Hello everybody,

I'm told that potassium permanganate is dissolved in an aqueous buffer of ammonia and ammonium at equal concentrations (1M), and treated with 1M sodium hypochlorite, the permanganate ion is reduced to insoluble manganese dioxide as the hypochlorite ion is oxiddized to perchlorate ion.

I have the notes to the solution of the problem, but I noticed that he considered the solution to be acidic?

Why???
The buffer should have no affect on pH and OCl^- is a weak bronstend lowry base. So why wouldn't the solution be basic?

A buffer of NH3 and an ammonium salt SURELY is basic. That is more profound than OCl^-. Furthermore, if permanganate is reduced to MnO2, that only goes to MnO2 in basic solution. In acidic solution the permanganate goes to Mn^+2. I suspect someone just wrote acidic. I agree with you that it should be a basic solution (or at least neutral).

Thanks Dr.Bob, I'll bring that to my proffesor's attention

Hello! It seems like you have doubts regarding the acidity of the solution. Let's break down the reaction and discuss the possible reasons for considering the solution as acidic.

In the given reaction, potassium permanganate (KMnO4) is dissolved in an aqueous buffer of ammonia (NH3) and ammonium (NH4+) at equal concentrations. Then, it is treated with sodium hypochlorite (NaOCl).

The reaction can be summarized as follows:
2 KMnO4 + 3 NaOCl + 3 NH3 β†’ 2 MnO2 + 3 NaCl + 3 H2O + 3 NH4+

Generally, the buffer composed of ammonia and ammonium ions acts to resist changes in pH. This is because NH3 can accept a proton to form NH4+ and maintain the pH level. However, in this case, the reaction involves not only ammonia and ammonium ions, but also sodium hypochlorite, which is the key factor in determining the acidity of the solution.

Sodium hypochlorite (NaOCl) is derived from hypochlorous acid (HOCl), which is a weak acid. In water, HOCl partially dissociates to form hypochlorite ions (OCl-) and hydrogen ions (H+). The equation can be represented as follows:
HOCl β‡Œ H+ + OCl-

In the given reaction, sodium hypochlorite (NaOCl) is being reduced, meaning it is losing electrons and the oxidation state of chlorine is changing. This implies that the hypochlorite ions (OCl-) are being converted into perchlorate ions (ClO4-).

The oxidation reaction for hypochlorite ions in water can be represented as follows:
2 OCl- + 4 H+ β†’ 2 ClO4- + 2 H2O

Since hydrogen ions (H+) are involved in this oxidation reaction, it has an acidic nature. Therefore, the overall reaction, which involves the oxidation of hypochlorite ions, suggests that the solution is acidic.

It's important to note that the buffer composed of ammonia and ammonium ions will help in maintaining the pH within a certain range, but the presence of the acidic hypochlorous acid (HOCl) and the involvement of hydrogen ions (H+) in the oxidation reaction justify considering the solution as acidic.

I hope this explanation clarifies why the solution is considered acidic in the given reaction. If you still have questions or need further clarification, I'm here to assist you!