To obtain oxygen, a seven-gram sample of natural mercury (II) oxide with a concentration of foreign impurities of 69%

To obtain oxygen, a seven-gram sample of natural mercury (II) oxide with a concentration of foreign impurities of 69% was thermally decomposed. How many liters of oxygen were obtained if the practical product yield was 70% of the theoretically possible?

Let’s write the reaction equation:
2HgO = 2Hg + O2
find the mass of pure mercury oxide 700 * 0.31 = 217 g
n = m \ M = 217 \ 201 = 1 mol
according to the reaction equation n (O2) = 0.5 mol
V (O2) = 0.5 * 22.4 = 11.2 l is the theoretical volume
practical volume: 11.2 * 0.7 = 7.84 l