Calculate how much oxygen can be obtained by decomposing potassium permanganate with a mass of 395 g.

1. Let’s write down the equality of chemical interaction:

2KMnO4 = K2MnO4 + MnO2 + O2.

2. Determine the chemical number of decomposed potassium permanganate:

n (KMnO4) = m (KMnO4) / M (KMnO4) = 395 g / 158 g / mol = 2.5 mol.

3. According to the interaction equation, we determine the chemical number, and then the volume of released hydrogen (Vm is the molar volume, constant equal to 22.4 l / mol):

n (O2) = n (KMnO4) / 2 = 2.5 mol / 2 = 1.25 mol.

V (O2) = n (O2) * Vm = 1.25 mol * 22.4 L / mol = 28 L.

Result: V (O2) = 28 liters.