 Ok, so let's try this problem. It says that we convert the hydrated zinc 2 plus ion to the more stable zinc ammonia 4 2 plus ion by mixing 50.0 liters of 0.0020 molar of the hydrated zinc 2 plus ion and 25.0 liters of 0.15 molar ammonia. What's the final concentration of the hydrated zinc 4 2 plus ion if the kf of the zinc ammonia complex is 7.8 times 10 to the 8. Ok, so that's a big equilibrium constant. So it's different than what we've been used to seeing. So the first thing we're going to need to do is convert these two to their new molars. Ok, so in order to do that, so that was the initial. Let's do the final concentration. So that's going to be all 1 liter times 15.0 liters divided by 15.0 liters plus 25.0 liters of molar. So that's the final concentration of that. So let's do the same thing to ammonia now. The next thing we're going to want to do is write out the formation equation. So I'm going to erase all the work here and just rewrite these concentrations here. So 1.3 times 10 to the 8 is 30 molar. We're not sure how many ammonia is yet, so we've got to look at what the final complex is. We need an nH3, 4 to the plus. So when we do that, we know there's going to be 4 there. Plus, of course, now 4 H2O. And then we have the kf of that equals 7.8 times 10 to the negative 3. Let's do an ice table. So here, what's our concentration? 1.3 times 10 to the negative 3. So we're going to subtract 1.3 times 10 to the negative 3. And actually, we're subtracting approximately that much. Just like that last problem, it's not all the way. So when we do that, we're actually going to find x. That's what we're looking for. Actually, it's the concentration that's left. If you remember what the problem said. I know you guys don't have it written down in front of you. You just have to believe. So we have this here, 5.0 times 10 to the negative 2. And we're going to subtract from this 1, 1.3 times 10 to the negative 3. But we've got to multiply that by 4. Because there's 4. Let's do that. 10 to the negative 2. So this one before was 0. And then we're going to add 1.3 times 10 to the negative 3. So it's going to be 1.3 times 10 to the negative 3. So we have the KF value. Let's figure out what the KF equation is. So the KF equation is this. So the KF equation, as you might imagine, is this. Concentration of zinc with the ammonia is on it. Divided by the hydrated zinc ion, ammonia to the force. So let's go ahead and start. X there, concentration of zinc, hydrated ion on the left, is going to equal the ammonia complex. Concentration divided by KF times the concentration of ammonia to the force. Can everybody get to that point? OK, so now it's just plug and check. So at the top, it's going to be what do we have? 1.3 times 10 to the negative 3 divided by KF, 7.8 times 10 to the 8th. And that's multiplied by ammonia, 4.5 times 10 to the negative 2 to the force. As you might imagine, a very small number. Because we would have expected it to be around 0. Because we took it all out. But there's still a small amount left. And that small amount is equivalent to 4.0 times 10 to the negative 7 mole. So that's how much of the hydrated zinc ion is still left. OK, are there any questions about that one? Yeah, what's that? Well, like I said, there's still a little bit of it left. It doesn't all just react. It's just like that last problem we did. I know we had a lot of questions about is 10 to the negative 12 the same as 0? Yes, in our case it's approximately the same. But if you wanted to actually calculate that number, we can do that. And we did. Are there any other questions about that? OK, wonderful.