How many grams of kcio3 are needed to produce 5.00 of o2 at stp?

2KClO₃ → 2KCl + 3O₂

mole ratio of KClO₃ to O₂ is 2 : 3

∴ if moles of O₂ = 5 mol

then moles of KClO₃ =

                            = 3.33 mol

Mass of KClO₃ needed = mol of KClO₃ × molar mass of KClO₃

                                      = 3.33 mol × ((39 × 1) + (35.5 × 1) + (16 × 3) g/mol

                                      = 407.93 g

Maybe you should get some from your teacher and learn more so you can get your grades up and maybe study a bit more