Class 11 unit 8: Redox reactions is one of the most important chapters of physical chemistry for academic and competitive preparations like IIT-JEE, NEET, AIIMS, State PSCs, UPSC etc., and the Chemistry Olympiads. It is one of those chapters therefrom numerals are frequently asked in academic and competitive examinations. It is a hot spot of chemistry and needs special attention to score high in all the chemistry competitions. objective questions on Redox reactions contain the most important and the most expected multiple-choice questions (MCQs) along with their solution and explanation. These questions would be very helpful for chemistry competitions.
Important MCQs on Redox Reactions with Explanation
Q.1.Which of the following is the example of auto-oxidation-
(a) Formation of H2O by the decomposition of H2O2.
(b) Formation of H2O2 by the oxidation of H2O.
(c) Both (a) and (b)
(d) None of the above
Ans.-(b) Formation of H2O2 by the oxidation of H2O
Explanation-Self-oxidation of any substance in presence of oxygen is called auto-oxidation of the substance. This term is usually used to describe the degradation of organic compounds in air (as a source of oxygen) to produce hydroperoxides and cyclic organic peroxides which react further to form other products. This process is responsible for aging, spoilage of foods, degradation of petrochemicals etc. Auto-oxidation may occur in a situation where it is not desired. For example, destructive cracking of the rubber of automobile tires and rancidification.
Water also gets oxidized to hydrogen peroxide in presence of air and it is an example of auto-oxidation. Here, the oxidation number of oxygen increases from -2 to -1.
Formation of H2O by the decomposition of H2O2 involves the decrease of the oxidation number of oxygen from -1 to -2. Hence, it is not the example of oxidation, but it is the example of reduction.
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