100% amestec (carbon+iod) impur .......... 80% pur
20 g amestec ............................................. m g pur
= 16 g amestec pur
notam cu a = masa de carbon
b = masa de iod
a = bx1/4 => b = 4a
=> a + 4a = 16
=> a = 16/5 = 3,2 g carbon
=> b = 4a = 12,8 g iod