Question

of exhow many grams of no2 can be produced by the reaction of excess o2 with 19.8 of no

Answer 1

Here is an worked example. Just follow the steps. I would learn how to spell chemistry, how to write formulas no spells "no" (the opposite of yes) to me. Finally, I would learn to start sentences with a capital letter and end them with a period. You will get more answers that way.
http://www.jiskha.com/science/chemistry/stoichiometry.html

Post your work if you get stuck.