[Borek]

3.0372 g of a mixture containing BaCO₃ and BaO₂ was dissolved in an excess of a diluted sulfuric acid. Collected precipitate weighed 3.200 g. Filtrate was quantitatively transferred to a 250 mL flask and filled to the mark. Titration of the 25.00 mL of the solution with 0.0200 M permanganate required 9.14 mL of the solution.

What was the composition of the mixture?

[Rutherford]

Tried this one. I got that n(H₂O₂)=4.57*10^-3moles. When I assumed that the whole BaO₂ reacted (its n is the same as of hydrogen-peroxide) I couldn't get a result that satisfies the two given masses. Then I assumed that not all BaO₂ reacted with H₂SO₄, and I got a system of two equations that couldn't be solved (got negative number). A lower mass of the original mixture could give good answers.

[Borek]

A lower mass of the original mixture could give good answers.

3.0372 g of a mixture containing BaCO₃ and BaO₂

It doesn't say "containing only"...

[Rutherford]

Then all BaCO₃ and BaO₂ precipitated. I got 59.44% of BaCO₃ and 25.43% of BaO₂.

[Borek]

That was probably much easier than the forum upgrade 

[Rutherford]

Heh, would be harder if not all barium peroxide precipitated and the mixture contained only the carbonate and peroxide (with lower mass), but it was good.

[123456789]

Sorry this is over, but just wondering is the reaction of KMnO4 and H2O2

This: 2MnO4–(aq) + 3H2O2(aq) → 2MnO2(s) + 2H2O(l) + 3O2(g) + 2OH–(aq)

Or this: 2MnO4- + 5H2O2 + 6H+ → 2Mn2+ + 5O2 + 8H2O

It is acidic condition, so it should be (2) right? However, some (reputable) sources also claim it to be (1). So which is the correct one? When do you use the 1st eqn then? Thanks!

[Borek]

Titration conditions are selected in such a way 2^nd equation describes exactly what is happening.

As a rule of thumb permanganate in acidic conditions gets reduced to Mn²⁺, in neautral to MnO₂, in basic to MnO₄^2-. As every rule of thumb it doesn't have to be true always.