Calorimetry and Phase Changes

In summary, the problem involves finding the amount of steam that must condense inside a thermally insulated vessel, along with 2.40 kg of water and 0.450 kg of ice, in order to raise the temperature from 0.0 degrees Celsius to 28.0 degrees Celsius. The equation used is Qwater + Qice + Hv - Hf = 0, where Qwater and Qice represent the heat transfer from liquid water and ice, Hv is the heat of vaporization, and Hf is the heat of fusion. The correct answer according to the book is 190 g, but the speaker is still working on finding the solution.
  • #1
Aeonic333
12
0
My solution (179 g) to the problem below is slightly less than what the book says it should be (190 g)...

A vessel whose walls are thermally insulated contains 2.40 kg of water and 0.450 kg of ice, all at a temperature of 0.0 degrees Celsius. The outlet of a tube leading from a boiler in which water is boiling at atmospheric pressure is inserted into the water. How many grams of steam must condense inside the vessel (also at atmospheric pressure) to raise the temperature of the system to 28.0 degrees Celsius? Neglect the heat transferred to the container.

I set the problem up like this...

Qw + Qi + Hf + Hv = 0

Then I split Qw into two separate methods of heat transfer, since there is condensed steam changing from 100 degrees Celsius to 28.0 degrees Celsius, and liquid water change from 0.0 degrees Celsius to 28.0 degrees Celsius. This seems logical to me, but according to the book I am wrong. Any suggestions?

Tim
 
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  • #2
Hi Aeonic333,
in my naive understanding, the ice must melt before the temperature can rise. Did you take this into account?
 
  • #3
That is true. The ice must melt and the steam must condense, that is what Hf (heat of fusion) and Hv (heat of vaporization) stand for. I did make one mistake in my equation though: the heat of fusion needs to have a negative value since it is decreasing the overall energy of the system. So the new equation should be:

Qwater + Qice + Hv - Hf = 0

There still must be something I am neglecting, because I have yet to come up with the supposedly correct answer of 190 g for the mass of steam. I will be working on this until I figure it out, so please... SOMEBODY step up to the plate!
 

1. What is calorimetry and why is it important in science?

Calorimetry is the scientific measurement of heat transfer, specifically in chemical reactions or physical processes. It is important in science because it allows us to understand the energy changes that occur during these reactions and processes, which can provide valuable insights into the properties and behavior of substances.

2. How is calorimetry used to measure phase changes?

Calorimetry can be used to measure phase changes, such as melting or boiling, by monitoring the temperature changes that occur during these processes. As heat is added or removed from a substance, its temperature will change until it reaches the phase transition point. By analyzing the temperature data, we can determine the energy required for the phase change to occur.

3. What is the difference between specific heat and latent heat?

Specific heat is the amount of heat required to raise the temperature of a substance by one degree, while latent heat is the amount of heat required to change the phase of a substance without changing its temperature. In other words, specific heat measures the energy needed for a temperature change, while latent heat measures the energy needed for a phase change.

4. How can calorimetry be used to determine the energy content of food?

Calorimetry can be used to measure the energy content of food by burning a small sample of the food in a controlled environment and measuring the amount of heat produced. This heat can then be converted to calories or joules to determine the energy content of the food.

5. What are some potential sources of error in calorimetry experiments?

Some potential sources of error in calorimetry experiments include heat loss to the surroundings, incomplete combustion or phase changes, and equipment malfunctions. It is important to carefully control and monitor these variables to ensure accurate results.

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