Pyridine (C5H5N) and pyrazine (C4H4N2) have structures similar to benzene. Both compounds have structures with 6 atoms in a ring. Draw Lewis strcutures for pyridine and pyrazine showing the two most common resonance forms. The N atoms in pyrazine are directly opposite each other in the ring with 2 carbons between them in either direction. Indicate resonance with a double headed arrow between structures. Draw the Lewis structures with the formal charges minimized.

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answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.

> b takes place in the gas phase in an isothermal tubular reactor. the feed is one mole of a per one mole of c, an inert. the entering temperature and pressure are 427°c and 10 atm, respectively. the gas constant r = 0.08206 atm · l/mol · k.