All Questions
Tagged with pressure thermodynamics
50 questions
5
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Relation between dilution and osmotic pressure
The following question is taken from IAT 2024, an entrance test for research institutes in India at the high school level:
Which one of the following plots correctly describes the variation of ...
- 159
3
votes
1
answer
120
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Effect of Pressure on the Position of Equilibrium
The following general reaction proceeds with decrease in amount of substance, so increasing pressure should shift the position of equilibrium to the right.
$$\ce{2 A(g) <=> B(g)}$$
But let's say ...
- 47
1
vote
0
answers
47
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How to treat enthalpy change and pressure in reactions involving a liquid and solid state
In physical chemistry, it is often stated that "at constant pressure, the change in enthalpy gives the amount of heat transferred into the system" and the justification for this claim is
$$...
- 31
6
votes
2
answers
851
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Heat capacity of (ideal) gases at constant pressure
I've come across this article which says that the constant pressure heat capacity is independent of pressure.
It also gives a mathematical explanation which says that any work of an ideal gas at ...
- 471
0
votes
1
answer
311
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Is fugacity the corrected pressure that should be used in thermodynamical models?
I am a little confused about fugacity and pressure of a gas. In ideal gases, pressure is same as fugacity. But for real gases this is not the case. Here is the link of the question that is the source ...
- 305
1
vote
1
answer
150
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Use the first law of thermodynamics to derive the pressure as a function of T, U, V and N
I am struggling with a thermodynamics question given
$$S(U,V,N)=C_VNK_\mathrm b\ln U/U_0+NK_\mathrm b\ln V/V_0$$ (where $U_0$ and $V_0$ are the reference energies and volumes) and the first law of ...
- 17
2
votes
0
answers
515
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How to calculate vapor pressure of ethanol at given temperature?
The following is a part of the problem I am struggling with. I think what I need is a vapor pressure of ethanol at $\pu{25 °C},$ but I may be totally wrong.
A reactor is charged with $\pu{60 bar}$ of ...
- 159
0
votes
1
answer
820
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What causes water to condense when air pressure is reduced?
In this video: https://youtu.be/IyBRGhXBuGw
The cabin pressure is reduced and subsequently a mist is formed.
What exactly is the cause?
-1
votes
1
answer
46
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What would happen if I increase the pressure and temperature of a gas present in a container
Assume the gas to be a real gas and the container to be made of diamond or anything stronger than that. Take the amount of gas to be 2mL and the pressure is increased with the help of strongest ...
- 11
2
votes
1
answer
344
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Does the vapor pressure of a substance depend on the presence of other gases?
The Clausius-Clapeyron equation (CC equation) can be used to find the (saturated) vapor pressure of a substance ie. the gas pressure at which the two phases (vapor + liquid or vapor + solid) reach ...
- 29
3
votes
2
answers
362
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Why does van der Waals' equation of state give only one P, V pair for a particular temperature here?
I came across this question which I initially ignored believing that the data was insufficient:
Calculate the pressure exerted by one mole of $\ce{CO2}$ gas at $\pu{273 K}$ if the van der Waals' ...
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0
votes
1
answer
171
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Effect of addition of inert gas on concentration in an equilibrium [duplicate]
We have the following equilibrium established in a container with movable piston at atmospheric pressure.
$$\ce{N_2 (g) + 3 H2 (g) ⇌ 2NH_3 (g)}$$
Now how does the concentration of the reacting species ...
- 11
2
votes
1
answer
176
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When does a piston stop in an irreversible process?
Suppose we have an ideal gas filled inside a container fitted with a piston. The external pressure is equal to internal pressure.
If we suddenly decrease the external pressure, we say that the gas ...
- 29
2
votes
1
answer
544
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Is it possible to store moist air at high pressure?
Is there any way to store moist air inside a high pressure tank?
Let's suppose that I have humid air (30%) at room temperature and I want to store it at 300Bar in a tank. when I extract the fluid from ...
- 131
2
votes
1
answer
84
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Finding equilibrium constant for the reaction between non-stoichiometric mix of gaseous components
$$\ce{CH3OH(g) + NOCl(g) <=> CH3ONO(g) + HCl(g)}$$
The volume of the container is $\pu{433 cm^3},$ $T = \pu{50 °C}.$ Methanol was added until the pressure was $\pu{50.1 mbar},$ then $\pu{0.059 g}...
- 1,095
1
vote
1
answer
242
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Work done by system of ideal gas in isobaric expansion
Consider a system of ideal gas in a container with piston and the isobaric expansion of gas takes place.
As the process is isobaric, so initially the pressure of gas is equal to atmospheric pressure ...
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4
votes
3
answers
269
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Work done on a Gas?
I'm extremely confused about work done on a gas. So if you look at the system pictured,
From what I've read online, the net work done, which is equal to the work done by the objects, is equal to the ...
