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in a virtual lab: redox of Mn 0.01 M KMnO4 is added to 3 different solutions: 1)...

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sandblom | eNotes Newbie

Posted August 21, 2013 at 5:39 PM via web

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in a virtual lab: redox of Mn

0.01 M KMnO4 is added to 3 different solutions:

1) acidified solution: H2SO3 + NaHSO3 + KMnO4 = ?

2) control solution: NaHSO3 + KMnO4 = ?

3) basified solution: NaOH + NaHSO3 + KMnO4 = ?

I need help figuring out what the products of these 3 reactions will be...

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llltkl | College Teacher | (Level 3) Valedictorian

Posted August 21, 2013 at 6:33 PM (Answer #1)

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The oxidation state of manganese in potassium permanganate is +7, which is reduced by `NaHSO_3` to different degrees to form various oxidation states, and corresponding colour changes are observed.

In neutral solution (control), orange colour is observed due to the formation of `MnO_2` .

In the basified solution, green colour due to `Mn^(+7)` is observed.

In the acidic solution, a faint pink colur is obtainable due to the formation of `Mn^(2+)` ions.

The balanced chemical reactions are as follows:

Neutral:

`3NaHSO_3 + 2KMnO_4 +NaOH rarr K_2SO_4 + 2Na_2SO_4 + 2MnO_2(s) + 2H_2O`

Basic:

`NaHSO_3 + 3 NaOH + 2 KMnO_4 rarr Na_2SO-4 + Na_2MnO_4 + K_2MnO_4 + 2H_2O`

Acidic:
`4NaHSO_3 + H_2SO_3 + 2KMnO_4 rarr K_2SO_4 + 2Na_2SO_4 + 2MnSO_4 +3H_2O`

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