Yes when a firework goes into the sky it releases chemical potential energy which is then changed into kinetic energy
Two things that store chemical energy are coal, and wood cause when you have a fire you have to get the chemicals from somewhere to keep your fire live.
Bleach would increase the pH because Bleach is a basic substance with a pH of about 12
Soda would lower the pH because the pH of sodas is somewhere around 2.5 (this is for coke, other sodas are a bit different)
I would suggest you to use this instead.
Just place the known substance for example O2 Oxygen as they are asking you, and see where the diagram takes you.
So the answer would be 2 because you’d look at the coefficients of the balanced equation up there. H2O
I hope that was helpful, if you have more questions please ask!