Heat/fusion/vaporization question?

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Homework Help Overview

The problem involves calculating the mass of steam required to heat a given mass of ice from a sub-zero temperature to a specified final temperature of water. The context includes concepts of heat transfer, phase changes, and specific heat capacities.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the calculation of heat transfer involved in melting ice and condensing steam. Questions arise regarding the reasoning behind the calculated "remaining heat" and the values used in the equations.

Discussion Status

The discussion is ongoing, with participants examining the relationships between heat gained and lost during the phase changes. Some guidance has been offered regarding the equality of heat lost by steam and heat gained by ice, but no consensus has been reached on the calculations.

Contextual Notes

Participants are working with specific heat values and phase change energies, and there is mention of potential errors in the original calculations. The problem setup includes specific constraints related to the initial and final temperatures of the substances involved.

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Homework Statement


Given 150g of ice at -15oC, how much steam (at 100oC in g) is required to give a resultant of 50oC water?


Homework Equations


q=lm
q=cmT
heat for vap: 2256j
heat for fusion: 333J


The Attempt at a Solution


I got something like
remaining heat: 49950-2256m
change heat with remaining water: 4.19(150+m)T
and that m(100)/(150+m)=50 (error here?)

In the end, i got something like m=9g, which is too little, cause answers says 33g
 
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pirates01 said:
I got something like
remaining heat: 49950-2256m
What exactly is your reasoning for this "remaining heat"? What is 49950 and how did you get it?
 
remaining heat: 49950-2256m

I got this from q=lm
where 49950 is the joules taken to melt ice to liquid, and 2256m (where m is the mass of gas) is the joules given off to turn steam to liquid.
 
When you end up with water at 50 oC, you need to say that the heat lost by the steam is equal to the heat gained by the ice. In other words,

Heat to turn steam to liquid + Heat to reduce T of condensed steam from 100 oC to 50 oC

is equal to

Heat to turn ice to liquid + Heat to raise T of melted ice from 0 oC to 50 oC.
 

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