What is the correct approach for solving thermodynamics questions?

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Homework Help Overview

The discussion revolves around thermodynamics problems, specifically involving heat transfer and gas properties. Participants are exploring how to approach calculations related to calorimetry and the behavior of gases at equilibrium.

Discussion Character

  • Exploratory, Conceptual clarification, Problem interpretation, Assumption checking

Approaches and Questions Raised

  • Participants are attempting to set up equations for heat transfer in a calorimetry problem and are questioning the correct approach to find the mass of steam needed. There is also confusion regarding the molecular mass of gases and the conversion to SI units.

Discussion Status

Some participants have provided insights into the equations and concepts involved, such as the relationship between heat lost and gained. However, there is still uncertainty regarding the correct setup and assumptions, particularly about the temperature of steam and its implications in calculations.

Contextual Notes

Participants are discussing the need to convert units to SI for proper calculations, and there is a mention of the latent heat of steam, which may not have been fully understood by all. The temperature of steam is also a point of contention, with references to standard conditions.

Paymemoney
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Hi
The following questions i am having trouble solving and need some help:

Homework Statement


A 50.0g copper calorimeter contains 250g of water at 20.0 degrees C. How much steam must be condensed into water if the final temperature of the system is to reach 50.0 degrees C.

Homework Equations


Unsure about the rule to use.

The Attempt at a Solution



[tex]m_cu * m_cu + m_w * c_w = m_cu * c_cu ( T_f - T_i ) + m_w * c_w ( T_f - T_i )[/tex]

[tex]0.5 * 387 (30) + m_w (4186)(30)[/tex]

[tex]m_w = 4.9kg[/tex]

i know this is incorrect, what should be the right way to approach this question?

Homework Statement


A cylinder contains a mixture of helium and argon gas in equilibrium at 150 degrees C. What is the rms speed of each type of molecule?

Homework Equations


[tex]\frac{1}{3}NmV_(rms)[/tex]

The Attempt at a Solution



My only problem i am having is finding the molecular mass. i found some hints online about this but i don't understand.

One of the answer they got was:
Helium = 4.003 * 10^-3kg/mol.

The part i don't understand is where they got 10^-3?

P.S
 
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Paymemoney said:
Hi
The following questions i am having trouble solving and need some help:

Homework Statement


A 50.0g copper calorimeter contains 250g of water at 20.0 degrees C. How much steam must be condensed into water if the final temperature of the system is to reach 50.0 degrees C.

Homework Equations


Unsure about the rule to use.

The Attempt at a Solution



[tex]m_cu * m_cu + m_w * c_w = m_cu * c_cu ( T_f - T_i ) + m_w * c_w ( T_f - T_i )[/tex]

[tex]0.5 * 387 (30) + m_w (4186)(30)[/tex]

[tex]m_w = 4.9kg[/tex]

i know this is incorrect, what should be the right way to approach this question?P.S

Heat lost by steam = Heat gained by water.
msL + mwcw(Ts - Tf) = (mcuccu + mwcw)(Tf- Tw).
where L is the latent heat of the steam.
 
what is the Temperature of the steam??
 
10^-3 comes because you have to take everything in si units for example in your final equation if you take r in joule mass should be in kg.
 
Paymemoney said:
what is the Temperature of the steam??
100 degree C
 
so how did you know it was 100 degree C??
 
Paymemoney said:
so how did you know it was 100 degree C??
In the normal pressure, temperature of the steam is 100 C
When it condenses, the temperature of the water is 100 degree C.
Please go through the latent heat topic.