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Pick out the correct statement(s)
  • a)
    MnO2 dissolves in conc. HCl, but does not form Mn4+ ions.
  • b)
    Decomposition of acidic KMnO4 is catalysed by sunlight.
  • c)
    MnO2−4 is oxidising and stable only in very strong alkali. In dilute alkali, water or acidic solutions it disproportionates.
  • d)
    KMnO4 does not act as an oxidising agent in alkaline medium.
Correct answer is option 'A,B,C'. Can you explain this answer?
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Pick out the correct statement(s)a)MnO2 dissolves in conc. HCl, but d...
Explanation:

a) MnO2 dissolves in conc. HCl, but does not form Mn4+ ions:
When MnO2 is dissolved in concentrated HCl (hydrochloric acid), it undergoes the following reaction:
MnO2 + 4HCl → MnCl2 + Cl2 + 2H2O
In this reaction, MnO2 is reduced to Mn2+ ions, and chlorine gas (Cl2) is evolved. Therefore, MnO2 does not form Mn4+ ions in this reaction.

b) Decomposition of acidic KMnO4 is catalyzed by sunlight:
When acidic KMnO4 (potassium permanganate) is exposed to sunlight, it undergoes photochemical decomposition. Sunlight provides the energy required for the decomposition reaction to occur. The reaction can be represented as follows:
2KMnO4 + H2SO4 → K2SO4 + 2MnO2 + 2H2O + [3O2]
In this reaction, KMnO4 is reduced to MnO2, and oxygen gas (O2) is evolved. The presence of sunlight speeds up this decomposition reaction.

c) MnO2−4 is oxidizing and stable only in very strong alkali. In dilute alkali, water or acidic solutions, it disproportionates:
MnO2−4 refers to the manganate ion (MnO4) with a charge of -2. In very strong alkali solutions, MnO2−4 is stable and acts as an oxidizing agent. However, in dilute alkali, water, or acidic solutions, it undergoes disproportionation. Disproportionation refers to a redox reaction where a species is simultaneously oxidized and reduced. The reaction can be represented as follows:
3MnO4− + 4H2O → 2MnO4−2 + MnO2 + 8OH−
In this reaction, some of the manganate ions are reduced to manganate (MnO4−2) ions, while others are oxidized to MnO2. The reaction occurs in dilute alkali, water, or acidic solutions due to the presence of suitable reducing agents or oxidizing agents.

d) KMnO4 does not act as an oxidizing agent in alkaline medium:
In an alkaline medium, KMnO4 (potassium permanganate) does not act as a strong oxidizing agent. It undergoes reduction to form MnO2, but the reaction is not as vigorous as in acidic medium. In alkaline medium, other oxidizing agents such as hydrogen peroxide (H2O2) are more effective. Therefore, KMnO4 is not commonly used as an oxidizing agent in alkaline solutions.

Conclusion:
The correct statements are:
a) MnO2 dissolves in conc. HCl, but does not form Mn4+ ions.
b) Decomposition of acidic KMnO4 is catalyzed by sunlight.
c) MnO2−4 is oxidizing and stable only in very strong alkali. In dilute alkali, water, or acidic solutions, it disproportionates.
Statement d) is incorrect as KMnO4 does not act as an oxidizing agent in
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Community Answer
Pick out the correct statement(s)a)MnO2 dissolves in conc. HCl, but d...
2. Decomposition of acidified KMnO4 is catalysed by sunlight.
3.
4. KMnO4 also acts as an oxidizing agent in alkaline medium:
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There are many reactions which obey a first order rate equation although it reality they are bi- or ter-molecular. As an example of these may be taken the decomposition of Carbonyl sulfide in water, namely, COS + H20 002 + H2SAccording to the law of mass action this reaction should be second order with the rate dependent on the concentration of both the carbonyl sulfide and the water. Actually however, the rate is found to be first order with respect to the carbonyl sulfide and independent of the water Reactions exhibiting such behaviour are said to be pseudo-molecular.The pseudo-unimoecuar nature of this reaction is explainable by the fact that water is present in such excess that its concentration remains practically constant during the course of the reaction. Under these condition b x = b, and the rate equation becomesOn integration this leads towhich is the equation for a first order reaction. It is evident, however, that the now constant k is not independent of the concentration, as is the case with true first order constants, but may vary with b if the latter is changed appreciably, When such is the case, the true constant k2 can be obtained from k by dividing the latter by b. pseudo-molecular reactions are encountered whenever one or more of the reactants remain constants during the course of an experiment. This is the case with reactions conducted in solvents which are themselves one of the reactants, as in the decomposition of carbonyl sulfide in water, or in the esterification of acetic anhydride in alcohol(CH3C0)20 + 2C2H5OH 2CH3C00C2H5 + H20Again, this is also true of reactions subject to catalysis, in which case the concentration of the catalyst does not change. The decomposition of diacetone alcohol to acetone in aqueous solution is catalysed by hydroxyl ions, with the rate proportional to the concentration of the alcohol and that of the base. Since the concentration of the base does not change within any one experiment, however, the rate equation reduces to one of first order with respect to the alcohol. But the rateconstant k obtained for various concentrations of base are not identical, as may be seen from table. To obtain from these the true second order velocity constant, the ks must be divided by the hydroxyl ion concentration. When this is done excellent k2 values result, as column 3 indicatesTable : Decomposition of diacetone alcohol in water at 25C (Catalyst : NaOH)Q.By what factor does the rate of reaction of diacetone alcohol in water solution change if p0H is increased by 2 units other things remaining same ?

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Pick out the correct statement(s)a)MnO2 dissolves in conc. HCl, but does not form Mn4+ ions.b)Decomposition of acidic KMnO4 is catalysed by sunlight.c)MnO2−4 is oxidising and stable only in very strong alkali. In dilute alkali, water or acidic solutions it disproportionates.d)KMnO4 does not act as an oxidising agent in alkaline medium.Correct answer is option 'A,B,C'. Can you explain this answer?
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Pick out the correct statement(s)a)MnO2 dissolves in conc. HCl, but does not form Mn4+ ions.b)Decomposition of acidic KMnO4 is catalysed by sunlight.c)MnO2−4 is oxidising and stable only in very strong alkali. In dilute alkali, water or acidic solutions it disproportionates.d)KMnO4 does not act as an oxidising agent in alkaline medium.Correct answer is option 'A,B,C'. Can you explain this answer? for JEE 2024 is part of JEE preparation. The Question and answers have been prepared according to the JEE exam syllabus. Information about Pick out the correct statement(s)a)MnO2 dissolves in conc. HCl, but does not form Mn4+ ions.b)Decomposition of acidic KMnO4 is catalysed by sunlight.c)MnO2−4 is oxidising and stable only in very strong alkali. In dilute alkali, water or acidic solutions it disproportionates.d)KMnO4 does not act as an oxidising agent in alkaline medium.Correct answer is option 'A,B,C'. Can you explain this answer? covers all topics & solutions for JEE 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Pick out the correct statement(s)a)MnO2 dissolves in conc. HCl, but does not form Mn4+ ions.b)Decomposition of acidic KMnO4 is catalysed by sunlight.c)MnO2−4 is oxidising and stable only in very strong alkali. In dilute alkali, water or acidic solutions it disproportionates.d)KMnO4 does not act as an oxidising agent in alkaline medium.Correct answer is option 'A,B,C'. Can you explain this answer?.
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