Question

what is conserved during a chemical reaction????

Answer 1

mass

Answer 2

If I use a kilogram of "rocket fuel" (1:9 ratio of liquid hydrogen to liquid oxygen) to launch a rocket, I wind up with a kilogram of water:
\[112g\space H_2+888g\space O_2\rightarrow1000g\space H_2O\]
This is the law of conservation of mass.
http://en.wikipedia.org/wiki/Conservation_of_mass