Types of Aqueous Solutions - Video Tutorials & Practice Problems
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When an ionic solid dissolves, ions leave the solid and become dispersed in the solvent. Three possible aqueous solutions can be formed:saturated, unsaturated and supersaturated.
Types of Aqueous Solutions
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Types of Aqueous Solutions Concept 1
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At this point, we know that solutions represent homogeneous mixtures, but what we need to realize is that there are different types of solutions that exist as well. Now we're going to say here that when solid solutes dissolve in a solvent, such as water, an equilibrium takes place. We're gonna say here we have what's called a solution equilibrium. This is when the rate of dissolution and recrystallization of solutes are equal. Now dissolution, we know that means that our solid solute breaks up into ions. Well, recrystallization will be the opposite of that. That's the process of where our dissolved solute starts reforming back into a solid. Now there are 3 possible aqueous solutions that are created. There's a saturated, an unsaturated, or a supersaturated solution. Now here, when we talk about equilibrium concentration, this is just the maximum amount of dissolved solute present in solution at a given temperature. So keep in mind, we have solutions which are homogeneous mixtures, and these solutions can either be saturated, unsaturated, or supersaturated.
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Types of Aqueous Solutions Concept 2
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Now here we're gonna talk about the different types of aqueous solutions. Now depending on the amount of solute added to our solvent, our solutions can either be saturated, unsaturated, or supersaturated. Now when we talk about the type of solution, we're going to say that our saturated solution is a stable solution, as well as our unsaturated solution. The super saturated solution itself though is unstable. Now the amount of dissolved solute in each, when we're talking about a saturated solution, that means we've reached our maximum amount of solute that's been dissolved. For unsaturated, we say we haven't reached our maximum amount of potentially dissolved solute. So that means additional solute can be dissolved. And then when it comes to our super saturated solution, we're gonna say super means greater than normal. So we've gone beyond our max. We've gone beyond our maximum amount of solute that can be dissolved. What effect does this have on our equilibrium concentration? Well, here, if you're a saturated solution, we've reached our maximum amount of dissolved solute, so we've reached an equilibrium concentration. Now here when you're unsaturated, you can further dissolve more solute because you haven't reached your equilibrium amount, so you're less than the equilibrium concentration. And then finally for supersaturated, we've gone beyond our max. So that means we're gonna have more than our equilibrium concentration. Now if we wanna think about this in terms of visually, in terms of solute being added, so let's say we have a 100 ml of water. This 100 ml of water can dissolve at max 20 grams of solute. So if I took those 20 grams of solute, all of them would be dissolved, and here our water has changed into this purple solution to show that it's a saturated solution. Now, again, we still have the 100 ml of water. Remember, it's maximum amount that it can dissolve is 20 grams of solute. Here, we're not dissolving 20 grams anymore, we're only dissolving 15 grams. So it's not as purple as our saturated solution because there's still room to dissolve an additional 5 grams of solute. And then finally, here we have our super saturated solution. Here, it can dissolve 20 grams max of solute, unless I do things to force it to dissolve an additional amount. Here, one of the things that we can do is increasing the temperature. By increasing the temperature, I can go beyond my 20 grams of solute, and in this case, I'm successfully able to dissolve 23 grams of solute. I have gone 3 grams over my maximum. I am beyond my max amount of solute dissolved. And you can see as a result of this, the solution is even more purple because it's gone beyond its equilibrium concentration. Right? So just remember, a saturated and unsaturated solution are both stable, they happen normally. A super saturated solution is not a stable solution, so it needs additional help. Adding heat is a good way of forcing a super saturated solution to be formed. Alright? So keep this in mind when comparing these 3 different types of solutions.
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Types of Aqueous Solutions Example 1
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Here, we're told that the solubility of a substance is 56 grams per 100 ml of water at 20 degrees Celsius. So, basically, we can dissolve up to 56 grams within 100 ml of water at that temperature. Now here we're saying a solution of this substance is prepared by dissolving 80 grams in a 100 ml of water at 75 degrees Celsius. The solution is then slowly cool cooled slowly at 20 degrees Celsius without any solid forming. The solution is alright. So we're at a higher temperature, so heat has been applied to it, allowing our solution to dissolve more than the 56 grams it normally can. Here it's dissolving 80 grams. They're telling us that we're cooling it back down at 20 degrees Celsius and nothing recrystallizes. That means we have still 80 grams dissolved as we cool down to 20 degrees Celsius. So we're still dissolving more than amount, our maximum equilibrium amount, and because of that, because we've gone beyond our max, we are a supersaturated solution. So here, we'd say, c is the correct answer. We've gone beyond our 56 grams that we normally would dissolve at 20 degrees Celsius. Of course, it makes sense that we go beyond that 56 degrees that 56 grams at a higher temperature. What's most important is when I get that down to 20 degrees Celsius, am I still dissolving that extra amount? If I am, then I'm a supersaturated solution. So here, option c will be the best answer. D doesn't work because let's take it back down to 20 degrees Celsius and see if any recrystallization has occurred. That's when we know for sure we have a supersaturated solution. Here, these answers don't work either.
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Problem
Problem
The solubility of KClO3 in water at 30ºC is 10 g per 100 mL of water. A 0.95 M solution of KClO3 in water at 30ºC is: