Which of the following equations is (are) not correctly balanced?

How is the evolution of gas indicated in a chemical equation? 
 

Are physical changes associated with energy changes? 

Give an example of a reaction in which an element combines with a compound to form a product. 

Identify oxidizing and reducing agents in the following reaction:

$2{\mathrm{H}}_2\mathrm{S}+{\mathrm{SO}}_2\to 3\mathrm{S}+2{\mathrm{H}}_2\mathrm{O}$

Identify oxidizing and reducing agents in the following reaction:

$\mathrm{Zn}+{\mathrm{CuSO}}_4\to {\mathrm{ZnSO}}_4+\mathrm{Cu}$