These are the two most common units for concentration, and unfortunately they're also the most confusing since they're exactly the same word except for one letter. This video explains how to calculate both, how to spot the difference, how they are handled differently in the lab, and the types of questions your teacher is likely to put on the test.
Mass Percentage, ppm, Mole Fraction, etc
This video covers all the obscure units of concentration that you'll see on the test in this chapter, but then never see again until the final or AP exam.
This video covers a particular type of problem that every teacher asks. There are two versions. One asks you to calculate the concentration of a solution created by diluting an existing solution with water, usually using the equation M1V1=M2V2. The other asks you the concentration of a solution formed by combining two solutions of different concentrations.
If you do not have an account, you should get one, because it is awesome! You can save a playlist for each test or each chapter, and save your "greatest hits" into a "watch right before the final" list (not that we recommend cramming, but when in Rome...)