How many Liters O2will form from the decomposition of potassium chlorate (KClO3) if 6.4 x 1024 formula units KClO3 are used?

Answer 1

2KClO₃ ==> 2KCl + 3O₂ ... balanced equation

This tells us that 3 moles of O₂ will form from 2 moles of KClO₃. We are given 6.4x10²⁴ form. units of KClO₃ so convert that to moles. From moles of KClO₃ we can find moles of O₂ and if we assume this is at STP, then 1 mol O₂ = 22.4 L.

moles KClO₃ = 6.4x10²⁴ form.units x 1 mol/6.02x10²³ form.units = 10.6 moles KClO₃

moles O₂ = 10.6 mol KClO₃ x 3 mol O₂ / 2 mol KClO₃ = 15.9 moles O₂

Liters O₂ = 15.9 moles O₂ x 22.4 L / mole = 357 L = 360 liters of O₂ (2 sig. figs.)