- 69
3
votes
2
answers
296
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Effect on mass when decreasing pressure in equilibrium reaction
For example, if we have the reaction:
$$\ce{A + B <=> C}$$
And the volume is decreased, the pressure would increase. Hence, according to Le chatelier's principle, the system will partially ...
- 87
-1
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3
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827
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Can work be done on a body when temperature and pressure are changed without changing its volume?
Can work be done on a gaseous system when temperature and pressure are changed without changing it's volume?
In chemistry the formula of work is always $p\,\mathrm dV,$ whereas we can also do work on ...
-1
votes
1
answer
145
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Latent Heat, Vapor pressure and Equilibrium [duplicate]
So after reading about this topic i wanted to share what i learned and i wanted you guys to tell me if what i am writting is correct:
A pressure vessel has propane inside and it is pressurized. The ...
- 21
1
vote
1
answer
2k
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Clausius–Clapeyron equation: shape of phase diagrams makes no sense
I am trying to model the melting point of a substance at varying pressures (ranging from very small to very very large). All I am trying to do is make an equation that relates melting temperature to ...
2
votes
1
answer
239
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What actually happens to the volume of a gas in an isolated system?
In an isolated system with adiabatic walls in which gas is filled what exactly happens? How do we define the volume of a gas here? Is volume of 1 mole of gas present in that inelastic container the ...
-2
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2
answers
700
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How do you manage to liquefy a gas by applying only pressure? [closed]
How can you liquefy a gas by applying only pressure? To increase the pressure of a gas you need a compressor, and when the compressor does work on the gas , it will increase his pressure but at the ...
- 21
4
votes
2
answers
727
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Regarding units of water potential and chemical potential
If water potential is nothing but the chemical potential of a given solution, then why do their units differ?
If the unit for the latter is taken as 'Energy per molecule' (which makes sense to me ...
- 49
3
votes
1
answer
637
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Isothermal vs adiabatic compression of an ideal gas [closed]
Could someone please explain these specific questions physically (especially the first question!)? I understand the corresponding mathematical proofs, but not the physical reasoning? I have looked ...
- 33
1
vote
2
answers
604
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Which pressure is used for calculation of standard enthalpy change of the reaction with two or more gases?
Standard state conditions for standard Gibbs free energy change stipulate (among other conditions) that the partial pressure of each gas is $\pu{1 bar},$ e.g. for the reaction
$$\ce{2 A(g) + 3 B(g) &...
1
vote
2
answers
126
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How to derive this temperature-pressure-specific volume relationship?
(for isentropic, adiabatic, ideal gas flow)
$$\frac{T_x}{T_y} = \left(\frac{p_x}{p_y}\right)^{\frac{(\gamma-1)}{\gamma}} = \left(\frac{V_y}{V_x}\right)^{\gamma-1}$$ where $V$ is the specific volume, $...
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0
votes
2
answers
330
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Coffee cup lids
So this morning I purchased a coffee. As a not uncommon event the lid on the coffee cup didn't have a hole completely punched through (a gas inflow hole). This makes it difficult to drink the coffee ...
- 29
9
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4
answers
1k
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Is it true that an evaporating molecule has the same kinetic energy as a molecule in a pot of boiling water?
A molecule on the surface of room-temperature water shoots off the surface of said water, or in other words, it "evaporates." It does so because it gained kinetic energy ${x}$, and ${x}$ was great ...
- 201
2
votes
0
answers
95
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How do the pressure acting on the reactants and the initial temperature of the reactants affect the enthalpy of reaction?
In an exothermic reaction that occurs under constant pressure, does the pressure acting on the reactants affect the enthalpy of reaction? Does the initial temperature of the reactants affect the ...
- 341
6
votes
1
answer
22k
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Entropy and specific heat capacity
I have seen the equation $S(T_2)=S(T_1)+C_p\ln(T_2/T_1)$ where $C_p$ is the molar heat capacity at a constant pressure. I understand that this assumes that the temperature range is sufficiently small ...
- 1,717
-4
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2
answers
13k
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How does equilibrium change when pressure is increased? [closed]
What happens to the equilibrium when an increase in pressure is applied to a system with the same number of moles of gas on both sides of the reaction, according to Le Chatelier's Principle?
For ...
- 1
12
votes
4
answers
14k
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Why do we use the external pressure to calculate the work done by gas
I read in a textbook that in the case when we have a gas in a cylinder fitted with a massless frictionless piston being held with an external pressure $p_1$, and when the pressure is reduced to become ...
user38257
2
votes
1
answer
159
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Determining the amount of water to create a given pressure in a sealed container
I have a sealed container with a volume of 1 liter. I want to go from an initial pressure of $P_{1}=1\ \mathrm{atm}$ and an initial temperature of $T_{1}=298\ \mathrm{K}$ to a final pressure of $P_{2}=...
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3
votes
1
answer
11k
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How to find the molar mass of a compound given mass, vol, temp, and pressure?
