Hydrogen Peroxide — Structure, reactions, bleaching
Hydrogen
4
JEE Qs
8%
Hard
45
min
Master the dual oxidizing and reducing nature of H2O2, understand how its reactions change with the medium, and practice volume strength calculations thoroughly.
🧮 Key Formulas
✅ Key Points for JEE
- 1Hydrogen peroxide has a non-planar, 'open-book' structure; the dihedral angle is different in gas phase (111.5°) and solid phase (90.2°).
- 2H2O2 is an amphoteric redox agent, acting as an oxidizing agent (reduced to H2O) with strong reducing agents and as a reducing agent (oxidized to O2) with strong oxidizing agents.
- 3It is thermodynamically unstable and decomposes into H2O and O2; this decomposition is catalyzed by light, rough surfaces, metal ions, and bases, necessitating storage in dark, wax-lined plastic bottles.
- 4Its bleaching action is permanent, due to the oxidation of colored substances by nascent oxygen, making it an eco-friendly bleaching agent.
- 5The 'volume strength' of H2O2 is a crucial concentration term, indicating the volume of O2 (at STP) liberated from 1 volume of the H2O2 solution upon decomposition, directly related to its molarity.
⚠️ Common Mistakes
- ✕Confusing the role of H2O2 in redox reactions; failing to recognize its ability to act as both an oxidizing and reducing agent depending on the reaction partner and medium.
- ✕Incorrectly calculating the volume strength of H2O2 or misinterpreting its meaning in quantitative problems.
- ✕Neglecting the specific storage conditions and catalysts for H2O2 decomposition, which are frequently asked in conceptual questions.
📝 Practice Questions
See allQ34.Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R. Assertion A: Loss of electron from hydrogen atom results in nucleus of ~1 . 5 × 10 – 3 pm size. Reason R: Proton H+ always exists in combined form. In the light of the above statements, choose the most appropriate answer from the options given below: (1) Both A and R are correct and R is the correct (2) A is correct but R is not correct explanation of A (3) A is not correct but R is correct (4) Both A and R are correct but R is NOT the correct explanation of A
Q41.Which of the following can reduce decomposition of H2O2 on exposure to light (1) Urea (2) Alkali (3) Glass containers (4) Dust
Q31.Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Assertion A: Hydrogen is an environment friendly fuel. Reason R: Atomic number of hydrogen is 1 and it is a very light element. In the light of the above statements, choose the correct answer from the options given below (1) A is true but R is false (2) Both A and R are true but R is NOT the correct explanation of A (3) A is false but R is true (4) Both A and R are true and R is the correct explanation of A
Q39.Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Gypsum is used for making fireproof wall boards. Reason (R): Gypsum is unstable at high temperatures. In the light of the above statements, choose the correct answer from the options given below: (1) Both (A) and (R) are correct but (R) is not the (2) (A) is correct but (R) is not correct. correct explanation of (A). (3) (A) is not correct but (R) is correct. (4) Both (A) and (R) are correct and (R) is the correct explanation of (A).
Q47.The water gas on reacting with cobalt as a catalyst forms (1) Methanal (2) Methanoic acid (3) Ethanol (4) Methanol
Q36.Given below are two reactions, involved in the commercial production of dihydrogen H2. The two reactions are carried out at temperature “T1” and “T2”, respectively T1 Cs + H2Og ⟶COg + H2g T2 COg + H2Og CatalystCO2g + H2g The temperatures T1 and T2 are correctly related as (1) T1 = T2 (2) T1 < T2 (3) T1 = 100 K, T2 = 1270 K (4) T1 > T2
NCERT Chapters
- Class 11 Chemistry Ch 9: Hydrogen