Hydrazine (N2H4) is a fuel used by some spacecraft. It is normally oxidized by N2O4 according to the following equation:

N2H4 (l) + N2O4 (g) - >2N2O (g) + 2H2O (g)

Calculate delta Hrxn for this reaction using standard enthalpies of formation.

-476.95 Kj

Explanation:

N2H4 (l) + N2O4 (g) = 2N2O (g) + 2H20 (g)

∆Hrxn = n∆Hf (products) - m∆Hf (reactants)

Where n and m = stoichiometric coefficients of the products and reactants respectively from the balanced chemical equation, ∆Hf = standard enthalpy of formation, ∆Hrxn = standard enthalpy of reaction.

Using the following standard enthalpies of formation (you did not provide any):

N2H4 (l) = + 50.63Kj/mol; N2O4 (g) = + 9.08Kj/mol; N2O (g) = + 33.18Kj/mol; H2O (g) = - 241.8Kj/mol

∆Hrxn = [ (2 (∆Hf (N2O)) + (2 (∆Hf (H2O)) ] - [ (1 (∆Hf (N2H4)) + (1 (∆Hf (N2O4)) ]

∆Hrxn = [ 2 (+33.18) + 2 (-241.8) ] - [ (+50.63) + (+9.08) ]

∆Hrxn = [ (+66.36) + (-483.6) ] - [ + 50.63+9.08]

∆Hrxn = [ + 66.36-483.6] - [+59.71]

∆Hrxn = - 417.24-59.71

∆Hrxn = - 476.95 Kj

NOTE: Remember to use the standard enthalpies of formation given to you by your instructor if they differ from the values used herein, and follow the same procedure.