of diff transition metal on the decomposition of H2O2 measured using a pressure sensor.

3. Pressure change due to O2 gas
Effect of diff transition metal on the decomposition of H2O2 measured using a pressure sensor.
Different transition metal were used
V5+, Cr3+, Co2+, Ni2+, Mn2+, Pb2+, Cu2+, Fe2+, Fe3+
Same amount were used – 0.00005mol
5% H2O2 used.
Pressure sensor to measure O2 released.
Reaction mechanism
Procedure:
0.00005mol of each catalyst was added to H2O2
Ex: 1g of FeSO4 added to 100ml water – conc is – 0.0359M
To transfer 0.00005mol to H2O2, the vol needed will be 1.4ml
1.4ml FeSO4 was added to 1ml 5% H2O2 in a boiling tube
Pressure sensor attached. Rxn monitor by increase in pressure
1. Comparing homogenous solution (diff transition metal) against solid MnO2
2. Which transition metal works best (same amt of catalyst added, 0.0005mol)
3. Measure Ea value for diff transition metal and compared to MnO2 which is 50kJmol-1
4. Will Ea higher/lower for heterogenous catalyst (MnO2) compared to homogenous catalyst
like CuSO4, FeSO4, FeCI3
Research Questions
Hydrogen peroxide decomposition – O2 production
2H2O2→ 2H2O + O2

4. Only 4 transition metal works compared to MnO2 Slope/gradient taken over 50s
Transition
metal
Rate
kPas-1
V5+ No rxn
Cr3+ No rxn
Co2+ No rxn
Ni2+ No rxn
Mn2+ No rxn
Pb2+ No rxn
Cu2+ 0.009316
Fe2+ 0.03559
Fe3+ 0.1086
MnO2 0.4422
Diff homogenous solution compared to solid MnO2 catalyst.
Rate measured as pressure change over time.
Effect of diff transition metal on the decomposition of H2O2 measured using a pressure sensor.
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
Cu2+ Fe2+ Fe3+ MnO2
Rate
of
reaction
Rate of reaction vs diff transition metal
Homogenous catalyst vs MnO2. Fe3+ works best as and
will be chosen for Ea study

5. Method 1 Method 2
Time Time
Volume Pressure
• Rate = Δ vol O2 over time
• Volume recorded
• Rate = Δ pressure O2 over time
• Pressure recorded
Procedure
2H2O2 → O2 + 2H2O
Rxn: H2O2 with diff (catalyst) measured using TWO diff methods
• 2H2O2 → O2 + 2H2O
(H2O2 limiting, KI excess)
• Pipette 1ml 1.0M KI to 20ml of 1.5% H2O2
• Vol O2 released recorded at 1 min interval
• Repeated using 3% H2O2 conc
Time/m Vol O2
(H2O2 1.5%)
Vol O2
(H2O2 3.0%)
0 0.0 0.0
1 8.5 14.0
2 15.0 26.5
3 21.0 34.0
4 26.0 39.0
Volume O2
Time
3 %
1.5 %
Effect of diff transition metal on the decomposition of H2O2 measured using a pressure sensor.

6. • 2H2O2 → O2 + 2H2O
(H2O2 limiting, KI excess)
• Pipette 1ml 1.0M KI to 20ml of 1.5% H2O2
• Pressure O2 released recorded at 1 min interval
• Repeat using 3% H2O2 conc
Techniques Used to measure Rate of Rxn
Method 1 Method 2
Time Time
Volume Pressure
• Rate = Δ vol O2 over time
• Volume recorded
• Rate = Δ pressure O2 over time
• Pressure recorded
Procedure
2H2O2 → O2 + 2H2O
Time
3 %
1.5 %
Time/m Pressure O2
(H2O2 1.5%)
Pressure O2
(H2O2 3%)
0 101.3 101.3
1 102.4 103.4
2 103.5 105.6
3 110.3 115.2
4 113.5 118.2
Pressure O2
Rxn: H2O2 with diff (catalyst) measured using TWO diff methods