How to Calculate Gas Usage in Pressure Drop Situation?

In summary, the conversation discusses the problem of pressure dropping in a welder's tank of oxygen gas from 150atm to 120atm, and the question of how much gas will be used. The ideal gas law is mentioned as a potential solution, but the lack of information about the temperature before and after makes it difficult to apply. The idea of the tank not changing in volume is also brought up, but it is acknowledged that assuming a constant temperature may not be logical.
  • #1
prehisto
115
0

Homework Statement


Pressure drops in welders tank of oxygen gas from p1=150atm to p2=120atm .
How much of the gas will be used ?

Homework Equations



The Attempt at a Solution


In my mind the simplest way of looking at this problem is to consider the process isothermal.
But then the volume of the gas increases when pressure drops (Ideal gas law). This contradicts the question.

Since I do not know the temperatures before and after, I don't know what to do. I am looking for different view at this problem, some help?
 
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  • #2
If you want to treat the gas as an ideal gas then state the ideal gas law.
Looking at the law, which of the variables is constant and which variable? List them.
i.e. does the volume of the tank change?
 
  • #3
Volume of the gas does not change if the tank is not elastic (I think not in this question) since the gas will always fill the whole tank.
 
  • #4
Simon Bridge said:
If you want to treat the gas as an ideal gas then state the ideal gas law.
Looking at the law, which of the variables is constant and which variable? List them.
i.e. does the volume of the tank change?
Guneykan Ozgul said:
Volume of the gas does not change if the tank is not elastic (I think not in this question) since the gas will always fill the whole tank.

OK, I Think it is logical to assume that Volume of tank does not change. Now I can rethink my solution.
##P_1V=n_1RT_1## and ##P_2V=n_2RT_2##
## \frac {n_1RT_1} {P_1} = \frac {n_2RT_2} {P_2}##
## \frac {n_2} {n_1}=\frac {T_2P_1} {T_1P_2}##

But It seems that I need the temperature before and after, which i do not have. And to assume that T=const seems to be to only way, but it also seems not logical.
 
  • #5
prehisto said:
OK, I Think it is logical to assume that Volume of tank does not change. Now I can rethink my solution.
##P_1V=n_1RT_1## and ##P_2V=n_2RT_2##
## \frac {n_1RT_1} {P_1} = \frac {n_2RT_2} {P_2}##
## \frac {n_2} {n_1}=\frac {T_2P_1} {T_1P_2}##

But It seems that I need the temperature before and after, which i do not have. And to assume that T=const seems to be to only way, but it also seems not logical.
You're supposed to assume that the tank is not insulated, so that the final and initial temperatures are equal to room temperature.
 
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Likes prehisto and Simon Bridge

FAQ: How to Calculate Gas Usage in Pressure Drop Situation?

1. What causes pressure drops in a tank of gas?

Pressure drops in a tank of gas can be caused by a variety of factors, including changes in temperature, changes in volume, and leakage. These factors can lead to a decrease in the number of gas molecules in the tank, resulting in a decrease in pressure.

2. How does temperature affect pressure in a tank of gas?

According to the Ideal Gas Law, as temperature increases, the volume of gas molecules also increases, leading to a higher pressure. This means that as the temperature in the tank increases, the pressure will also increase. Conversely, as the temperature decreases, the pressure will also decrease.

3. Can pressure drops in a tank of gas be dangerous?

In certain situations, pressure drops in a tank of gas can be dangerous. If the pressure drops too low, the gas may not be able to perform its intended function, such as powering an engine or maintaining pressure in a gas line. In extreme cases, a sudden pressure drop can also cause the tank to implode or explode.

4. How can pressure drops be prevented in a tank of gas?

To prevent pressure drops in a tank of gas, it is important to regularly check for and address any leaks in the tank or its connections. Additionally, maintaining a stable temperature and avoiding sudden changes in volume can help prevent pressure drops.

5. What should I do if I notice a pressure drop in my gas tank?

If you notice a pressure drop in your gas tank, it is important to investigate the cause and address it promptly. This may involve checking for leaks, adjusting the temperature or volume, or seeking professional assistance. Ignoring a pressure drop can lead to safety hazards and affect the performance of the gas in the tank.

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