There is no carbon in the unknown substance A. If 19.5 g of A is annealed in the absence of air a ternary, white, crystalline compound B and a gas C form. In the presence of air gas C burns with a light blue flame. The elementary analysis of B shows 24.5 % (w/w) of carbon and 28.6 % (w/w) of nitrogen.
When annealed with carbon another ionic compound D also results in compound B, too, but without the gas. D reacts with acids to form urea among other substances. The elementary analysis of D shows 14.0 % (w/w) of carbon and 32.6 % (w/w) of nitrogen.
An aqueous solution of B reacts with an aqueous solution of iron(III) chloride to form a red solution of compound E. Compound F forms if B reacts with elementary sulfur. F reacts with an aqueous solution of iron(III) chloride, too, to form a red solution of compound G.
The reaction of an aqueous solution of E with an aqueous solution of Mohr's salt [(NH4)2Fe(SO4)2 • 6 H2O] in a molar ratio of 1 : 1 leads to the complex compound H. In H the iron cations of both oxidation states are octahedral coordinated.
a) Write down the names and the empirical formulae of the unknown substances A - H.
b) Give the equation of the reaction of D to B. Assign the oxidation states to all atoms. What is the name of this reaction?
c) Draw the Lewis structure of the anion of D.
d) Give 5 examples of existent isoelectronic compounds which have the same number of atoms as D.
e) Calculate the volume (25 °C, 1013 hPa) of the gas C which is formed in the reaction of A.
f) Which colour of compound H do you expect? Which magnetic property should H show in an inhomogeneous magnetic field? Account for your decision by using an MO scheme and its occupation with electrons.

Question

There is no carbon in the unknown substance A. If 19.5 g of A is annealed in the absence of air a ternary, white, crystalline compound B and a gas C form. In the presence of air gas C burns with a light blue flame. The elementary analysis of B shows 24.5 % (w/w) of carbon and 28.6 % (w/w) of nitrogen.
When annealed with carbon another ionic compound D also results in compound B, too, but without the gas. D reacts with acids to form urea among other substances. The elementary analysis of D shows 14.0 % (w/w) of carbon and 32.6 % (w/w) of nitrogen.
An aqueous solution of B reacts with an aqueous solution of iron(III) chloride to form a red solution of compound E. Compound F forms if B reacts with elementary sulfur. F reacts with an aqueous solution of iron(III) chloride, too, to form a red solution of compound G.
The reaction of an aqueous solution of E with an aqueous solution of Mohr's salt [(NH4)2Fe(SO4)2 • 6 H2O] in a molar ratio of 1 : 1 leads to the complex compound H. In H the iron cations of both oxidation states are octahedral coordinated.
a)	Write down the names and the empirical formulae of the unknown substances A - H. 
b)	Give the equation of the reaction of D to B. Assign the oxidation states to all atoms. What is the name of this reaction?
c)	Draw the Lewis structure of the anion of D.
d)	Give 5 examples of existent isoelectronic compounds which have the same number of atoms as D.
e)	Calculate the volume (25 °C, 1013 hPa) of the gas C which is formed in the reaction of A. 
f)	Which colour of compound H do you expect? Which magnetic property should H show in an inhomogeneous magnetic field? Account for your decision by using an MO scheme and its occupation with electrons.

aaronq · Answer

If A + heat -> B + C, How can B contain carbon when A does not?

anonymous · Answer

Yes, exactly, that's what was confusing me. O.o So, I thought maybe this was some whole new concept of chemistry.