Question

What color would you expect to see when potassium manganate (VII) is combined with a) propan-1-ol and b) methylpropan-2-ol?

A) Red (for both)
B) Purple (for both)
C) Red (for a) and Green (for b)
D) Purple (for a) and Blue (for b)

Answer 1

The expected color when potassium manganate (VII) is combined with propan-1-ol is colorless, indicating reduction to Mn2+, and the color remains purple with methylpropan-2-ol as it does not easily oxidize. The correct answer is B) Purple (for both).

Step-by-step explanation:

When potassium manganate (VII) is combined with different alcohols, color changes can occur due to the oxidation of the alcohol by the strong oxidizing agent in potassium manganate (VII), also known as potassium permanganate.

In the case of propan-1-ol, the oxidation would typically lead to the formation of a carboxylic acid (propanoic acid), and in the process, the purple permanganate ion (MnO4−) is reduced to the colorless Mn2+ in acidic solution.

Therefore, for part a, the color change from purple to colorless indicates the completion of the reaction, often observed as a pinkish tint due to slight excess permanganate. However, for methylpropan-2-ol, since it is a tertiary alcohol, it resists oxidation under these conditions and no color change would be expected, indicating answer choice B) Purple (for both).