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Ch.13 - Properties of Solutions

Chapter 13, Problem 78

What is the freezing point of an aqueous solution that boils at 105.0 °C?

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Hello everyone. Today we are being asked at what temperature does an equal solution boil? If it freezes at negative 5.5 degrees Celsius. And so the first thing we want to do is find a freezing point depression which is going to be the delta T. F. Is equal to the freezing boiling the freezing point of water which is zero degrees Celsius. We're gonna subtract that by the temperature that we have in the question stem which is negative 5.5 degrees Celsius. And when we do that we get 5.5 degrees Celsius. And so we take that temperature are freezing point depression. We take our 5.5 degrees associates and we are going to equal that to the freezing point elevation constant or K. F. Which is going to be 1.86 centimeters Celsius over Our M. We're going to multiply that by our end which is the morality of the solution. And so to rearrange the equation to find morality, we simply take that 5.5°C and we divided by that 1.86C over morality And we get a value of 2.957 M. And so next we have to find the boiling point elevation. And that's going to be T. B. Is equal to the More moral boiling point constant, which is 0.51 degrees Celsius over morality. We're going to multiply that by the morality that we found in our previous Calculation, that's going to be times 2.957 M. Our units are going to cancel out for our morality. And we're going to be left with a value Of boiling point elevation being equal to 1.52°C. And so now we want to find out what temperature does it boil. And so we take the boiling point of our water and that's going to be TB are boiling point is going to be equal to 100°C. The temperature that water boils at, plus the boiling point of elevation, which is 1.52°C. To get a final answer of 101.52°C. I hope this helped. And until next time.