MKClO₃=AK+ACl+3AO=39+35,5+3*16=122,5g/mol
MO₂=32g/mol
puritatea= masa pura/masa impura*100 => masa pura=puritatea*masa impura/100 = 90*272,2/100=244,98g KClO3
2KClO₃ ⇒ 2KCl + 3O₂
2*122,5 KClO₃........................3*32g O₂
244,98g KClO₃............................xg O₂
x=3*32*244,98/2*122,5=96g O₂
n=m/M=96/32=3 moli O₂
n=V/Vm⇒V=n*Vm=3*22,4=67,2 L O₂
1 mol O₂.........................6,023*10^23 molecule
3 moli O₂........................x=3*6,023*10^23 molecule
R: a,b,c