Two Fairly Basic Thermodynamics Questions

Click For Summary
SUMMARY

This discussion addresses two thermodynamics problems: calculating the mass of ice that must melt to gain 5 grams and determining the entropy change during an isothermal transformation of an ideal gas at 27.5°C. The relevant equation for the first problem is Q = Lm, where L represents the latent heat of fusion. For the second problem, the entropy change is calculated using the equation s(b) - s(a) = nR * ln(Vb/Va), with the work done by the gas being 3.5 J. The user struggles with applying these equations effectively to find the required variables.

PREREQUISITES
  • Understanding of latent heat of fusion in thermodynamics
  • Familiarity with the ideal gas law (pV = nRT)
  • Knowledge of entropy change calculations in thermodynamic processes
  • Basic algebra skills for manipulating equations
NEXT STEPS
  • Study the concept of latent heat and its applications in phase changes
  • Learn how to apply the ideal gas law in different thermodynamic scenarios
  • Explore entropy calculations for isothermal processes in detail
  • Practice solving problems involving work done by gases and related thermodynamic equations
USEFUL FOR

Students studying thermodynamics, particularly those tackling homework problems related to phase changes and ideal gas behavior.

jimmypoopins
Messages
64
Reaction score
0
Please help! I need these done by wednesday and for the life of me i cannot seem to get the correct answer.

Homework Statement


How much ice must melt at 0 deg. C to gain 5 g of mass?


Homework Equations


I cannot seem to find many equations that relate thermodynamics and mass, maybe that is my biggest problem... The only one i could find was
Q=Lm


The Attempt at a Solution


I know the latent heat of fusion, but i do not know Q. I tried dividing both sides by L, giving me Q/L=m, but i wasn't sure where to go from there.




Homework Statement


Calculate the entropy change in isotermal transformation of ideal gas at the temperature of 27.5 deg. C if work done by the gas is 3.5 J.


Homework Equations


s(b)-s(a)=Cv*ln(Tb/Ta)+nR*ln(Vb/Va)
pV=nRT
dW=pdV


The Attempt at a Solution


since Tb/Ta=1, Cv*ln(Tb/Ta) is reduced to zero, leaving us with
s(b)-s(a)=nR*ln(Vb/Va)
i then attempted to use the ideal gas law combined with dW=pdV but i found myself running in circles trying to figure out what to do with p and n and trying to find Vb and Va at the same time.
 
Physics news on Phys.org
anyone? please this is very important and it is due at 12:00 midnight. I've tried really hard and i will continue to try but if anyone can set me in the right direction i will greatly appreciate it
 

Similar threads

Replies
8
Views
2K
  • · Replies 2 ·
Replies
2
Views
3K
Replies
1
Views
1K
Replies
1
Views
1K
  • · Replies 10 ·
Replies
10
Views
3K
Replies
12
Views
3K
Replies
1
Views
2K
Replies
4
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 2 ·
Replies
2
Views
5K