Question

O substanta organica A contine in molecula C, H ,O si are masa moleculara 72. Prin arderea completa a 144g de substanta , se consuma 1232 l de aer (20%O2) si rezulta 144g H2O. Care este formula moleculara a substantei?

Answer 1

CxHyOz      12x + y + 16z = 72
CxHyOz + 0,5 ·(2x+0,5y - z) O2 = xCO2 + y/2 H2O
n CxHyOz = 144/72 = 2moli
nO2 = 0,2·1232/22,4 = 11 moli      2x + 0,5y - z = 11
nH2O = 144/18 = 8 moli ⇒ nH = 16 (in 2 moli subst/)⇒ y =8
12x + 16z = 64    3x + 4z = 16
                               2x - z = 7
                            -----------------
                              11x = 44  x = 4;    z = 1         C4H8O