Question

1) Calculati entalpia de formare standar a etanului (delta f Hc2h6) cunoscand urmatoarele constante termochimice:
delta f Hco2= - 393.5 kj/mol, delta f Hh2o = -285.5kj/mol.
2) Calculati caldura degajata la arderea unui volum de 1 dm (cub) etanol (densitatea=0.79g/mol) cunoscand efectul termic l relatiei:
C2H5 - OH(l) + 3O2(g) ---> 2CO2(g) + 3H2O(g)

Answer 1

1. r1:   2C+3H2---> C2H6..........................Δ..H,f=?
    r2:    C+O2----> CO2..............................ΔH,f=-393,5kj/mol
    r3:     H2+1/2O2--> H2O.........................Δ.H,f= -285,5kj/mol
r1= 2 r2+3 r3...........................ΔHf= 2molx(-393,5kj/mol)+3molx(-285,5kj/mol
                                                       calculeaza !!!!!

2.ro=0,79g/ml=m/v,    v= 1dmcub=1 l=1000ml---> m= 79og
M, alcooletilic= 46g/mol
n=m/M;n= 790g/46g/mol
1mol............................................ΔH (trebuie sa-l cunosti in kj/mol)
790/46mol...........................................x