Since 1 molecule of `KNO_(3)` contains 3 atoms of oxygen , 1 mol of `KNO_(3)` contains 3 mol of oxygen atoms .
`therefore` moles of oxygen atoms = `3 xx ` moles of `KNO_(3)`
`= 3 xx (1000)/(101) = 29.7` (Molecular mass of `KNO_(3) = 101`)
`therefore` mass of oxygen = number of moles `xx` atomic mass = `29.7 xx 16 g = 475 . 2 g `
