21.7 g of mercury (II) oxide was decomposed. Calculate the amount of oxygen released.

The reaction equation for the thermal decomposition of mercury (II) oxide:

2HgO (t) = 2Hg + O2 ↑

Let’s find the amount of substance HgO:

v (HgO) = m (HgO) / M (HgO) = 21.7 / 217 = 0.1 (mol).

According to the reaction equation, from 2 mol of HgO, 1 mol of O2 is formed, therefore:

v (O2) = v (HgO) / 2 = 0.1 / 2 = 0.05 (mol).

Thus, the released amount of oxygen is:

v (O2) = 0.05 (mol).

Answer: 0.05 mol.