Hydrogen Peroxide

Hydrogen peroxide

2 2 2 4 2 4 2 2

20% ice cooled 30% solutionsolution

1. Na O H SO Na SO H O

2. From Barium peroxide

2 2 2 4 4 2 2 2BaO .8H O H SO BaSO 8H O H O

Barium sulphate is filtered off leaving behind H2O2.

Methods of preparation

3. By electrolysis of 50% H2SO4

electrolysisH2SO4

4H HSO

At cathode 22H 2e H

At Anode 4 2 2 8Peroxydisulphuric acid

2HSO H S O 2e

distilled2 2 8 2 2 2 2 4

at reduced pressureH S O 2H O H O 2H SO

H2O2 distills first leaving behind the H2SO4 which is recycled.

4. By auto oxidation of 2-ethylanthraquinol

The H2O2 obtained by this method is further concentrated by distillation under reduced pressure.

OH

OH

C2H5

2-ethyl anthraquinol

O

O

C2H5

2-ethyl anthraquinone

air (O2)

Physical Properties In the pure state H2O2 is an almost colourless(very pale blue) liquid.

H2O2 is miscible with water in all proportions and forms a hydrate H2O2.H2O

A 30% solution of H2O2 is marketed as ‘100 volume’ hydrogen peroxide.

Structure of hydrogen peroxide

H

95.0 pm

147.5 pm90.2°

101.9°

H

H

95.8 pm

147.8 pm90.2°

101.9°

H

Gas phase Solid phase

Structure of hydrogen peroxide

Oxidising properties

4 2 4 2 2 2 4 3 2(i) 2FeSO H SO H O Fe (SO ) 2H O

2 3 2 2 2 4 2(ii) H SO H O H SO H O

2 2 4 2Black White

(iii) PbS 4H O PbSO 4H O

Chemical Properties

Oxidising properties

4 6 2 4 2 2(iv) 2K Fe(CN) H SO H O

6 6 2 2 6 5 2Phenol

(v) C H H O C H OH H

2 2 2 3 2(vii) NaNO H O NaNO H O

2 2 7 2 4 2 2 2 4 5 2(viii) K Cr O H SO 4H O K SO CrO 5H O

3 6 2 2 42K Fe(CN) 2H O K SO

Reducing properties

2 2 3 2 2(i) H O O H O O

2 2 2 2 2 2(ii) Ag O H O 2Ag H O O

2 3 2 2 3 2 2 2(iii) PbO 2HNO H O Pb(NO ) 2H O O

Reducing properties4 2 4 2 2(iv) 2KMnO 3H SO 5H O

2 2 2 2(v) Cl H O 2HCl O

4 2 2 2(vi) 6KAuCl 3H O 2Au 2KCl 6HCl 3O

2 4 4 2 2K SO 2MnSO 8H O 5O

Acidic properties

It reacts with alkalies and decomposes carbonates.

2 2 2 2 2H O 2NaOH Na O 2H O

2 2 2 3 2 2 2 2H O Na CO Na O H O CO

For bleaching silk, wool, hair and leather

As rocket fuel

Dilute solution is sold in name ‘perhydrol’

It is used in the synthesis of hydroquinone, tartaric acid and certain food products and pharmaceuticals (cephalosporin) etc.

Uses of hydrogen peroxide

H2O2 is stored in the bottles lined with wax because the rough glass surface causes the decomposition of hydrogen peroxide.

Storage

H2O2 decomposes slowly on exposure to light.

Volume strength of hydrogen peroxide Calculate the percentage strength of a 10 volume H2O2 solution.

10 volume hydrogen peroxide means that 1 ml of such a solution of hydrogen peroxide on heating will produce 10 ml of oxygen at N.T.P.

2 2 2 22H O 2H O O

2(2 + 32) gm 22.4L at N.T.P.

= 68 gm or 22400 cm3 at N.T.P.

2 2 222400 ml of O is liberated from = 68 gm of H O

Solution2

2 2

10 ml of O is liberated from=

6810 gm of H O

22400

But 10 ml of O2 at N.T.P. are produced from 1 ml of 10 volume H2O2 solution.

2 2

2 2

1 ml of 10 volume H O solution contains =

6810 gm of H O

22400

= 0.03035 gm

2 2100 ml of 10 volume H O solution contains

= 0.03035 × 100

= 3.035 gm

= 3.035%

Illustrative exampleCalculate the normality of 30 volume of H2O solution:

Solution:

2 2 22H O 2H O O

2(2 + 32) gm 22.4 L= 68 gm

22.4 L of O2 is produced from = 68 gm of H2O2

6830 gm

22.4

= 91.07 gm/mLStrength of 20 volume H2O2 solution

2 30 L of O is produced from

Solution

2 2 2 22H O 2H O O

68 parts by weight 32 parts by weight

32 parts by weight of oxygen is obtained from = 68 parts by weight of H2O2

parts by weight of oxygen is obtained from = 68

8 1732

Strength 91.07Normality 5.35

Equivalent weight 17

2 2Equivalent weight of H O = 17