1

Catalyst and Catalytic Effect

Collect

◼ Plastic basin

◼ Watch glass

◼ 50 mL graduated cylinders (2)

◼ Plastic droppers (2)

◼ Cotton gloves

◼ Timer (by TA)

Prepare

◼ Test tubes (wash and dip dry)

◼ Test tube rack

◼ Tweezers

◼ 50 mL graduated cylinder

◼ 100 mL beaker

Share

◼ Knife and scissors

◼ Evaporating dish

◼ carton box

◼ Spray

◼ Incense and match (in hood)

2021/03/02 revised

2

Objective

◼ Decomposition of hydrogen peroxide

◼ Chemiluminescence of luminol

◼ Catalytic effect of catalyst

Techniques

◼ Weighing

◼ Magnetic stirrer and hot plate

◼ Graduated cylinder and dispenser

◼ Liquid nitrogen

Objective & Techniques

3

I. Decomposition of Hydrogen Peroxide

2 H2O2(aq) Catalyst O2(g) + 2 H2O(l)

發光胺

NH2 O

O

NH

NH+ 2OH- + 2H2O2

Iron ions+ 4H2O + N2

基態

hν

O-

O-

O

ONH2

4

II. Chemiluminescence of Luminol

*

Luminol

Ground state

Catalytic Effect of Catalyst

▪ Catalyst

A catalyst is a substance

which increases the rate of

a chemical reaction

▪ Types

– Homogeneous catalyst

– Heterogeneous catalyst

– Biocatalyst (enzyme)

▪ Mechanism?

5

6

Enzyme

◼ Enzyme: a biocatalyst

◼ Characteristics

– High specificity

– High efficiency

– Activity affected by pH, temperature… etc.

▪ Why?

▪ Protein: a polymer of amino acids

▪ Possess specific function for special structure

7

Experimental Flowchart

I. Decomposition of H2O2

by catalyst

– MnO2(s)

– KI(aq)

– Pig liver

• Fresh

• Frozen

• Boiled

– Blood from pig liver

II. H2O2 and luminol

– Pig liver blood

– K3[Fe(CN)6]

– K4[Fe(CN)6]

III. Forensic chemistry

– Detection of blood

Step I. MnO2 and H2O2

• Weigh 0.1 g MnO2

and add 3 d

dishwashing liquid

into 50 mL graduated

cylinder

8

• Add 5 mL H2O2 soln

• Mix well

• Record rxn time and

volume of bubbles

formed

• Insert burning

incense into gas

bubbles

• Inspect the property

of gas evolved

Step II. KI Solution and H2O2

Add 1 mL 2.0 M KI(aq)

and 3 d dishwashing liquid

To 50 mL graduated cylinder

Add 5 mL 10 mL 2%H2O2

Mix well

Record rxn time and volume

Test with burning incense 9

▪ Take 3 pieces of 50 mL graduated

cylinder

▪ Add 3 d dishwashing liquid and

1) Fresh pig liver

2) Frozen pig liver

3) Boiled pig liver

4) Blood from pig liver

10

Record:

Rxn time &

bubble volumes

Cut to slices Freeze pig liver in liquid

nitrogen

5 mL of 3%H2O2

Step III. Pig Liver and H2O2

Step IV. Luminol and H2O2

Take 5 test tubes, each filled with

(1) 1 mL H2O & 2 d. blood from pig liver

(2) 1 mL 0.2 M K3Fe(CN) 6

(3) 1 mL 0.2 M K4Fe(CN)6

(4) 1 mL H2O & 1 d. K3Fe(CN) 6

(5) 1 mL H2O & 5 d. K3Fe(CN) 6

Use a test tube to take 3 mL luminol test

soln

Add 0.5 mL of luminol test soln to #(1)~(5)

one by one

Observe and record chemiluminescence

Add more Fe(III) to tubes (4) and (5)11

Step V. Luminol and Forensic

Collect the luminol test

soln left in a spray

12

Spray the luminol test soln

on to tissue, knife, or

scissors used

Take the picture for

recording

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Summary I

3 d

dishwashing

liquid

+

5 mL

3%H2O2

Catalyst

0.1 g MnO2(s)

1 mL KI(aq)

Fresh pig liver

Frozen pig liver

Boiled pig liver

2 d Blood from pig liver

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Summary II

Test tube Reagent

1 mL H2O2 + 2 d. pig liver blood

0.5 mL

Luminol

test soln

1 mL 0.2 M K3Fe(CN) 6 +

1 mL 0.2 M K4Fe(CN)6

1 mL H2O & 1 d. K3Fe(CN) 6

1 mL H2O & 5 d. K3Fe(CN) 6

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Notice

◼ Start counting time while H2O2(aq) being added to

the reacting solution

◼ Take and place burning incense back into fume

hood to avoid smoke accumulating in lab.

◼ Wear cotton gloves to avoid burned by hot plate or

boiling water

◼ Be cautious of operating with liquid nitrogen for low

temperture

◼ Recycle the plastic droppers after used

◼ Boil all the pig liver after use and recycle

◼ Give the timer back to TA

◼ Clean the apparatus, lab bench after class

Brief report

16

Dispenser

1. Check the pre-set volume and

do not change the volume

setting afterwards.

2. Position the flask under the tip

of dispenser.

3. Lightly pull the piston pump up

and down several times to get

rid of the bubbles.

4. Lightly pull piston pump up to

the top, then slowly push down

to obtain the measured solution.

（2）

（1）

（3）

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