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(A): Pyrolusite is an ore of manganese. ...

(A): Pyrolusite is an ore of manganese.
(R) : Formula of pyrolusite is `Mn_(3)O_(4)`.

A

Both (A) and (R) are true and (R) is the correct explanation of (A)

B

Both (A) and (R) are true and (R) is not the correct explanation of (A)

C

(A) is true but (R) is false

D

Both (A) and (R) are false

Text Solution

Verified by Experts

The correct Answer is:
C
(A) is true but (R) is false
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MnO_2 is the most important oxide of manganese. MnO_2 occurs naturally as the black coloured mineral pyrolusite. It is an oxidising agent, and decomposes to Mn_3O_4 on heating to 530^(0) C. It is used in the preparation of potassium permanaga-nate and in the production of Cl_2 gas. Over half a million tonnes per year of MnO_2 is used in dry batteries When MnO_2 is fused with KOH in the presence of air, the product formed is :

MnO_2 is the most important oxide of manganese. MnO_2 occurs naturally as the black coloured mineral pyrolusite. It is an oxidising agent, and decomposes to Mn_3O_4 on heating to 530^(0) C. It is used in the preparation of potassium permanaga-nate and in the production of Cl_2 gas. Over half a million tonnes per year of MnO_2 is used in dry batteries MnO_2 dissolve in concentrated HCl to form :

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AAKASH SERIES-D-BLOCK ELEMENTS-OBJECTIVE EXERCISE-4 (ASSERTION (A) & REASON (R) TYPE QUESTIONS )
  1. (A): Zn(II) compounds are diamagnetic. (R): Zn(II) has all its elect...

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  2. (A): FeO is basic in character. (R): Oxides of transition metals are...

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  3. (A): Pyrolusite is an ore of manganese. (R) : Formula of pyrolusite ...

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  4. (A): Equivalent mass of K(2)Cr(2)O(7), when it acts as oxidizing agent...

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  5. (A): Ti(IV) in aqueous solutions is colour less. (R): Ti(IV) has no ...

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  6. (A): In alkaline medium, KMnO(4) oxidizes iodides to iodates. (R): K...

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  7. (A): Zr and Hf have nearly equal atomic radii. (R): Zr and Hf belong...

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  8. (A) Scandium is the lightest transition metal, (R) Atomic radius of ...

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  9. (A) The most common oxidation state of lanthanides is + 3. (R) Lanth...

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  10. (A): Ce^(4+) is a good oxidizing agent. (R): Sm^(2+) is a good reduc...

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  11. (A): Zinc does not show characteristic properties of transition metals...

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  12. (A): K(2)CrO(4) has yellow colour due to charge transfer (R) : CrO(4...

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  13. (A) The highest oxidation state of chromium in its compounds is + 6 ...

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  14. (A) CrO3, reacts with HCl to form chromyl chloride gas (R) Chromyl c...

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  15. (A) Tungsten has a very low melting point (R) Tungsten is a covalent...

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  16. (A) Cu^+ ion is coloured in aqueous solutions (R) Four water molecul...

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  17. (A) Equivalent mass of KMnO4 is equal to one-third of its molecular ma...

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  18. (A) Ce^(4+) is used as an oxidising agent in volumetric analysis. (R...

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  19. (A) In MnO(4)^(-) the M-O bonds are ionic . (R) The oxidation number ...

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  20. (A) Mn atom loses ns electrons first during ionization as compared to ...

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