Khan Academy – great site to find videos, practice questions and quizzes on specific chemistry topics.
Sophia Learning - another great free site to find videos, practice questions and quizzes on specific chemistry topics.
Crash Course Chemistry– 46 episodes of Han Green teaching introductory college-level chemistry. Great for students in grade 12. If you do not see what you are looking for on this link you can always search “crash course blank” to find other interesting topics