Answer:
Step-by-step explanation:
When a spatula of potassium manganate(VII), KMnO4, is added to water, several chemical reactions occur.
Initially, potassium manganate(VII) dissolves in water, forming a purple-colored solution due to the oxidation of water molecules by the highly reactive manganese(VII) ion:
2KMnO4 + 3H2O → 2MnO2 + K2O + 6OH-
The hydroxide ions (OH-) produced in this reaction can cause the pH of the solution to become basic.
Next, the dissolved potassium manganate(VII) can act as an oxidizing agent and oxidize any reducing agents present in the solution. For example, if the solution contains any reducing sugars, such as glucose, they will be oxidized to form carboxylic acids:
C6H12O6 + 6KMnO4 + 8H+ → 6CO2 + 6H2O + 6K+ + 2MnO2
The MnO2 produced in these reactions can cause the color of the solution to change from purple to brown. The extent of the color change depends on the amount of reducing agents present in the solution and the reaction conditions.