Abalanced equation tells you the mole ratio of all reactants and products. using the chemical reaction below how many moles of nh3 are made when 3 moles of hydrogen gas are used? 2n2 + 3h2 > 2nh3

From  the  reaction  above    2  moles  of  N2  reacted  with  3  moles  of  H2  to  give  2  moles of   ammonia
THese  implies  that   the   mole  ratio  of  hydrogen  to  ammonia   is   3:2
Therefore  if   3  moles  of  hydrogen   were  used  the  moles  of  ammonia  is  therefore
(3 x2)/3=  2moles

Aphysical change is one that you can put in and remove like a ham sandwich. the stuff you put in there can be changem its not permanet. a chemical change is on that can't be change thats permanet. like when you make a cake and bake it. you can't get those ingredients back.