Pt. CH4 avem
ΔrHcomb. = -802 kJ/mol cand s-a format apa gazoasa (la 25oC / 1 atm)
ΔrHcomb. = -890 kJ/mol cand s-a format apa lichida (la 25oC / 1 atm)
datele de mai sus le-am gasit tabelate
Put. calorica sup.
Qsup. = 1000xΔrHcomb./22,4 pt. comb. gazosi (la 0oC / 1 atm)
PV = nRT => n = PV/RT = 1x1000/0,082x273
= 44,67 kmoli
V = nRT/P = 44,67x0,082x(273+25)/1
= 1092m3 CH4 (rotunjit)
=> Qsup. = 1092xΔrHcomb./22,4
= 1092x890/22,4 = 43387,5 kJ
Qinf. = 1092xΔrHcomb./22,4
= 1092x802/22,4 = 39097,5 kJ
Pt. n-C6H14 avem
trebuiesc calculate ΔrHcomb. cand se formeaza H2O(g) si ΔrHcomb. cand se formeaza H2O(l), pa baza valorilor H°f date in tabelele de la sfarsitul manualului (daca esti in cls. a 12-a)
H°f(n-C6H14)(l) = -199 kJ/mol
H°f(CO2)(g) = -394 kJ/mol
H°f(H2O)(g) = -242 kJ/mol
H°f(H2O)(l) = -286 kJ/mol
valorile le-am rotunjit pt. usurarea calculelor
C6H14 + 19/2O2 --> 6CO2 + 7H2O(l)
=> ΔrHcomb.(H2O)(l) = -4167 kJ/mol
C6H14 + 19/2O2 --> 6CO2 + 7H2O(g)
=> ΔrHcomb.(H2O)(g) = -3859 kJ/mol
avand combust. lichid calculam
miu.C6H14 = 86 g/mol
Put. calorica sup.
Qsup. = 1000xΔrHcomb./miu pt. comb. lichizi/solizi (la 0oC / 1 atm)
= 1000x4167/86 = 48453,5 kJ
Qinf. = 1000xΔrHcomb./82
= 1000x3859/82 = 47061 kJ