A $2.1\ \mathrm g$ sample of a liquid vaporizes and exerts $120\ \mathrm{mmHg}$ pressure at $1.5\ \mathrm L$ volume and $80\ \mathrm{^\circ C}$ temperature. Find the molar mass of the gas.
I first ...
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3
votes
4
answers
2k
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Enthalpy of a reaction changes with temperature, does this mean bond strengths change with temperature?
During chemical reactions, the bonds between atoms break or form to either absorb or release energy. The result is a change to the potential energy of the system. The heat absorbed or released from a ...
3
votes
2
answers
5k
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Van der Waals real gas equation
Van der Waals corrected the ideal gas equation for real gases and gave the following equation:
$$\left(p+\frac{an²}{V^2}\right)\left(V-nb\right)=nRT$$
I’m very confused about one aspect of this ...
user33789
3
votes
2
answers
5k
views
Work done on a container, resulting in pressure change
Why does pumping gas into a rigid container (causing the pressure and temperature to increase), not mean that work has been done on the container?
Work is given by the formula : W = -P ΔV
If I go ...
- 2,851
19
votes
1
answer
555
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How to treat pressure in computational chemistry?
I have a reaction where a gas at high pressure and a solution with all kinds of species is involved. How do I take pressure correctly into account to get reasonable values for $G$?
Do I calculate ...
- 1,459
3
votes
1
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290
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Thermodynamics : Work Done by a Gas
Suppose in a piston in which there is a gas, the gas exerts pressure P on surroundings, whereas the surrounding exerts a pressure $P[ext]$ on the gas.
In order for the gas to expand, P must be ...
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1
vote
1
answer
1k
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Partial Pressure and Partial Molar Volume
When we define partial pressure and partial molar volume of a gas in a mixture, suppose $P$ is partial pressure of a gas in a mixture and $V$ is partial molar volume
then why the following equation ...
- 329
1
vote
1
answer
182
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When fugacity and z-compressability equations instead of Gibbs free energy equations?
In very high pressure environments such as mud circulating systems, conditions for polymers contain fugacity/z-compressability criteria instead of Gibbs free energy, more in the answer. So
When ...
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4
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2
answers
2k
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Does enthalpy equal heat when PV work is done?
The derivation that enthalpy equals heat at constant pressure goes like:
$$\begin{align}
H &= U + P_{\mathrm{int}}V \\
\Delta H &= \Delta U + \Delta (P_{\mathrm{int}}V)
\end{align}$$
If $P_{\...
- 2,052
3
votes
1
answer
30k
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Convert from Pa to Pa to J/dm^3 [closed]
Given the value 380 PaK^-1, how do I convert Pa to Jdm-3?
I know that 1 joule = 1 Nm, and that 1 pascal = 1 N/m^2.
But where does the dm^-3 (or L) come into this? I don't know where to start.
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5
votes
4
answers
467
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Will the total equilibrium pressure increase in gas phase reaction PCl5(g) ⇌ PCl3(g) + Cl2(g) after chlorine is removed?
Will the total pressure be greater than the initial equilibrium pressure if all $\ce{Cl2}$ is removed and the following reaction is allowed to re-equilibrate?
$$\ce{PCl5(g) <=> PCl3(g) + Cl2(g)}$...
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2
votes
2
answers
2k
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How to find the change in internal energy (q+w) for an expanding monoatomc ideal gas?
If a monoatomic ideal gas simultaneously expands against a constant external pressure and drops in temperature, how do you find the internal energy change?
Known values are: $T_1$, $T_2$, $p_1$, $p_2$,...
- 41
6
votes
1
answer
54k
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Reversible and Irreversible adiabatic expansion
A $\mathrm{200.0\ m^3}$ balloon at $253.0\ \mathrm K$ ascends to a higher altitude. If the initial pressure inside the balloon is $325$ millibar, and it ascends to a latitude with a pressure of $7.45$ ...
- 161
4
votes
3
answers
3k
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Work Done Upon Molecules
In which of the following processes is energy transferred into the substance by work ($w > 0$)?
a) Expansion of a gas against the surroundings
b) Expansion of a gas into a vacuum
c) ...
- 1,143
1
vote
1
answer
377
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What are analytical expressions for the isothermal change of Gibbs energy?
The change of Gibbs energy at constant temperature and species numbers, $\Delta G$, is given by an integral $\int_{p_1}^{p_2}V\,{\mathrm d}p$. For the ideal gas law, $p\,V=n\,RT$, this comes down to
$$...
- 1,012
2
votes
1
answer
4k
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Unknown Mass in Dalton's Law of Partial Pressures
An air with mass of $0.454\ \mathrm{kg}$ and an unknown mass of $\ce{CO2}$ occupy an 85 liters tank at $2068.44\ \mathrm{kPa}$. If the partial pressure of the $\ce{CO2}$ is $344.74\ \mathrm{kPa}$, ...
- 161