The reaction H_2S+H_2O_2\rightarrow S+2H_2O describes:

The reaction H_2S+H_2O_2\rightarrow S+2H_2O manifests oxidizing nature of H_2O_2 as it oxidises S from -2 to 0 oxidation states.Hence option C is correct.

(a) H_2O_2 + O_3 \rightarrow H_2O + 2O_2 (b) H_2O_2 + Ag_2O \rightarrow 2Ag + H_2O + O_2 Role of hydrogen peroxide in the above reactions is respectively:

(a) H_2O_2 + O_3 \rightarrow H_2O + 2O_2 In this reaction, O_3 is reduced into O^{-2} ion .(b) H_2O_2 + Ag_2O \rightarrow 2Ag + H_2O + O_2 In this reaction, Ag_2O is reduced to Ag .Hence, H_2O_2 acts as reducing agent in both the reactions.

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>>Class 11
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>> $Hydrogen Peroxide$

Hydrogen Peroxide

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Hydrogen Peroxide - preparation, Properties, Structure and Uses

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Q: Half litre each of three samples of H_{2}O_{2} labelled 10 volume, 15 volume and 20 volume are mixed and then diluted with equal volume of water. The relative strength of resultant H_{2}O_{2} solution is:

Volume strength of H_{ 2 }{ O }_{ 2 } = 5.6\times \text{N} (\text{N} = Normality ) Normality of 10 vol of H_{ 2 }{ O }_{ 2 } = \dfrac{10}{5.6}\text{N} Normality of 15 vol of H_{ 2 }{ O }_{ 2 } = \dfrac{15}{5.6} \text{N} Normality of 20 vol of H_{ 2 }{ O }_{ 2 } = \dfrac{20}{5.6} \text{N} Let 500 ml of each is mixed, then the total volume of mix = 1500 ml.Also, this is diluted to double its volume, i.e., = 3000 ml \text{N}\times 3000 = \dfrac { 10 }{ 5.6 } \times 500+\dfrac { 15 }{ 5.6 } \times 500+\dfrac { 20 }{ 5.6 } \times 500 Normality of H_{ 2 }{ O }_{ 2 } mix = 1.339\:\text{N} Vol. strength of H_{ 2 }{ O }_{ 2 } = 1.339 \times 5.6 = 7.5 .

Q: From the following statements regarding H_2O_2 , choose the incorrect statement?

(A) Hydrogen peroxide can act as oxidizing as well as reducing agent.For example, in acidic medium, it oxidizes ferrous ions to ferric ions. 2Fe^{2+} +H_2O_2 +2H^+\rightarrow 2Fe^{3+} +2H_2O In acidic medium, hydrogen peroxide reduces HOCl to chloride ion. HOCl + H_2O_2 \rightarrow H^++Cl^-+H_2O + O_2 Thus, the option A is incorrect.(B) It decomposes on exposure to light to form water and oxygen. 2H_2O_2 \rightleftharpoons 2H_2O + O_2 Thus, the option (B) is correct.(C) It has to be stored in plastic or wax, lined glass bottles in dark to prevent its decomposition.Thus, the option (C) is correct.(D) It has to be kept away from dust as it decomposes in presence of dust.Thus, the option (D) is correct.

Q: In which of the following reactions, H_{2}O_{2} acts as a reducing reagent ?

HOCl + H_{2}O_{2}\overset{H^+}{\rightarrow}H_{3}O^{+} + Cl^{-} + O_2 Here, the H_2O_2 act as the reducing agent, as the Cl has +1 oxidation state of in HOCl and after reaction with the H_2O_2 , in the presence of the acid, it reduces the Cl in HOCl to Cl^{-} having -1 oxidation state. So, as Cl oxidation state decreases from the +1 to -1 oxidation state, hence the H_2O_2 is acting as the reducing agent.

Q: Hydrogen peroxide is prepared in the laboratory by:

Hydrogen peroxide can be prepared in the laboratory by the action of ice cold, dilute sulphuric acid on sodium peroxide or hydrated barium peroxide (BaO_2. 8H_2O) . A calculated quantity of sodium peroxide is added in small quantities to 20\% ice cold solution of sulphuric acid. The reaction is as follows: Na_2O_2(s) + H_2SO_4\rightarrow Na_2SO_4(s) + H_2O_2(l) Most of the sodium sulphate separates out on cooling as crystals of Na_2SO_4.10H_2O . Thus, 30\% of hydrogen peroxide containing small amount of sodium sulphate is obtained. Barium peroxide is made into a thin paste and added slowly to ice-cold dilute sulphuric acid. The reaction is as follows: BaO_2(s) + H_2SO_4(aq)\rightarrow BaSO_4(s) + H_2O_2(l) Barium sulphate is allowed to settle down as a precipitate and filtered off. The filtrate obtained is a dilute solution of hydrogen peroxide. Phosphoric acid can be used in place of sulphuric acid. Alternatively, carbon dioxide gas may be passed through hydrated barium peroxide paste in ice cold water, in a slow stream. 2BaO_2(s) + 2H_3PO_4(aq)\rightarrow Ba(PO_4)_2(s) + 3H_2O_2(l) BaO_2(s) + CO_2 + H_2O_2\rightarrow BaCO_3(s) + H_2O_2(l) The precipitated barium peroxide or barium carbonate is filtered off which leaves hydrogen peroxide.

Q: The reaction of aqueous KMnO_4 with H_2O_2 in acidic conditions gives:

The reaction of aqueous KMnO_4 with H_2O_2 in acidic conditions gives: 3H_2SO_4+ 2KMnO_4 + 5H_2 O_2 \rightarrow 5O_2 + 2MnSO_4 + 8H_2O + K_2SO_4 The oxidation number of Mn in MnSO_4 is +2 .Hence, option B is correct.

Q: H_{2}O_{2} acts as an oxidising agent in:

Because the oxidation state of oxygen in { H }_{ 2 }{ O }_{ 2 } is -1 which can be oxidized to 'O' oxidation state by removing an { e }^{ - } or else can be reduced by adding an { e }^{ - } and oxidation state would be reduced to -2 oxidizing agent means oxidizing others itself getting reduced.Acidic: { H }_{ 2 }{ O }_{ 2 }+2{ H }^{ + }+2{ e }^{ - }\rightarrow 2{ H }_{ 2 }O .Basic: { H }_{ 2 }{ O }_{ 2 }+2{ e }^{ - }\rightarrow 2{ OH }^{ - }

Q: Compare the structures of H_2O and H_2O_2 .

The central O atom in water is \displaystyle sp^3 hybridized and two O-H bonds are present. Two lone pairs of electrons are present in two \displaystyle sp^3 hybrid orbitals. Water molecule has bent geometry with H-O-H bond angle of \displaystyle 104.5^o . The structure of \displaystyle H_2O_2 is non planar. A single covalent bond is present between 2 O atoms. Each O atom is covalently bonded to one H atom. Two O-H bonds are in different planes and the dihedral angle between the planes is \displaystyle 111.5^o in the gas phase.

Q: The bleaching action of H_{2}O_{2} is due to which one of the following reactions?

The bleaching action of H_2O_2 is due to the following reaction: H_{2}O_{2}\rightarrow H_{2}O+[O] The nascent oxygen formed reacts with organic material and breaks bonds in them. This bleaches the compound. Thus, hydrogen peroxide has a bleaching action due to its oxidising nature.