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Topic: Calculating Specific Heat Capacity  (Read 2964 times)

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Offline ShadowSpirit

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Calculating Specific Heat Capacity
« on: April 21, 2007, 02:38:42 PM »
Sorry, I know this is more physics than chemistry, but I am stuck on this question and I hope someone can help me... (the numbers in {}'s are exponents as I don't know how to type those)

Question: A vessel of heat capacity 126 J/°C contains 0.2 kg of water and 0.02 kg of ice at 0 °C. What would happen if 0.1 kg of steam at 100 °C were passed into the vessel?

Given:
specific latent heat of ice is 3.34 x 10{5} J/kg
specific latent heat of steam is 2.268 x 10 {6} J/kg
specific heat capacity of water is 4200 J/kg/ °C


What I wrote (I assumed the question meant the vessel, water and ice were both at 0 °C, since it seems too complicated otherwise):

Let the final temperature of the mixture be T.

latent heat of steam released + heat loss of steam=heat gain of water + latent heat of ice absorbed + heat gain of ice + heat gain of vessel

2.268 x 10 {6} J/kg x 0.1 kg + 4200 x 0.1 x (100-T) = 4200 x 0.2 x (T-0) + 3.34 x 10{5} x 0.02 + 4200 x 0.02 x (T-0) + 126 x (T-0)

226800 + 42000 - 420T = 840T + 6680 + 84T +126T

262120 = 1470T

T= 178 °C


...Which doesn't makes sense at all. You can't mix something at 100°C and something at 0°C and get a mixture of 178°C... It'd be greatly appreciated if someone can tell me what went wrong with my calculations. Thanks.
« Last Edit: April 22, 2007, 04:11:52 AM by ShadowSpirit »

Offline Yggdrasil

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Re: Calculating Specific Heat Capacity
« Reply #1 on: April 21, 2007, 07:24:44 PM »
Calculate the heat needed to bring 0.2kg of water and 0.02kg of ice at 0oC to 100oC.  How does this compare with the heat released by the condensation of 0.1kg of steam at 100oC?   What does this tell you about what happens?

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