Chlorine forms from the reaction of hydrochloric acid with manganese(IV) oxide. The balanced
equation is: MnO 2 + 4HCl → MnCl 2 + Cl 2 + 2H 2 O
Calculate the theoretical yield and the percent yield of chlorine if 86.0 g of MnO 2 and 50.0 g of HCl
react. The actual yield of Cl 2 is 20.0 g.

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.

answeridentity;

c. 4.54 x 10–12 j happens to be correct