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how should measurements and calculations be reported to reflect uncertainty?

See below  

Step-by-step explanation:

Measurements

Every measurement must be reported with the correct number of significant figures.

Calculations

The results calculated from a measurement are at least as uncertain as the measurement itself.

You must follow the correct significant figure rules for

You must follow the correct rules for rounding the results of your calculations.

a chemical reaction happens

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-