I have not personally watched all the videos on the sites linked below, but I like the way the site is laid out by topics so a student can select some videos to help with any troublesome topic in the ACE Chemistry course.

Another potential site for help is Khan Academy

Chemistry 1125 Video Help

Stoichiometry is a challenging concept in Chemistry, but it is important to understand. These lessons were put together quickly to help a student in Mexico who asked for some tutorials to help with pages R-V in PACE 1125. I used my smartphone on a little tripod — sorry the angle cut off my head sometimes! (The orange tie was a Christmas gift from my grandson)