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Thermodynamics: Calorimeter problem

  • Thread starter petefic
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  • #1
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Homework Statement


A 50.0g copper calorimeter contains 250g of water at 20 deg celsius. How much steam must be condensed into the water if the final temperature of the system is to reach 50 deg celsius?


Homework Equations


Can someone explain how to find the Ls? I was told that just plugging in the latent heat of steam (2.26*10^6) is incorrect.


The Attempt at a Solution



Qsteam = Qcalorimeter + Qwater
ms * Ls = (mc * cc * dT) + (mw * cw * dT)
ms * Ls = (0.05kg * 0.0924cal/g * (50deg-20deg)) + (.25kg * 1cal/g *(50deg-20deg))
ms * Ls = 7638.6cal
 
Last edited:

Answers and Replies

  • #2
Andrew Mason
Science Advisor
Homework Helper
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Homework Statement


A 50.0g copper calorimeter contains 250g of water at 20 deg celsius. How much steam must be condensed into the water if the final temperature of the system is to reach 50 deg celsius?


Homework Equations


Can someone explain how to find the Ls? I was told that just plugging in the latent heat of steam (2.26*10^6) is incorrect.


The Attempt at a Solution



Qsteam = Qcalorimeter + Qwater
ms * Ls = (mc * cc * dT) + (mw * cw * dT)
ms * Ls = (0.05kg * 0.0924cal/g * (50deg-20deg)) + (.25kg * 1cal/g *(50deg-20deg))
ms * Ls = 7638.6cal
You have to assume that the steam is at 100°C.

You have the right idea in setting up an equation that equates the heat flow into the 250 g of water and 50 g calorimeter to the heat flow out of an unknown mass of steam. But the heat flow from the steam occurs in two stages: 1. the release of the latent heat of condensation and 2. the heat lost in reducing its temperature from 100C to 50C.

AM
 

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