Topics to be covered

`=>` Hydrogen peroxide
`=>` Preparation of hydrogen peroxide
`=>` Physical properties
`=>` Structure of hydrogen peroxide
`=>` Chemical properties of hydrogen peroxide
`=>` Storage of hydrogen peroxide
`=>` Uses of hydrogen peroxide


Hydrogen peroxide is an important chemical used in pollution control treatment of domestic and industrial effluents.


`color{green}("๐ˆ๐ญ ๐œ๐š๐ง ๐›๐ž ๐ฉ๐ซ๐ž๐ฉ๐š๐ซ๐ž๐ ๐›๐ฒ ๐ญ๐ก๐ž ๐Ÿ๐จ๐ฅ๐ฅ๐จ๐ฐ๐ข๐ง๐  ๐ฆ๐ž๐ญ๐ก๐จ๐๐ฌ:")`

(i) Acidifying barium peroxide and removing excess water by evaporation under reduced pressure gives hydrogen peroxide.

`color{red}(BaO_2 . 8 H_2O(s) + H_2SO_4 (aq) โ†’ BaSO_4(aq) +H_2O_2 (aq) +8H_2O(l))`

(ii) Peroxodisulphate, obtained by electrolytic oxidation of acidified sulphate solutions at high current density, on hydrolysis yields hydrogen peroxide.

`color{red}(2HSO_4^(-)(aq) oversettext(Electrolysis)โ†’ HO_3SOOSO_3H (aq) oversettext(Hydrolysis)โ†’ 2HSO_4^(-) (aq) + 2H^(+)(aq) + H_2O_2(aq))`

This method is now used for the laboratory preparation of `color{red}(D_2O_2)`

`color{red}(K_2S_2O_8(s) +2D_2O(I) โ†’ 2KDSO_4(aq) +D_2O_2(l))`

(iii) Industrially it is prepared by the autooxidation of 2-alklylanthraquinols.

`color{red}(text(2 ethylanthraquinol) underset(H_2//Pd) overset(O_2(air))โ‡„ H_2O_2 + text{(Oxidised product)})`

`color{green}(โ˜…)` In this case `color{red}(1% H_2O_2)` is formed. It is extracted with water and concentrated to `color{red}(~30%)` (by mass) by distillation under reduced pressure. It can be further concentrated to `color{red}(~85%)` by careful distillation under low pressure. The remaining water can be frozen out to obtain pure `color{red}(H_2O_2)`.

Physical Properties

`color{green}(โ˜…)` In the pure state `color{red}(H_2O_2)` is an almost colourless (very pale blue) liquid.

`color{green}(โ˜…)` Its important physical properties are given in Table 9.4.

`color{green}(โ˜…)` `color{red}(H_2O_2)` is miscible with water in all proportions and forms a hydrate `color{red}(H_2O_2.H_2O)` (mp 221K).

`color{green}(โ˜…)` A `color{red}(30%)` solution of `color{red}(H_2O_2)` is marketed as `color{red}("100 volume")` hydrogen peroxide. It means that one millilitre of `color{red}(30% H_2O_2)` solution will give `color{red}("100 mL")` of oxygen at STP. Commercially marketed sample is `color{red}(10 V)`, which means that the sample contains `color{red}(3% H_2O_2).`

Q 3111491320

Calculate the strength of 10 volume solution of hydrogen peroxide.


10 volume solution of `H_2O_2` means that `1L` of this `H_2O_2` solution will give `10 L` of oxygen at STP

`underset(2xx34g = 68g)(2H_2O_2 (l)) โ†’ underset(22.7 L \ \ "at" \ \ STP)(O_2(g)+H_2O(l))`

On the basis of above equation `22.7 L` of `O_2` is produced from `68 g \ \ H_2O_2` at STP `10 L` of `O_2` at STP is produced from

`(68 xx 10)/(22.7) g = 29.9 g approx 30 g H_2O_2`

Therefore, strength of` H_2O_2` in 10 volume `H_2O_2` solution `= 30 g//L = 3% H_2O_2` solution


`color{green}(โ˜…)` Hydrogen peroxide has a non-planar structure. The molecular dimensions in the gas phase and solid phase are shown in Fig 9.3

Chemical Properties

`color{green}(โ˜…)` It acts as an oxidising as well as reducing agent in both acidic and alkaline media. Simple reactions are described below.

