In: Chemistry
From the ΔE given for 25ºC, calculate ΔH in kJ at the same temperature for the reaction: C2H6 (g) + 7/2 O2 (g) → 2CO2(g) + 3H2O (l) ΔE = -1553 kJ
we have relation H = E + PV
dH = dE + PdV + VdP , In chemical reaction P is constant , hence dP= 0
hence dH = dE + PdV
we find PdV , In reaction total gas moles removed = product gas moles - reactanat gas moles
= 2-1-1-7/2 = - 1.5 = dn
we have PV = nRT , differneatiating both sides we get PdV + VdP = dn x R x T
here VdP = 0 , R , T are constants ,
hence PdV = dn x R x T where T = 25C = 25+273 = 298 K
= -1.5 mol x 0.08206 liter atm/molK x 298 K
= -36.7 atmliter
= -36.7 x 101.325 J ( 1atmliter = 101.325 J)
= -3717 J = -3.717 KJ
now dH = dE + PdV
dH = -1553 KJ - 3.717 KJ
= - 1556.7 KJ