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Learn the toughest concepts covered in your GOB - General, Organic, and Biological Chemistry class with step-by-step video tutorials and practice problems.

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Osmolarity (ionic molarity) represents the number of moles of ions per liter of solution.

Osmolarity
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concept

## Osmolarity 1m
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Osma Larry T, sometimes referred to as Ionic Polarity, represents the number of moles off ions per leader of solutions. So sounds kind of familiar. We know that polarity represents moles of solute per leaders of solution. Now we're looking at salutes that have charges because now we're looking at ions and we're gonna say when it comes to Osmo clarity, there are a few different methods that we can employ to answer particular questions. Now, in Method One, we have direct calculation off osmo clarity. In this first method, we use the moles of ions and the leaders off solution with, um, it's formula to calculate Osma clarity. Now here this is just simply Osma Clarity equals moles of ions over leaders of solution again pretty similar to Mole Ari, which is just moles of solute over leaders of solution. Now that we've gotten the basic understanding of what Osma Clarity represents, let's click on to the next video when start doing some example questions dealing with Osma clarity under method one

Direct Calculation of Osmolarity: 2
example

## Osmolarity Example 1 2m
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in this example question, it says, calculate the molar ity of chloride ions when dissolving 58.1 g of aluminum chloride in enough water to make 500 MLS of solution. All right, even though they don't directly say it, they want you to calculate the molar ity of ions. So they want you to find Ionic polarity or Osma Larry E. Here polarity will equal the moles off chloride ions divided by leaders off solution. We already have the volume of our solution. We just have to change the 500 mL into leaders. So remember, one Millie is 10 to the negative three leaders, so that comes out 2.500 leaders. So now we have 0.500 leaders here on the bottom, and we have to find moles of chloride ions. So we're gonna take the 58.1 g of aluminum chloride, and we're gonna convert those grams of aluminum chloride in tow. Moles of aluminum chloride, One mole of aluminum chloride. What is the mass of it? Well, we look on the periodic table. It's composed of one aluminum and three chlorine. According to the periodic table, the atomic mass of aluminum is 26.98 g and that of chlorine is 35.45 g. Multiply these numbers and when we add them together we get 1 33. g. That represents the mass of aluminum chloride. So grams of aluminum Plowright cancel out. Then we're gonna convert moles of aluminum chloride. So one mole of aluminum chloride has within the Formula three. Clarence. So that would be three moles off chloride ions. So when we multiply everything on top, divide by what's on the bottom. We get 1.3073 moles of chloride ion, take those moles, plug him up Here Come. And then when we divide, we get 2.6 one mole aren t And that would be the morality of our chloride ions. Now, with our within our choices here, this has three sick fix here. This has only one Sig Figs. But here we're just gonna say 2.61 Mueller because just saying three Mueller I feel is too much of a rounding decision. So we're gonna say 2.61 is the molar ity of our chloride
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concept

## Osmolarity 37s
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The second method involves determining the Osma clarity from the polarity. Now we're going to say if the polarity of a compound is known, then the Osma polarity for each of its ions can be determined by Osmo. Polarity equals number off ions okay, that are within that compound times the molar ity of the compound overall. So this is yet another way that we can isolate Osma polarity. Now that we've seen the second method, click on to the next video. Let's take a look at a question where were asked to calculate the odds more clarity off a particular ill.

Osmolarity from Molarity of compound: 4
example

## Osmolarity Example 2 1m
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now remember method to we can use OSB Olara t equals number of ions times the polarity of the compound Here In this example, it says What is the concentration off hydroxide ions in a 0.350 Mueller solution off gallium hydroxide which has a formula of G a O. H. Three. All right, so we need to find the Osma clarity of hydroxide ions. So it's morality of O. H minus ions. It equals the number of hydroxide ions. If we take a look here at the formula, we see that there's a three here meaning that there are three hydroxide within this parentheses, so that would be three times now. The polarity of the original compound gallium hydroxide as a compound has a polarity up 0.350 Moeller. So now just do three times that value. And when we do that, we get 1.5 Moeller as the Osma polarity off hydroxide ions. So it's a simple is that if you know the polarity of the compound overall, use that to help you find the odd more clarity of any one of its ions.
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example

## Osmolarity Example 3 2m
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Method three involves the number of ions from polarity. Now we're going to say here problems involving number of ions and polarity can use a given amount and converting factors to isolate and end amount. Now, for those of you who haven't watched my videos on dimensional analysis and conversion factors, these terms basically formed the foundations for a lot of the calculations you'll see in chemistry. Your conversion factor is basically just when you have two different units connected together that is seen in polarity. Because morality itself represents moles per liter, two units connected together are given amount is just a value that's given to us. That has only one unit that would be represented by these leaders here and then Our end amount is just simply the value or the amount that we're trying to find at the end. Now, if we look at this question, remember, when we have the word off in between numbers, it means that we have to multiply them together. So we're going to say here are given amount. Where we're starting is 0.1 to 0 leaders, and we're gonna have to utilize conversion factors to get to our end amount our end amount we're looking for is moles of calcium ions. Now we need to cancel out leaders here. We're able to do that by utilizing the polarity given to us. The polarity is 0.450 Mueller, which means 0.450 moles of calcium phosphate per one, leader of solution. So that's our first conversion factor. Then leaders cancel out. Now we have to just change moles of calcium phosphate into moles of just calcium ion. So here, for every one mole of our entire compound, we can see that from the formula. There's a little three there, which means that I have three moles of calcium ions. So then, if we multiply everything out that's on top, I'll be left with 0.162 moles off calcium ion as my final answer.

Using Molarity of compounds and L of solutions, moles of ions can be calculated.

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Problem

Which of the following solutions will have the highest concentration of bromide ions?

7
Problem

How many milligrams of nitride ions are required to prepare 820 mL of 0.330 M Ba3N2 solution?

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Problem

How many bromide ions are present in 65.5 mL of 0.210 M GaBrsolution? 