5. Water with a mass of 35.4 g is added to an empty flask with a mass of 87.432 g.
The mass of the flask and the water is 146.72 g after a rubber
stopper is added.
What is the mass of the stopper to the correct number of
significant figures.

one state would change   like louisiana to texas. thats a change

explanation:

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-

your answer would be “dry”