IA on effect of inhibitor concentration lead on enzyme catalase (yeast extract) on the rate of 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 inhibitor conc Pb on enzyme catalase (yeast extract) on the rate of 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 inhibitor conc Pb on enzyme catalase (yeast extract) on the rate of decomposition of H2O2 measured using a pressure sensor.

3. Centrifuge to spin down the extract Catalase extract (clear solution used) Yeast, pressure sensor, H2O2
Diff conc Pb2+was used (0.001, 0.125, 0.25, 0.50, 1.00M).
5% (v/v) H2O2 used.
Pressure sensor to measure O2 released.
Reaction mechanism
Procedure:
5g of yeast powder added to 50ml water (10%) – centrifuge to collect catalase extract
1ml catalase extract added to 1 ml of Pb2+ solution (diff conc)
Solution added to 5ml of 5% H2O2
Rate was measured – change of pressure over time.
Hydrogen peroxide decomposition – O2 production
2H2O2→ 2H2O + O2
Effect of inhibitor conc Pb on enzyme catalase (yeast extract) on the rate of decomposition of H2O2 measured using a pressure sensor.

4. 0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 0.2 0.4 0.6 0.8 1 1.2
Rate
of
decomposition
Conc Pb/M
Rate/kPas-1
Metal chosen as they will not act as catalyst to break down H2O2
Negative control - only Pb2+ without any catalase
Positive control – only catalase without any transition metal.
Pressure increase - due to enzyme catalase, and not transition metal.
Pb conc/M Rate/kPas-1
0.001 0.5857
0.125 0.3525
0.250 0.3441
0.500 0.3261
1.000 0.3059
+ve control 1.909
-ve control 0.04919
Rate of decomposition decreases as conc Pb2+ increases.
Pb metal strong inhibitor for enzyme catalase
Diff Pb conc were used.
Rate measured as change of pressure over time.
Effect of inhibitor conc Pb on enzyme catalase (yeast extract) on the rate of decomposition of H2O2 measured using a pressure sensor.

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 inhibitor conc Pb on enzyme catalase (yeast extract) on the rate of 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
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
Effect of inhibitor conc Pb on enzyme catalase (yeast extract) on the rate of decomposition of H2O2 measured using a pressure sensor.