For the reaction, calculate how many moles of the product form when 0.046 mol of O2 completely reacts. Assume that there is more than enough of the other reactant.
2Ca(s)+O2(g)→2CaO(s)
Express your answer using two significant figures.

0.023 moles of CaO.

Explanation:

The balanced equation tells us that we'll get 2 moles of CaO for every one mole of O2.  Since we have 0.046 moles of O2, we'll get 0.023 moles of CaO.  (2 sig figs)

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.