Solve Thermo Probs: Part A of PV=mRT w/ Figure

• temaire
In summary, the conversation is about a problem involving the Ideal Gas Law and a figure given in the statement. The goal is to calculate the temperature using the given equation, but the pressure is needed first. It is determined that the pressure remains constant throughout state 1 and state 2 due to the constant atmospheric pressure and weight of the piston.
temaire

Homework Statement

[PLAIN]http://img821.imageshack.us/img821/8541/cheme.png

I am only looking for help in part a.

PV = mRT

The Attempt at a Solution

By looking at the figure, I was able to calculate the volume of state 2, which is half of the volume of state 1.

V1 = (mRT1)/P1
V1 = (5*0.287*573)/200
V1 = 4.11 meters cubed

V2 = V1/2
V2 = 2.06 meters cubed

However, in order to calculate the temperature by using the Ideal Gas Law, I need pressure first. How do I go about finding pressure? Is there an assumption I'm supposed to make first?

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How does the pressure arise initially? Can you connect a property of the piston to the pressure?

Mapes said:
How does the pressure arise initially? Can you connect a property of the piston to the pressure?

Well, I guess that since the piston does not exert a force on the air, the pressure stays the same throughout state 1 and 2?

Edit: Actually, the pressure arises from the weight of the piston and the atmospheric pressure. So since those two factors stay the same, the pressure is constant throughout states 1 and 2?

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The piston doesn't exert a force on the air? Or the piston exerts a constant force regardless of its height?

Mapes said:
The piston doesn't exert a force on the air? Or the piston exerts a constant force regardless of its height?

Yeah I edited my post, because I realized that since the atmospheric pressure and the weight of the piston are constant, the pressure doesn't change from state 1 to state 2. Thanks for the help.

1. What is the meaning of "PV=mRT" in thermodynamics?

In thermodynamics, "PV=mRT" is known as the Ideal Gas Law. It describes the relationship between pressure (P), volume (V), temperature (T), and the amount of substance (m) of an ideal gas. It states that the product of pressure and volume is directly proportional to the product of the amount of substance and the absolute temperature.

2. How do I solve thermo problems using the Ideal Gas Law?

To solve thermo problems using the Ideal Gas Law, you need to rearrange the equation to solve for the unknown variable. For example, if you are given pressure, volume, and temperature and need to find the amount of substance, you would rearrange the equation to solve for m: m=(PV)/(RT). Then, plug in the given values and solve for m.

3. What is the significance of the "R" constant in the Ideal Gas Law?

The "R" constant in the Ideal Gas Law is known as the Universal Gas Constant. It is a proportionality constant that relates the properties of an ideal gas to the amount of substance present. It has a value of 8.314 J/(mol·K) and is the same for all gases, regardless of their chemical properties.

4. How does the Ideal Gas Law apply to real gases?

The Ideal Gas Law is a simplified version of the more complex equations that describe the behavior of real gases. While it may not accurately describe the behavior of all gases, it is a good approximation for many gases at low pressures and high temperatures.

5. What is the role of the "m" variable in the Ideal Gas Law?

The "m" variable in the Ideal Gas Law represents the amount of substance, usually measured in moles. It is a measure of the number of particles present in a gas and is directly proportional to the pressure and volume of the gas. It is often used to compare the amounts of different gases in a given sample.

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