 So, molarity problem, it says hydrochloric acid is sold commercially as 12.0 molar aqueous solution. How many moles of HCl are in 300 mils of the 12 molar solution? Okay, so it says the concentration, so the molarity against us, right, is 12.0 molar. If you want to put C for concentration, that's okay, but for ranian, remember 12.0 molar, right, that's a derived unit, 12.0, if you like to do this, it's good for you to do, okay, moles per one liter. And it also told us that we have a volume of HCl, this is the molarity of HCl, the volume of HCl was 300 milliliters, so we have 300 milliliters of HCl, and for every 12 moles of HCl, we have one liter of solution of the HCl solution. So, notice these are in milliliters, right, so these are in liters, so we want to convert milliliters to liters, so I wanted to know how many moles were in that many liters, well, we've got this conversion factor, HCl canceled, so let's just do it, 800 divided by 1000 times 12, the three sig figs, 3.6. And this is moles, so that's how many moles of HCl are in, 300 mils of a 12 molar HCl solution. Everybody okay with that? Questions on doing something like that? Again, this is just another conversion factor that you guys know, and molarity equals moles per liter.