Answer:

Explanation:
Hello,
In this case, given the balanced reaction:

We can see a 2:4 mole ration between permanganate ion (118.9 g/mol) and manganese (IV) oxide (86.9 g/mol), that is why the resulting mas of this last one turns out:

Best regards.
12, electrons dont have mass. only protons and neutrons do
The unit cm3 is used to express a cube using cm