In a chemical equation, which symbol should be used to incate that a substance is in solution?
(s)
(g)
(i)
(aq)

It's l if you mean liquid

NO  react  with  oxygen  to  form   NO2 
  that  is 2NO  +O2 --->2NO2
from   the  reaction  above two  moles of  NO  react  with  one  mole of  O2  to  form two  moles  of  NO2
The  reacting  ratio  of  NO  to NO2  is  2:2    or  1:1    in  simple  terms
since   ratio  is  1:1  the  moles  of  NO  reacted  is  also  4.67moles