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.

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

that's it!

if you need further assistance, let me know: )

~ trueboss72

im pretty sure its b