-calculez masa de clorat pur
p=m,px100/m,
90/100=m,p/73,5----> m,p=66.15g
M,KClO3= 122,5g/mol
2mol..................................3mol
2KClO3----------> 2KCl + 3O2
2x122,5g...........................3x32g
66,15................................x=m,O2= 66,15x3x32/ 2x122,5=........calculeaza !!!