Calculating Heat for Temperature Changes in a Rigid Container | Thermodynamics

In summary: No, pressure is not constant. If you use the ideal gas law, there is no difference to the answers. If you use the actual heat capacities of H2 gas, however, the heat capacity increases with temperature. See http://www.engineeringtoolbox.com/hydrogen-d_976.html" for example.
  • #1
Shayna
13
0

Homework Statement


A rigid container holds 0.680 g of hydrogen gas. How much heat is needed to change the temperature of the gas
From 50 K to 100 K?
From 250 K to 300 K?
From 550 K to 600 K?
From 2250 K to 2300 K?

The Attempt at a Solution


I calculated the first one using delta E_th = (3/2)N*K_b*delta T
= (0.68g/2.0158g/mol)*6.02*10^23*1.38*10^-23*50K=210J

I don't understand why there should be a difference the questions, it seems to me all the temperature difference is 50K
 
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  • #2
Shayna said:

Homework Statement


A rigid container holds 0.680 g of hydrogen gas. How much heat is needed to change the temperature of the gas
From 50 K to 100 K?
From 250 K to 300 K?
From 550 K to 600 K?
From 2250 K to 2300 K?

The Attempt at a Solution


I calculated the first one using delta E_th = (3/2)N*K_b*delta T
= (0.68g/2.0158g/mol)*6.02*10^23*1.38*10^-23*50K=210J

I don't understand why there should be a difference the questions, it seems to me all the temperature difference is 50K
If you use the ideal gas law, there is no difference to the answers. If you use the actual heat capacities of H2 gas, however, the heat capacity increases with temperature. See http://www.engineeringtoolbox.com/hydrogen-d_976.html" [Broken] for example. (Use: [itex]Q = mC_v\Delta T[/itex]). If you are using the ideal gas law, you have to use a molar heat capacity for Cv = 5R/2 since H2 gas is diatomic.

AM
 
Last edited by a moderator:
  • #3
For example From 250 K to 300 K
I got the Cv from the form =14.55 therefore Cp=Cv+R=22.84
LaTeX Code: Q = mC_v\\Delta T =0.68*10^-3 kg * 22.84* 50K = 776.56 J
But that isn't right
 
  • #4
Shayna said:
For example From 250 K to 300 K
I got the Cv from the form =14.55 therefore Cp=Cv+R=22.84
LaTeX Code: Q = mC_v\\Delta T =0.68*10^-3 kg * 22.84* 50K = 776.56 J
But that isn't right
Why are you using Cp? If Q = mC_v\\Delta T and Cv = 14.55, why are you using a heat capacity of 22.84? Is pressure constant in this process?

AM
 

1. What is thermodynamics?

Thermodynamics is the branch of science that deals with the relationship between heat, energy, and work. It studies how energy is transferred and transformed in various systems, such as engines, refrigerators, and chemical reactions.

2. What are the laws of thermodynamics?

The laws of thermodynamics are fundamental principles that govern the behavior of energy and matter in the universe. They include the first law, which states that energy cannot be created or destroyed, only transferred or converted; the second law, which states that the total entropy of a closed system always increases; and the third law, which states that the entropy of a perfect crystal at absolute zero is zero.

3. How does thermodynamics relate to everyday life?

Thermodynamics has many practical applications in our daily lives. It helps us understand how engines work, how heat moves through our homes, and how refrigerators keep our food cold. It also plays a crucial role in fields such as chemistry, biology, and engineering.

4. What is the difference between heat and temperature in thermodynamics?

Heat and temperature are related but distinct concepts in thermodynamics. Heat is a form of energy that can be transferred from one system to another, while temperature is a measure of the average kinetic energy of the particles in a system. In other words, heat is energy in transit, while temperature is a measure of the energy in a system.

5. What are some real-world examples of thermodynamic processes?

Some common examples of thermodynamic processes include boiling water, melting ice, and burning fuel. Other examples include the operation of a car engine, the refrigeration cycle in a refrigerator, and the expansion of gas in a balloon. All of these processes involve the transfer or conversion of energy according to the laws of thermodynamics.

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