Potassium chlorate (used in fireworks, flares, and safety matches) forms oxygen and potassium chloride when heated. KClO3 (s) → KCl (s) + O2 (g) [unbalanced] What mass of oxygen gas is formed if 26.4 g of potassium chlorate decomposes completely?

10.56g

Explanation:

From the reaction equation, we can see that it is unbalanced. In the balanced state, 2 moles of KClO3 will yield 3 moles oxygen.

Let's calculate the actual number of moles now. We first divide the mass of the KClO3 by the molar mass. Molar mass of KClO3 = 39 + 35.5 + 3 (16) = 122.5g/mol

The number of moles is thus 26.4/122.5 = 0.22 mole

If 2 moles KClO3 gave 3 moles O2, this means 0.22 moles will give (0.22 * 3) / 2 = 0.33 mole

To calculate the mass of oxygen formed, we multiply the molecular mass of oxygen molecule by the number of moles

The molecular mass of oxygen molecule = 16 * 2 = 32g/mol

The mass formed = 32 * 0.33 = 10.56g