What Is the Structure and Stability of the S4N4 Compound?

[needhelpperson]

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

 

[GCT]

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.

 

[ravenprp]

a) The empirical formula can be calculated by converting the percentages to grams and dividing by the molar mass of each element. This gives a ratio of S:N of 2.29:1. The molecular formula can be determined by dividing the molecular mass (184.3 g/mol) by the empirical formula mass (78.1 g/mol), giving a ratio of 2.36:1. This can be rounded to give the empirical formula of S2N and the molecular formula of S4N4.

b) The bond distances in the ring can be calculated by using the bond length of the S-S bond in the S8 ring (2.05 A) and the fact that all the bonds in the ring are of the same length. This means that the bond distance between each sulfur and nitrogen atom is approximately 2.05 A.

c) To estimate the average bond enthalpy in the compound, we can use the enthalpy of formation (480 KJ/mol) and the enthalpy of formation of S(g) (222.8 KJ/mol). The difference between these two values (257.2 KJ/mol) represents the energy required to form the bonds in the compound. Since there are 4 S-S bonds and 4 N-N bonds in the ring, this energy can be divided by 8 to give an average bond enthalpy of approximately 32 KJ/mol.

As for the Lewis dot diagram, it is possible for some bonds to be double bonds while others are single bonds in a ring structure. This is due to the delocalization of electrons in the ring, which allows for some bonds to be stronger than others. This is also why the bond distances in the ring are all the same length, as the electrons are spread out evenly throughout the ring structure.

In regards to the NH3 being a liquid, the bond enthalpy values given are usually for gaseous molecules. However, for this calculation, we can assume that the bond enthalpy for NH3 in liquid form would be similar to that of gaseous NH3, as the difference in energy would be small.