The Equation for this reaction is as follow,
2 Cr(ClO₃)₃ → 2 CrCl₃ + 9 O₂
According to eq,
604.68 g (2mole) of Cr(ClO₃)₃ produces = 288 g (9 moles) of O₂
So,
146.5 g of Cr(ClO₃)₃ will produce = X g of O₂
Solving for X,
X = (146.5 g × 288 g) ÷ 604.68 g
X = 69.77 g of O₂