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Oh please help, only 3 hours left

  1. Oct 18, 2004 #1
    Under special conditions, sulfur reacts with anhydrous liquid ammonia to form a binary compound of sulfur and nitrogen. The compound is found to consist of 69.6% S and 30.4% N. Measurements of its molecular mass yield a value of 184.3 g/mol. The compound occasionally detonates on being struck or when heated reapidly. The sulfur and nitrogen atoms of the molecule are joined in a ring. All the bonds in the ring are of the same length.
    a) Calculate the empirical formula and molecular formulas for the substance.
    b) Predict the bond distances between the atoms in the ring (Note: the S-S bond distance in the S8 rign is 2.05 A)

    c The enthalpy of formation of the compound is estimated to be 480 KJ/ mol. The Hf of S(g) is 222.8 KJ/mol. Estimate the average bond enthalpy in the compound.

    i did a but i drew the lewis dot diagram out with the S4N4 and it turned out there were 2 double bonds while the rest were single bonds. How does that work if the bond distances in the ring are the same length?

    as for c i have no idea how to do this.

    i think the formula is this 2 S2(g) + 4 NH3(l) -> S4N4 + 6 H2(g)

    I'm given the N-H bond enthalpies as 391 KJ/mol but that's according to gas. NH3 is a liquid. How am i suppose to solve this. Please help. thanks
  2. jcsd
  3. Oct 19, 2004 #2


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    Here are some hints (for one, procrastinating is a bad idea for most people)

    b) possibly due to resonance, meaning that the bond lengths are somewhat the average between a double bond and single bond between the two different elemets.

    b) the enthalpy of formation for some of the compounds in the equation is 0, from this you should be able to figure it out. Also, you can see that the reaction imposes that all of the N-H bonds be broken.
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