Latent Heat + Specific Heat Problem

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Homework Help Overview

The problem involves the thermal interaction between molten lead and water, specifically focusing on the amount of water that boils and vaporizes when the lead is introduced. The subject area includes concepts of latent heat and specific heat in thermodynamics.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to set up an energy balance equation involving latent heat and specific heat to find the mass of water that boils. Some participants question the numerical results obtained from the calculations, indicating discrepancies in their answers.

Discussion Status

The discussion is ongoing, with participants comparing their numerical results and seeking clarification on the calculations. There is no explicit consensus on the correct answer, but there is engagement in verifying the setup and numerical evaluation of the problem.

Contextual Notes

Participants are working under the assumption that no water evaporates until it reaches the boiling point, which is a critical aspect of the problem setup. The original poster has provided specific constants and equations relevant to the problem.

yaylee
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Homework Statement



Suppose molten (liquid) lead, mass ml = 9.83 kg, is at its melting point. The lead is poured into water of mass mw = 585 g and initial temperature Tw = 16.2 C. Find mwb, the amount of the water that boils.
NOTE: Reaching the boiling point is not enough; the question asks for the amount of water that vaporizes as well.
ASSUME: no water evaporates; it only vaporizes at the boiling point.

Homework Equations


Constants: M.P Lead = 327 C, MP Water = 100 C
Latent Heat Lead = 33 kJ/kg
Latent Heat Q = mL
Specific Heat Eq'n: Q=mcΔT

The Attempt at a Solution


mL + mcΔT = mcΔT + mL
9.83 kg (33 kJ/kg) + 9.83 kg(0.130 kJ/kg)(327C - 100C) = 0.585(4.186)(100 -16.2) + m(2260 kJ/kg)
Solving for m, we get m = 0.215 kg.

Did I go wrong in my reasoning here? Many thanks in advance for your help!
 
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Your equation looks good to me. But I don't get the same numerical answer.
 
TSny said:
Your equation looks good to me. But I don't get the same numerical answer.

What do you get when you plug and chug in the values? I worked on the similar type of problem, and I got stuck on it from using that equation.
 
I get about 0.181 kg. What do you get for the numerical value of the left side of the equation? What do you get for the simplified form of the right side?
 

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