Molarity

in these series of videos, we're gonna take a look at the concept of polarity, not morality. Itself is represented by the variable M and in class you'll hear more clarity and concentration, sometimes being used interchangeably. Remember, concentration represents the amount of given salute within a certain amount of solution. Now, mole Arat E is more specific. Molar ity represents the number of moles of solute per leader of solution. And with this we have our polarity formula similarity, which is capital m equals moles off salute over leaders off solution. Now that we have, um, or fleshed out idea of what concentration is due morality, let's take a look at some problems or ask the conflict polarity or to look at the components that help to make more clarity.

here, it says, to calculate the molar ity of a solution prepared by dissolving 23. g of sodium hydroxide in enough water to make 2. liters of solution. So here we're looking for more clarity. So mole arat E. Here equals are moles of solute, which would be the H. And it is. It's in a solution off 2.0 leaders, so we need leaders off solution. All right, we already have the 2.50 liters of solution, so we just need to convert the grams of sodium hydroxide into moles. So one mole of sodium hydroxide goes on the bottom, and then grams of sodium hydroxide goal. One more goes on the top and grams of sodium hydroxide go on the bottom. Sodium hydroxide is composed off one sodium, one oxygen and one hydrogen. Multiply them by their atomic masses from the periodic table, okay and then add up the totals. This will give us the Moller mask of sodium hydroxide, so we add that all up, it's 39.998 g, so that's going to go here. So here grams of sodium hydroxide cancel out and Now I'm gonna have moles of sodium hydroxide. So that comes out 2.59 to 5 moles. Take that and plug it in and we'll have the mole polarity of our solution. So this comes out 2. Moeller for solution.

Now that we know what polarity is, we can use it to help us calculate unknowns. We're gonna say problems with the polarity value present can use a given amount and conversion factors to isolate and end amount. Now, if you haven't watched our videos on dimensional analysis and conversion factors, I highly suggest you go back and take a look because it's just a continuation of this. We're now we're incorporating, incorporating more clarity into our calculations. Now the polarity value itself can represent one of those conversion factors. Because remember, conversion factors possess two different units connected together. Now, for example, we say 5.8 Moeller sodium chloride 5.8 Moeller represents 5.8 moles of N a. C L. Within one leader of solution. And because we're using two different units connected together, this is a conversion factor, so we can write it as 58 moles of N a. C. L. Over one leader of solution. So this is what 5.8 Moeller really represents. So keep that in mind when we start doing calculations that incorporate malaria

in this example question. It says how many grams of sodium phosphate, which has a molecular mass off 1 63.94 g per mole, are present in 300 mL of a 3000. Mueller sodium phosphate solution. All right, so in this question, they're asking us to discover grams. Now, before we start plugging in numbers and doing calculations, let's talk about what the sentence is saying and how we need to be on the lookout when we see it written in such a way. Now here we have a number, and here we have another number and they are connected together by the word off. Just remember, when off is in between, two values off is really telling us to multiply them together. Now we have more clarity here, which remember Mole Arat e equals moles over leaders and realize this that if I were to multiply both sides by leaders, then we would see that moles equals leaders times more clarity. Leaders times more clarity. Look at this. This is Miller leaders. If I were to convert those into leaders and then multiplied by the mole Arat E, that would give me moles of sodium phosphate. And we know if we have moles of a compound, we can use its molecular mass or Mueller wait to help us determine the grams of that compound. So that's the key. So just remember here when we have volume of polarity, that's really just telling us. Hey, you have moles there. All right, So we're gonna first take the 300 mL, and I'm going to convert it into leaders. Remember, this is a metric prefix conversion, so middle leaders go on the bottom leaders go on top. Remember that the metric prefix is on the same side with one. So one millie is 10 to the minus three milliliters. Cancel out. Now, I have leaders also remember that morality is a conversion factor. So that 0.550 Moeller is really saying that a half 0. moles off that compound over one leader. So I need leaders to cancel out. So I'll put the one leader here. And then we have 550 moles off sodium phosphate. Here leaders cancel out and look, I have moles of sodium phosphate. Finally, I convert those moles into Gramps, so one more of sodium phosphate. We're told that the molecular weight is 1 63. g. So plug that in so moles cancel out and I'll be left with grams at the end. So initially, what I'll get is 27.501 g of sodium phosphate. Looking at the question, 300.0 has 46 figs, 460.550 has three sig figs, and this number here has 56 things. We go with the least number of significant figures, So this comes out to be 27.1 g of sodium phosphate, so this would be the grams of our compound. So just remember, when they're giving us volume of morality, they're telling us what the moles are here. In this case, we just have to find grams. So take those molds that you've isolated and convert them into grams and you have your final answer