Since the dawn of time, students have been given pop quizzes by teachers who like to give surprise assessments. If you're one of these teachers, here are some of my favorites.
On the other hand, let's say that instead of basing student grades on this you decide instead to use these assessments as ungraded practice activities that allow your students to figure out what they already know and what they have left to learn. These pop quizzes are good for that, too.
Here's my pitch: I've written a number of chemistry books (the most popular is "The Complete Idiot's Guide To Chemistry" from Alpha/Penguin) and have spent lots of time in the classroom using these activities with my own students. Because these pop quizzes are free, upload them without any risk and see if you like them. If so, cool - use them. If not, you've lost nothing. Give it a shot!