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jvrxk posted an update 4 weeks ago

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jvrxk posted an update 4 weeks ago

4 weeks ago

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hey everybody in this video we're going to talk a little bit about solutions so solutions are very very common very very important for instance the bottle of dish soap on the left side of your screen that's an example of a solution and that picture of kool-aid that you see on the right side of your screen is also an example of a solution so let's review a little bit at this point I believe we should know what a solution is but it doesn't hurt to review so a solution is nothing more than a homogeneous mixture homogeneous means the composition the chemical composition of the mixture is the same throughout the entire mixture and in most applications solutions have two components which are called the solute and the solvent now the solute of a solution is the substance that gets dissolved so a solute is the smaller component it's the minority component of the solution the solvent is the majority component of the solution and it's the stuff that actually does the dissolving so in this diagram here and this is a diagram of a solution for instance and these little blue particles are dissolved in this purplish looking stuff now the purplish looking stuff that's what is doing the dissolving that's the majority component so that's what we would call the solvent and then these blue particles here that are dissolved in the purple stuff this is the minority component this is the substance that actually gets dissolved and we call that the solute now one of the most important and common types of solutions are called aqueous solutions now the term aqueous means that water is acting as your solvent so whatever solute you have if it's dissolved in water then you have what's considered an aqueous solution and the reason why a quiesce solutions are so important is because there's a lot of important reactions that take place in aqueous solutions and there's a lot of reactions in general that take place within aqueous solutions for instance the reactions that take place inside of lakes streams oceans are taking place within aqueous solutions and in addition a lot of the chemical reactions that place inside our bodies are doing so with an aqueous solution so the reactions that take place in every single cell of our body are actually doing so within an aqueous water-filled environment believe it or not our bodies are actually fifty-seven percent water by mass so what you're looking at when you're looking at me is mostly water believe it or not now let's talk a little bit about solution concentration and concentration refers to how much solute you have in your solution relative to the amount of solvent that you have if you have a dilute solution that means you have a very small amount of solute relative to the solvent in your solution and then if you have what's considered a concentrated solution that means you have a lot of salt a lot of solute relative to your solvent so for instance if I were to take just a pinch of kool-aid powder and dissolve it in a cup of water that would result in a very dilute solution dilute is just very watered-down not much solute in there at all and it probably wouldn't taste very good on the flip side if I have a concentrated solution that would be like taking five tablespoons of kool-aid powder & dissolving it in just one cup of water that would make a very potent very syrupy very concentrated solution of kool-aid now the terms dilute and concentrated are all fine and great but their relative terms we need a more absolute term by which to express the concentration of a solution now the most common term that is used to express solution concentration is called molarity and molarity is defined as the amount of solute that you have in your solution and that is in moles divided by the volume of the solution which is in liters so to get molarity which is represented by a capital M you just take the moles of your solute and divided by the liters of solution that will give you molarity so let's talk about how to prepare a solution of a specified molarity so let's say we're trying to prepare a solution that has one mole of sodium chloride dissolved in one liter of water this would be this solution would have a molarity of one we would call this a 1 molar sodium fluoride solution now the first thing that you would do is you would start adding your solute which in this case would be sodium chloride and you would start adding your solute to a volumetric flask so you would weigh out 1 mole of sodium chloride and you would add it to a volumetric flask in the next step you would add your solvent which is water so we would add that water until the 1 liter mark is reached so notice that we're not adding 1 mole of sodium chloride to a liter of water because remember to get the molarity the bottom of that term the denominator is not liters of solvent its liters of solution so if we added 1 mole of sodium chloride to one liter of water that would result in a total volume that is greater than one liter so instead we're adding the solute to the flask and then we are diluting it to the mark with solvent so then once we have added enough water to reach the 1 liter mark of this volumetric flask then we would shake the flask up mix the solute all in that solvent make sure it's thoroughly mixed and that would result in a solution that has a molarity of 1 we would call this a one point zero zero molar sodium chloride solution so in the next line I'm going to go over a simple calculation involving molarity and then we'll be all done so this problem says calculate the molarity of a 5.00 liter solution containing two point four seven moles of hydrochloric acid now remember the formula for molarity that's simply the moles of solute over the liters of solution so we're going to plug in those values we have two point four seven moles of our solute which is HCl divided by five point zero zero leaders of the HCL solution and that results in a molarity of zero point four nine four so this is a 0.49 four molar hydrochloric acid solution okay that's it for this video in the next video we'll talk a little bit more about solutions and calculations involving molarity and stuff like that so I hope this was helpful and alright that's it take care

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