What assumption did you make about the reaction of KMnO4 solution in those determinations where temp didn't change to allow k to be a constant?
You need to clarify what you did. I have no idea what you're talking about.
In determinations where the temperature doesn't change, it can be assumed that the reaction of the KMnO4 solution is independent of temperature. This means that the rate constant (k) remains constant throughout the reaction, regardless of any temperature fluctuations.
To answer your question, I would need more context about the specific reaction you are referring to. However, I can explain a general concept related to assumptions in chemical reactions and temperature.
In many chemical reactions, temperature is an important factor that affects the reaction rate. According to the Arrhenius equation, the rate constant (k) of a reaction is temperature-dependent. As temperature increases, the reaction rate generally increases as well.
Now, if you mentioned that in certain determinations with a KMnO4 solution, the temperature did not change, it suggests that the reactions were carried out at a constant temperature. Assuming the temperature remains constant, it implies that the rate constant (k) is also constant for those specific determinations.
However, it is essential to note that this assumption might not hold in all cases. There could be other factors apart from temperature that affect the reaction rate, such as concentration, pressure, catalysts, or the presence of other reactants or products. It is always crucial to consider the specific details and conditions of the reaction to fully evaluate the assumptions made in its determination.