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1
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1answer
27 views

How can internal energy be expressed as a function of any two of $p, v, T$?

In the book of Irey, Theormodynamics, the author states that (while talking about single phase substances) For a simple compressible media, we may choose our measurable independent variables any ...
0
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0answers
44 views

Thermodynamics, Phase change diagrammes

What would be the phenomena and PV, TV diagrammes for a closed vessel partially filled with water and subjected to heat, How change in vapour pressure would effect its boiling?, How PV, TV diagrammes ...
0
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2answers
44 views

Does the total energy in a volume (gas) increase linearly with increases in pressure?

If a volume has a certain pressure, then double that pressure at another time, is the total energy stored doubled? I'm sure this has to do with thermodynamics and if I remember correctly there is a ...
0
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2answers
32 views

What is the volume of liquid propane consumed when measuring gas flow at a given pressure?

We have a building with a large propane cylinder that distributes propane to different sources within the building. When the cylinder is filled, the propane is compressed to a liquid, and our bill is ...
3
votes
3answers
214 views

Why is there Net Work Done on a Pressure/Volume Cycle?

The area enclosed by the rectangle is said to be the Net Work Done. My question is why would there be any net workdone if it returns to its initial position (W). Shouldn't it act like a force-...
1
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2answers
51 views

What happens to pressure when a liquid turns into a gas in a confined chamber?

I'm doing an experiment requiring immense pressures. Since I do not have access to a pump that can create these pressures I settled on something different... Instead of using a pump I want to utilize ...
0
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1answer
28 views

Determining Gas Constant $R$ from Boyles Law?

I have done an experiment (Boyles Law experiment using Boyles Law Apparatus) in order to determine the value of the gas constant $R$. I have also taken into account the dead space volume in my ...
0
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1answer
52 views

What process is it when the polytropic index $n$ is equal to $- \infty$?

From $$Pv^n = \mathrm{constant}$$ When $n = - \infty$ What kind of process is it.... Eg... When $n= \infty$, It is constant volume.... Therefore when $n =- \infty$... What is constant?
0
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1answer
76 views

How to calculate the mass of gas needed to fill a cylinder to a certain pressure?

I m tasked with a tricky situation. I need to calculate the exact amount a tank can take in gas. But I dont know the volume of the tank. I just need to make sure that the tank reaches the right ...
0
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2answers
35 views

$p$-$V$ diagram and internal energy

I recently learned that if the initial state is equal to the final state in the $p$-$V$ diagram then the internal energy is equal to zero so that means $Q=W$. My question is how can you know that only ...
1
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3answers
131 views

What's the difference in a PV diagram that is curved versus one that is straight?

So what would the difference be between the graph above versus one that has the same inital and final points but the path is curved. I'm sure it has something to do with temperature, so does it mean ...
0
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0answers
27 views

Determining pressure as a function of time for water filled balloon

Looking to determine pressure as a function of time for a water filled "balloon" at extremely high pressures (~90MPa) with a fixed flow rate out. This is to determine the time it takes to hit a ...
0
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1answer
54 views

PV diagram of pure substance

Why does the specific volume of saturated solid state of water decreases with increasing pressure and the specific volume of saturated liquid wrt vaporisation increases with pressure? Can anyone ...
0
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1answer
64 views

Relationship between binding energy of atoms in a solid and compressibility defined by bulk modulus

Consider an atom which has η nearest neighbours. The equilibrium binding energy $L_0$ of $N$ atoms is: $$ L_0 = \frac{Nηϵ}{2} $$ The bulk modulus $K$ of a solid of volume $V$ compressed under pressure ...
1
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1answer
49 views

How to know heat flows out or in from a $pV$ diagram? [closed]

How to know heat flows out or in from $pV$ diagram?
1
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1answer
96 views

Difference between p-v and pressure and specific volume

what is the difference between pressure-volume and pressure-specific volume curves? since volume is an extensive property why do we plot pressure and volume curves for different processes?
1
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1answer
82 views

Can the volume fix the thermodynamic state of a system?

Can we use the volume to fix the thermodynamic state of a system? If not, why do we use P-V curves to know about thermodynamic states and processes?
0
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4answers
75 views

Does the pressure-volume-temperature realation of gases also work on solids?

