 So, let's continue along with the same problem that we just did about the chemists making the acidic solution and see, well, what is the pH of that solution? Okay, so what is the equation for pH, guys? So the negative log of the concentration of hydrogen, okay, so remember that equation. All you have to do, and again, the units don't come out pH is unitless, okay? So watch out about that. So negative log, and I'll just put in here 3.0 times 10 to the negative 4, okay? No units, just so I won't confuse myself. And then you've got to find your log button on your calculator. You don't know where it is already, okay? So, log. And like you should imagine, you should get something around pH 4, okay? So if you're getting somewhere, the units are around 4, then you get something right, okay? So, here, there's a weird rule whenever you take a log, you can increase the number of significant figures, so this is going from 2 to 3, okay? So when you go the other way, you go from 3 to 2, okay? So that's just a big, big rule you've got to remember. So the answer to this would be 3.5, so that's the pH. So just remember that you increase it when you take the log and decrease it if you go there. Are there any questions on that one? Questions? Questions. Okay, good job.