The heat of formation of liquid hydrazine (N 2 H 4 ) is 50.63 kJ/mol. Use tabula
ID: 786468 • Letter: T
Question
The heat of formation of liquid hydrazine (N2H4) is 50.63 kJ/mol. Use tabulated data for other heats of formation.
The tolerance on each question is only 0.03 kJ, so express all answers to 0.01 kJ.
H = kJ q = kJ w = kJ E = kJ Determine delta H, q, w, and delta E at 298 K and 1 atm for the complete reaction of 8.560 g of N2O4. N2O4(g) + 2N2H4(l) rightarrow 3N2(g) + 4H2O(l). The heat of formation of liquid hydrazine (N2H4) is 50.63 kJ/mol. Use tabulated data for other heats of formation. The tolerance on each question is only 0.03 kJ, so express all answers to 0.01 kJ.Explanation / Answer
The moles of dinitrogentetroxide is 8.5/92 = 0.0923 mols
The number of mole of hydrazine need to react completely is 2 x 0.0923 =.1847
the number of moles of water will form is 4x 0.0923 = .3692.
The enthalpy of this reaction is .3693 x the heat of formation of liquid water(look it up) -( .0923 x the heat of formation of dinitogentetroxide +.1847 x the heat of formation of hydrazine) ( you don't count N2 becase it is and element and by defintion Delta H formation is 0)
Plug the numbers in and you have delta H for this reaction
which is the same as q
w is the work of expansion that must be done at constant pressure.
Since two more moles of gases are produced than you start with ( or .186 moles of gases are produced because the dintrogentetroxide is the limiting reagent.
so the w = P deltaV = nRT = .186mol( 8.314 (Joule/(Kmol))298K = 1.546Kj
E = enthalpy of reaction + (work done on the atmosphere as the gas expanded)
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