Molar mass :
O₂ = 16 x 2 = 32.0 g/mol
KClO₃ = 39 + 35,5 + 16 x 3 = 122.5 g/mol
Chemical equation:
2 KClO₃(s) = 3 O₂(g) + 2 KCl(s)
2 x ( 122.5 g KClO₃) ---------------------- 3 x ( 32.0 g O₂ )
3.450 g KClO₃ ----------------------------- ( mass of O₂)
mass of O₂ = 3.450 x 3 x 32.0 / 2 x 122.5
mass of O₂ = 331.2 / 245
= 1.35 g of O₂
hope this helps!
