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What are the boiling point and freezing point of a 2.47 $m$ solution of naphthalene in benzene? (The boiling point and freezing point of benzene are $80.1^{\circ} \mathrm{C}$ and $5.5^{\circ} \mathrm{C},$ respectively.

Freezing point of solution=$$-7.14^{\circ} \mathrm{C}$$

Chemistry 102

Chapter 12

Physical Properties of Solutions

Solutions

Rice University

University of Maryland - University College

University of Kentucky

Lectures

03:58

In chemistry, a solution is a homogeneous mixture composed of two or more substances. The term "solution" is also used to refer to the resultant mixture. The solution is usually a fluid. The particles of a solute are dispersed or dissolved in the solvent. The resulting solution is also called the solvent. The solvent is the continuous phase.

05:06

In physics and thermodynamics, the natural tendency of a system to change its state is its tendency to increase the entropy of the system. It is a measure of the disorder in a system.

01:58

What are the boiling point…

02:54

The freezing point of benz…

01:41

Calculate the freezing poi…

01:39

What is the boiling point …

All right. So we want to compute the boiling point in the freezing point of a solution. Okay, To do that, we actually complete the variation. We have a formula for the variation, and then we compare that to dissolve and when it's pure. So we have the data for the solvent, which is being zing in this problem. So the first step will be calculating this delta tease how this temperatures, the boiling temperature and the boiling prison point is changing. So there are two formless I'm going to write in here. So the 1st 1 for the boiling point says the variation in the boiling point IHS equal it's gonna be equal this constant K b times the morality okay. And similarly for the freezing point who have a constant key f also times morality. However, for the freezing point, let's put a negative sign here. Okay, let's think why when you increase the concentration off particles in your solution the boiling point of your solution who go up right? So as this number heat increases, Delta T has to increase looking now for the freezing point, The more concentrated the solution is, the lower will be the freezing point. That's why we're putting this night of sign here too. No, Forget that fact. Okay, so we have the two forms here. You gotta look up those constant. I looked up and I found that for the boiling point. Elevation constant for benzene. It's too 0.53 and the units are degree. Celsius could be killed. Him to is the same. Um, per morality of the Pulau concentration. You could expend this into malls per kilograms, but I'm just gonna ride this way. Simplified. Okay. Same thing here. Uh, but the constant for the freezing point Depression, big benzene is five point 12 degrees Celsius. Horror, moral concentration. All right, so we have everything we need. Let's do the computation. So let's do first the boiling point. So we have delta t for boiling point of the benzene. We have the constant two point 53 degree Celsius for Malala concentration, and we have them allow concentration two point for seven. Great. Since a simple multiplication here, and you find that this variation will be 6.25 degrees Celsius. All right. And we know this is positive. So the boiling point off this solution will be the boiling point off the solvent. The pure solvent. Okay, which is given 80.1 houses and we add this change. Remember where we computed here in the top was the change. So we add this difference here, 6.24 and the final number will be 86 0.3 houses. Okay, Now we do pretty much the same for the freezing point. So the variation in the freezing point will be equal. The constant in this case is five 0.12 Sell shoes for Melo times, the Melo concentration that is given on the problem. Okay, this is no mass. Okay, I'm indicated this is moral concentration. And remember, this is negatives came. Therefore, the number that you compute here, which is 12.6 cells, is this is a negative variation. So whatever is your original number, it will go down by 12.6 degrees. Cells is so let's compute that the freezing point will be so for benzene. Normally, this prison point would be a 5.5 degrees cells is again. This is given on a problem. So from that, you're going to reduce 12.6 houses, okay? And you will find that you your temperature. You knew freezing point off. This solution will be minus 7.17

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