Question

The amount of oxygen formed when 12.26 g of KClO3 is heated

Answer 1

2KClO3--->2kcl+3O2

Then,

245 kclo3----->96 o2

12.26 kclo3---> x

Cross multiply,

X=(96*12.26)/245

=>4.8grams

please like this because i am only in 7th standard.

Answer 2

Reaction for the decomposition is,

       2KClO₃ --------⇒ 2KCl +  3O₂

Molar mass of KClO₃ = 39 + 35.5 + 48 = 122.5 g/mole.

Molar mass of KCl = 39 + 35.5 = 74.5 g/mole.

Molar mass of O₂ = 32 g/mole.

∵ 2 moles of KClO₃ forms 1 mole of Oxygen.

∴ 2 × 122.5 g of KClO₃ forms 32 g of Oxygen.

∴ 1  g of KClO₃ forms 32/245 g of Oxygen.

∴ 12.26 of KClO₃ forms 32/245 ×  12.26 g = 1.60 g of Oxygen.

Hence, the mass of the Oxygen evolved in this case is 1.6 g.

Hope it helps.