I've read about the Combined gas law which said: The ratio between the pressure-volume product and the temperature of a system remains constant. My question is: Does this law also works on ...
1
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2answers
248 views

Virial expansion in terms of pressure

I'm studying thermodynamics and I found two forms for the virial expansion: $$pV~=~RT[1+\frac{A_2}{V}+\frac{A_3}{V^2}+\ldots] \tag{1}$$ and $$pV~=~RT[1+B_2p+B_3p^2+\ldots]\tag{2}$$ my problem is that ...
0
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1answer
478 views

Calculating work done by a gas fitted with a spring

Assume a gas in a container with one end closed and other end has a piston of mass m fixed with a spring.The gas is then heated ,assume that the container is non-conducting.(Assume vessel to be kept ...
0
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2answers
851 views

How is a helium tank volume measured?

I'm comparing different helium tank offers and I found an interesting one which seems to be what I want, but I'm unsure regarding the volume. It states: The content of gas of this tank is greater ...
1
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1answer
59 views

Do indicator/p-V diagrams only show reversible processes?

In Equilibrium Thermodynamics, Adkins, it is stated that Since equilibrium state corresponds to definite values of the system parameters, we may represent a quasistatic process by plotting...an ...
0
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1answer
432 views

Andrew's experiments on CO2

While studying andrew's experiment on CO2 i found a contradictory thing to my knowledge. At isothermal temperature 13.1°c as pressure increases volume decrease. At a particular pressure CO2 starts ...
0
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1answer
89 views

Why can the equation of adiabatic process $P_1 V_1^\gamma=P_2 V_2^\gamma$ be written as $\Delta P/P=-\gamma \Delta V/V$?

Why can the equation of adiabatic process $P_1 V_1^\gamma=P_2 V_2^\gamma$ be written as $$\frac{\Delta P}{P}=-\gamma \frac{\Delta V}{V},$$ where $P_2-\Delta P=P_1$ and $V_2+\Delta V=V_1$ as in ...
0
votes
1answer
112 views

Relation between surface area/shape and pressure

For a shape with a given volume and given gas pressure inside the volume, if the shape is changed to increase the surface area, will the internal gas pressure change?
2
votes
1answer
188 views

Deriving $Tds$ relations in thermodynamics

The Tds relations I refer to are, $$Tds = du + Pdv$$$$Tds = dh - vdP$$ The first equation is derived (assuming internally reversible process) from the definition of entropy $ds = \delta Q/T$ and the ...
0
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1answer
15k views

Hole in a water bottle

I understand that when you make a hole on a bottle filled with water and put the cap on tight the water will not flow out due to the atmospheric pressure acting on the hole. My confusion is that, lets ...
0
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2answers
70 views

Question about work done in $P$-$V$ diagram [closed]

$$A_1 = 0.5 (0.2) (1.5 \times 10^5) = 0.15 \times 10^ 5 \text{Pa m}^3$$ $$A_2 = 0.2 (1.0 \times 10^5) = 0.2 \times 10^5 \text{Pa m}^3$$ $$\frac{A_\text{total}}{\text{Work}} = 0.35 \times 10^5 ~\text{...
0
votes
1answer
570 views

Pressure-Volume Diagram

Why does pressure start off high in the Pressure-Volume Diagram starting from a compressed liquid to a super heated vapor? Noting that the temperature is constant in the process,I can't seem to ...
1
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1answer
120 views

Air breathing apparatus with pressure gauge and cylinder

I have got self contained air breathing apparatus with pressure gauge and cylinder. Cylinder has marking that it's 6 ltrs. When I open valve pressure gauge shows me 250 bars. Can I calculate the ...
3
votes
2answers
2k views

How to calculate the efficiency from a $p$-$v$ diagram?

Question: Calculate the efficiency of the real and ideal cycles. The process 1-2 is polytropic, 2-3 is isochoric, 3-4 is polytropic as well, and 4-1 completes the cycle with another isochoric process....
1
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1answer
604 views

How do scientists measure vapor pressure?

Experiment: We have a cylinder with a piston that is essentially weightless, frictionless, and exposed to atmospheric pressure. The cylinder has a volume of 2V, but half of it is filled with water and ...
0
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2answers
3k views

Deriving a thermodynamic relation using the Helmholtz free energy

I'm supposed to derive the following thermodynamic identity: $$ - \left( \frac{\partial U}{\partial V} \right)_{T,N} + T \left( \frac{\partial P}{\partial T} \right)_{V,N} = P $$ ...by starting with ...
0
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2answers
99 views

Novel ways to gauge pressure

I'm interested in determining the pressure of a pipe filled with compressed air with some degree of accuracy (~10% of total value~) using systems that are not just a supplied pressure gauge. eg - one ...
2
votes
2answers
172 views

When a soap bubble is blown inside another soap bubble why does the outer bubble not increase in size?

