 Okay, so we're ready for another little working with molarity that follows up on our mole video. Molarity is used to express per liter of solvent. And for us, that solvent is usually going to be water and we'll refer to them as an aqueous. There are other solvents that can be used for solutions, alcohols, a whole host of things. But for the sample problems that we're made up in water. So molarity is expressed in terms of moles per liter. So here we have one. So if we have one mole of an atom or molecule dissolved in one liter of solvent, let's re-reviate this as one capital M is equal to one small case mol over sand for molar. Meaning a concentration and the small letter mol stands for moles molecular weight that we've already worked on. So let's start working some samples. So the question is how would you prepare one liter of a one molar aqueous solution? So here we go. The first thing is to list and put out here how many of each we have. Okay, so here we're going to try. Okay, potassium, which is 40.078 grams per mole, which is 14.007 grams per mole and 9 grams per mole. So let's write these down, 8 grams. The nitrogen was 14.007 grams, 9, 9 grams. And the oxygen here is an example of 15.999, 15.00. And some of the tutorials you'll be working with have oxygen as 16 and nitrogen. We'll be using, in this example, the three digit numbers because that's how our little interactive periodic table comes up with. So, and our third thing is to carry over how many of each we have to come up in this case with 40.078, 1447.997. And for number four down here, we're going to sum those up to grams per mole. Molecular weight of potassium nitrate in grams one mole per liter. Then that's 8 grams per liter. So we will dissolve potassium nitrate in water, bring to volume, or abbreviate that liter. All right, so we'll dissolve it and bring it to volume. So for that question, how do we prepare one liter, potassium nitrate, dissolve it in water and bring it to volume of one liter. So question two, how would you prepare one liter of three molar citric acid? Seven. So first thing, carbon, hydrogen, oxygen, and we have six oxygens. So periodic table, well there were oxygen, we're going to need that. So hydrogen is 1.00708. Our friend carbon is 12 with those values in. So we just say carbon was 12.011. Hydrogen is 8 and oxygen is 15.999. Eight of those and seven of those. So hydrogen grams. So we multiply those. So for carbon, we get 72.066 grams for 064 grams. And for oxygen, we get 13 grams. So we sum those up and we get 192 moles of citric acid. All right, so our question was how do we make a one liter of three molars, two, three grams per one liter? All right, so we multiply that. 192.123 times three is equal to 576.3 or one liter is equal to three molar. So three times one molar is equal to three molars, one, two, three. That's three grams per liter for one liter for a three molar solution. We've got a variation on that which asks us how do we prepare 500 milliliter carbonate? Molecular formula NA2CO3. So we have two of those, one of those, and three oxygens. So back at, so it's 12.011. And we need sodium, zero, and then oxygen, which we've used before, which is 15.999. And we'll get our multipliers, there's two of these. So if we do the multiplication, 22.990 times two is 45.98, 12.011. And then 15.999 grams times three is 47.9. So if we add up the individual elements, we get a molecular mass of ones per mole. So if one per liter, three molar is equal to three molars per liter. So we're wanting a three molar solution. Now, if there's three moles per mill, so how many moles are there in 500? So we've got three moles for 1,000 milliliters, moles in 500 milliliters. So we've got three moles is equal to question mark moles times 1,000 ml. Now, 1,000, we've got 500 over 1,000, which is 0.5. So we've got three moles times, so that comes out to be 1.5 moles. So we're going to need 1.5.998 grams per one mole, great, 1.5. So 105 moles is equal to unknown grams times one mole. Right, we divide them both sides and get rid of that mole on the right side. Then the moles cancel out, we divide them by 1.998 times 1.5 equals the number of grams. And that's about to be 158.982 grams is our one hammer. So we dissolve grams in water and bring divide. So what we've got, we've got 1.5 moles in 500 mills, right, is mills would be equal into three moles in one liter. So we did that in our two proportions. Right, a three molar solution is three moles per 1,000 mills, but we're only making 500. So how many moles do we need? We need 1.5 moles, and what is 1.5 moles of the sodium moles then is 158.982 grams. Okay, so this problem asks us how will we make 1.25 liters of a 608? And we have then the formula for sodium bicarbonate is Na8CO3. So you look at these problems, molecular weight of sodium bicarbonate, and then you look at the question, what is your volume, in this case 1.25 liters, and what is your... Those are the things you're looking for is how to get 1.25 liters at a concentration of 600 millimoles. So we've got sodium, hydrogen, carbon, and oxygen. So we've got 1 and 1 and 1. I've seen the periodic table often enough. You can find these sodium is 22.908. Carbon we found as 12.011 grams and 9.9 grams. Okay, so times 1 times 1 times 1. So that was going to say 22.9 grams. 1.008 grams. And 15.99 times 3 is 47.997. D4.006 grams per mole of sodium bicarbonate. If 1 molar equals 1 mole per liter equals 600 millimoles, it's always going to be expressed in terms of liter. So if it's 1 molar, it's 1 mole per liter. If it's 600 millimoles or 5 moles per liter. So when we see this 600 millimole, we can just say that 600 millimoles per millimoles per liter. And we're 1 liter. How many millimoles are cross-multiplying? So we get 600 millimoles. Times is equal to our unknown millimoles times 1 liter. We're not dividing both sides, so we get 600 millimoles. And 1.25 liter is equal to our unknown millimoles. Either, you saw me add to E there, either MOL or MOLE is okay. For the liter, we divide by 1 and we end up at 600 millimoles. Our unknown millimoles. So 600 times 1.25 to 750 millimoles. So we're going to want our 1.25. We have to weigh out to get 750 millimoles. So if we know back from 006 grams per mole. So 84.01 mole is equal to how many grams millimoles. Okay, so we need to convert this mole again, millimoles. So we've got 84.006 grams over 1 to how many grams over 750 millimoles. So 84.006 grams times 750 millimoles times 1,000 millimoles. So we've got our grams there. So we get rid of that and divide 750 by 1. Then we're going to get 84.006 grams. We're just going to get our...