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Chemistry > KMnO4 > Flashcards

KMnO4 Flashcards

1
Q
A
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2
Q
A
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3
Q

What is the chemical formula of potassium permanganate?

A

KMnO₄

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4
Q

How is potassium permanganate (KMnO₄) prepared?

A

By fusion of MnO₂ with an alkali metal hydroxide (like KOH) and an oxidizing agent (like KNO₃), producing K₂MnO₄, which disproportionates in a neutral or acidic solution to form KMnO₄.

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5
Q

What is the color of K₂MnO₄?

A

Dark green.

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6
Q

Write the reaction for the formation of manganate from manganese dioxide.

A

2MnO₂ + 4KOH + O₂ → 2K₂MnO₄ + 2H₂O

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7
Q

What happens to manganate ions (MnO₄²⁻) in a neutral or acidic solution?

A

They disproportionate to form permanganate ions (MnO₄⁻) and manganese dioxide (MnO₂).

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8
Q

Write the reaction for the disproportionation of manganate ions (MnO₄²⁻) in an acidic solution.

A

3MnO₄²⁻ + 4H⁺ → 2MnO₄⁻ + MnO₂ + 2H₂O

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9
Q

What is the commercial method of preparing potassium permanganate?

A

Alkaline oxidative fusion of MnO₂ followed by electrolytic oxidation of manganate (VI).

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10
Q

What is the oxidation state of manganese in manganate ion (MnO₄²⁻)?

A

6

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11
Q

What is the oxidation state of manganese in permanganate ion (MnO₄⁻)?

A

7

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12
Q

What is the oxidation state of manganese in MnO₂?

A

4

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13
Q

What is the role of KNO₃ in the preparation of KMnO₄?

A

KNO₃ acts as an oxidizing agent during the fusion process.

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14
Q

What is the color of permanganate ion (MnO₄⁻)?

A

Purple.

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15
Q

Why does K₂MnO₄ undergo disproportionation in acidic or neutral solution?

A

Because Mn in the +6 oxidation state is unstable and disproportionates into Mn⁷⁺ (MnO₄⁻) and Mn⁴⁺ (MnO₂).

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16
Q

Write the reaction showing the electrolytic oxidation of manganate ions.

A

MnO₄²⁻ → MnO₄⁻ (Electrolysis)

17
Q

What is the role of air or KNO₃ in the preparation of manganate?

A

They serve as oxidizing agents to convert MnO₂ to MnO₄²⁻ (manganate ion).

18
Q

Why is KMnO₄ a strong oxidizing agent?

A

Because Mn in KMnO₄ is in the +7 oxidation state, which is highly oxidizing.

19
Q

What is the role of alkaline medium in the preparation of manganate?

A

The alkaline medium stabilizes the manganate ion (MnO₄²⁻) during its formation.

Chemistry (10 decks)

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