We blow one soap bubble with volume of air trapped ( say x) . We blow another bubble inside this bubble by blowing additional volume of air ( say y). So now the volume of air inside the first bubble ...
0
votes
1answer
364 views

V versus P in an Adiabatic Process

I have a question in which a gas undergoes a an expansion in such a way that the Pressure is a linear function of the volume on a V versus P diagram. One of the professors I asked said that means an ...
1
vote
0answers
32 views

Bends in piping [closed]

Plumbers made an error. Where there was one 90 degree elbow, there is now two 90 degree elbows within 1 ft of plumbing. I'm concerned about a loss of pressure or volume due to the extra elbow?
2
votes
3answers
75 views

Is there a prohibited region in $P-V$ plane?

Polytropic process generalize the particular thermodynamic processes with $$P V^{n}= \mathrm{constant}$$ Where, if $n$ changes, the curve on $P-V$ plane changes, as shown in the diagram. The orange ...
6
votes
1answer
105 views

How do pressured containers within pressured containers behave?

If a container could hold 60 PSI of pressure and was placed into a larger container with the same strength, could you fill the large container to 50 psi and the smaller one to 100 psi, creating only ...
2
votes
2answers
1k views

Pressure Volume graphs and work done

So if I have a system where pressure, volume, and temperature change, how do I find the work done on the system? I look at an example where you simply use $\mathrm{d}W =-p\, \mathrm{d}V$, but I ...
0
votes
1answer
132 views

Understanding the relation between pressure, ideal gas and, volume

I was given the following formula which is used for ideal gasses: $$pV = nRT$$ where: p:pressure V: volume n: number of moles R: gasconstant T: temperature now when speaking about vaporpressure ...
0
votes
1answer
58 views

Understanding why 2*density of a isolated gas equals half the initial temperature

A vertical cylinder of cross-sectional area 0.050 m2 is fitted with a tight-fitting, frictionless piston of mass 5.00 kg. The cylinder contains 3.00 mol of an ideal gas at 227°C. At what temperature ...
1
vote
1answer
2k views

Pressure Calculation - Compressed Air Volume [closed]

I am trying to calculate the change in pressure in a closed pressure vessel that is being compressed. For the sake of simplicity we can consider this to be a syringe with a closed end that is being ...
0
votes
1answer
404 views

why is air pressure in force per area instead of volume?

The basic unit of Pascals, (Pa), is one Newton (N) per meter square (area). Why is this, especially for things like air pressure that deal with three dimensional space? Shouldn't something like air ...
4
votes
3answers
2k views

Problem in understanding the Proof of $PV^{\gamma}$ =constant in thermodynamics

I have looked at the proof of this relation $PV^\gamma = C$; (where $P$ is pressure and $V$ is volume) in quite some places but I am not able to understand the logic behind the third step. In ...
1
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4answers
17k views

Specific heat capacity at constant volume VS constant pressure

For an ideal gas, why is the specific heat capacity at constant volume lower than the specific heat capacity at constant pressure?
1
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1answer
4k views

How do I keep the temperature constant in a Boyle's Law experiment?

I'm trying to get a head start on our lab experiment next week about Boyle's Law. The set-up is we have an air chamber can immersed in a pot of boiling water (which is kept boiling over an electric ...
4
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3answers
2k views

Would a person gain or lose weight after expelling a flatus?

Considering the chemical composition, mass, and pressure range of typical human flatulence, would a person gain or lose weight after passing gas?
0
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1answer
332 views

Question about pistons and how their volume is affected by particles?

I can't find an answer to this anywhere. When pressure is maintained in a piston and an ideal gas is injected into it (again, with no change in pressure as it is injected) the piston is displaced ...
2
votes
2answers
10k views

How does the bulk modulus of air change with rising pressure?

I can't seem to find the answer to what should be a trivial question: I have a rigid air-tight container of fixed volume and I am pumping air inside. The pressure is increasing (very slowly) from ~...