`color{green}("(๐ข) ๐Ž๐ฑ๐ข๐๐ข๐ฌ๐ข๐ง๐  ๐š๐œ๐ญ๐ข๐จ๐ง ๐ข๐ง ๐š๐œ๐ข๐๐ข๐œ ๐ฆ๐ž๐๐ข๐ฎ๐ฆ")`

`color{red}(2Fe^(2+) (aq) + 2H^(+)(aq) + H_2O_2 (aq) โ†’ 2Fe^(3+) (aq) + 2H_2O(l))`

`color{red}(PbS(s) + 4H_2O_2 (aq) โ†’ PbSO_4 (s) + 4H_2O (l))`

`color{green}("(๐ข๐ข) ๐‘๐ž๐๐ฎ๐œ๐ข๐ง๐  ๐š๐œ๐ญ๐ข๐จ๐ง ๐ข๐ง ๐š๐œ๐ข๐๐ข๐œ ๐ฆ๐ž๐๐ข๐ฎ๐ฆ")`

`color{red}(2MnO_4^(-) + 6 H^(+) + 5H_2O_2 โ†’ 2Mn^(2+) + 8H_2O + 5O_2)`

`color{red}(HOCl + H_2O_2 โ†’ H_3O^(+) + Cl^(-) + O_2)`

`color{green}("(๐ข๐ข๐ข) ๐Ž๐ฑ๐ข๐๐ข๐ฌ๐ข๐ง๐  ๐š๐œ๐ญ๐ข๐จ๐ง ๐ข๐ง ๐›๐š๐ฌ๐ข๐œ ๐ฆ๐ž๐๐ข๐ฎ๐ฆ")`

`color{red}(2Fe^(2+) + H_2O_2 โ†’ 2Fe^(3+) + 2 OH^(-))`

`color{red}(Mn^(2+) + H_2O_2 โ†’ Mn^(4+) + 2 OH^(-))`

`color{green}("(๐ข๐ฏ) ๐‘๐ž๐๐ฎ๐œ๐ข๐ง๐  ๐š๐œ๐ญ๐ข๐จ๐ง ๐ข๐ง ๐›๐š๐ฌ๐ข๐œ ๐ฆ๐ž๐๐ข๐ฎ๐ฆ")`

`color{red}(I_2 + H_2O_2 + 2 OH^(-) โ†’ 2I^(-) + 2H_2O+O_2)`

`color{red}(2MnO_4^(-) +3H_2O_2 โ†’ 2MnO_2 + 3O_2+2H_2O +2 OH^(-))`


`color{green}(โ˜…)` `color{red}(H_2O_2)` decomposes slowly on exposure to light.

`color{red}(2H_2O_2 (l) โ†’ 2H_2O(l) + O_2(g))`

`color{green}(โ˜…)` In the presence of metal surfaces or traces of alkali (present in glass containers), the above reaction is catalysed. It is, therefore, stored in wax-lined glass or plastic vessels in dark. Urea can be added as a stabiliser. It is kept away from dust because dust can induce explosive decomposition of the compound.


`color{green}(โ˜…)` Its wide scale use has led to tremendous increase in the industrial production of `color{red}(H_2O_2).`

`color{green}(โ˜…)` `color{green}("๐’๐จ๐ฆ๐ž ๐จ๐Ÿ ๐ญ๐ก๐ž ๐ฎ๐ฌ๐ž๐ฌ ๐š๐ซ๐ž ๐ฅ๐ข๐ฌ๐ญ๐ž๐ ๐›๐ž๐ฅ๐จ๐ฐ:")`

(i) In daily life it is used as a hair bleach and as a mild disinfectant. As an antiseptic it is sold in the market as perhydrol.

(ii) It is used to manufacture chemicals like sodium perborate and per-carbonate, which are used in high quality detergents.

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

(iv) It is employed in the industries as a bleaching agent for textiles, paper pulp, leather, oils, fats, etc.

(v) Nowadays it is also used in Environmental (Green) Chemistry. For example, in pollution control treatment of domestic and industrial effluents, oxidation of cyanides, restoration of aerobic conditions to sewage wastes, etc.