acid acetic ------> CH3 - COOH
-se afla masa molara
M= 2.12 + 4 + 2.16=24 + 4 +32
=60-------> 60g/moli
60 g acid acetic-------------24 C---------4g H----------32g O
100g -------------------------------x--------------y-----------------z
x=100. 24 : 60=40 % C
y= 100. 4 : 60=6,6% H
z=100.32 :60=53,4 % O