Răspuns :
[tex]2KClO_3 \to 2KCl+3O_2 \\ m_{KCLO_3}=245 \ g \\ \nu=\frac{m}{M} \\ M_{KClO_3}=39+35,5+16\cdot 3=122,5 \ g/mol \\ \Rightarrow \nu_{KClO_3}=\frac{245 \ g}{122,5 \ g/mol}=2 \ moli; \\ KClO_3 \to \frac{2}{2}; \ \ O_2\to \frac{x}{3} \\ \Rightarrow \frac{2}{2}=\frac{x}{3} \ \Rightarrow x=3 \\ \Rightarrow \boxed{\nu_{O_2}=3 \ moli}; \\ m_{O_2}=\nu_{O_2}\cdot M_{O_2}; \\ M_{O_2}=16 \cdot 2=32 \ g/mol \\ m_{O_2}=3 \ moli \cdot 32 \ g/mol \\ \Rightarrow \boxed{m_{O_2}=64 \ g}[/tex]