Question

Why make a stock solution of KMnO₄(aq) and dilute it to the concentration needed for each reaction; rather than measure out the amount of solid KMnO₄ needed for each reaction and add water to that solid to make the required concentration?

a) It ensures accurate and consistent concentrations for reactions.
b) It simplifies the process and saves time.
c) It allows for easier storage and handling of the solution.
d) It prevents contamination of the solid KMnO₄.

Answer 1

Making a stock solution of KMnO₄ ensures accurate and consistent concentrations, simplifies processes and saves time, allows for easier handling, and prevents contamination.

Step-by-step explanation:

The practice of making a stock solution of KMnO₄ and then diluting it as needed for reactions, rather than measuring out solid KMnO₄ for each reaction, is preferred for multiple reasons. Making a stock solution ensures accurate and consistent concentrations for reactions, simplifies the process thus saving time, and allows for easier storage and handling of the solution. Additionally, it helps in preventing the solid KMnO₄ from contamination.

By using a stock solution, it allows the use of molarity in stoichiometric calculations directly related to the mole unit, making it useful in chemical reactions of known stoichiometry. For example, a chemist can calculate the exact number of moles needed by using the stock solution and then dilute it to obtain the required concentration for a reaction.

Diluting stock solutions is advantageous compared to weighing small amounts of solute, which can be particularly challenging and less accurate, especially for low concentrations.