The amount of the substance of the formed oxygen, during the decomposition of 490 g of berthollet salt in moles?

According to the condition of the problem, we compose the reaction equation:
2KClO3 = 3O2 + 2KCl – decomposition reaction, oxygen and potassium chloride are formed;
Let’s determine the molecular weights of substances:
M (KClO3) = 39.1 + 35.5 + 16 * 3 = 122.6 g / mol;
M (O2) = 16 * 2 = 32 g / mol;
Let’s calculate the number of moles of Berthollet’s salt:
Y (KClO3) = m / M = 490 / 122.6 = 3.99 mol = 4 mol;
Let’s make the proportion:
4 mol (KClO3) – X mol (О2);
-2 mol – 3 mol from here, X mol (O2) = 4 * 3/2 = 6 mol;
Answer: during the reaction, oxygen was released in the amount of 6 mol.