1. Calculate the volumes of the samples used in Procedure step 2. Record the calculated volumes in Table 2.2. Why could we not find the volume of the bolt by this method? 2. How did you find the volume of the PE rod using the displacement method? Note: 1 cm3 = 1 mL. Because PE floats, push the rod under the water with a very small object, such as a pin, and volume of the pin is negligible and can be ignored. 3. Except for the bolt, note the difference between the calculated volumes and the volume found by the displacement method. Which method is more accurate? Why?

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)

  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-

answerca air mass;