Questions tagged [pressure]
For questions about gas pressure, or the effect of pressure in general on chemical species, substances, or reactions.
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Are diamonds really forever?
Common saying. Diamond possesses:
ultra hardness, (10 on the Mohs scale; 10000 HV on Vicker's Hard Test (iron merely 30-80))
hyper thermal conductivity, ($2320~\mathrm{W\, m^{-1}\, K^{-1}}$, or over ...
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What is the triple point pressure for Gallium?
I have seen various discussions about the triple point of Gallium determined to a very precise value, so precise that it is used as a reference for NIST scales and measurements.
However, these ...
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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 $7.45$ ...
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Room-conditions supercritical fluids?
Are there any reasonably obtainable supercritical fluids that I could, say, run my hand through? Wikipedia makes it sound like there are plenty of room-temperature ones, but no room-pressure fluids.
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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
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How does the partial pressure of gas C change with the change in volume of the container?
Suppose I have the equilibrium in a closed container:
$$\ce{3A(s) + 4B(g) -> 4C(g) + D(s)}$$
What happens to the partial pressure of C if the volume of the container is halved?
I was pondering ...
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Does the van der Waals equation remain valid when repulsive intermolecular forces dominate?
The van der Waals equation for a real gas is:
$$RT =\left(p+\frac{a}{V_\mathrm{m}^2}\right)(V_\mathrm{m}-b)$$
We have understood this formula by saying that $a$ is the term which is for force of ...
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Pressure exerted by a particle of ideal gas
There is a step I fail to grasp in the proof that for a monatomic ideal gas, $U=\frac{3}{2}PV$, where $U$ denotes the internal energy of the gas.
The proof involves considering a particle with mass $m$...
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When water boils at its boiling point how do we call it as an equilibrium?
On boiling, water becomes a vapor, liquid volume decreases and vapour volume increases. Since volumes are not constant, how do we call it as equilibrium?
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Can gaseous hydrogen and gaseous oxygen be compressed without reaction?
I'm looking into building a clean Bunsen-style burner (or rocket engine - I haven't decided yet). I will be using electrolysis to extract hydrogen and oxygen from water, but the apparatus I am ...
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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_{\...
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Osmotic Pressure definition clarification
currently reading Legninger's Principles of Biochemistry (8th edition if you absolutely needed to know) and under "Osmotic Pressure" it gives the definition to be:
Osmotic pressure, $\Pi$, [...
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Aside from carbon, what other substances can be made "superhard"?
So diamonds are an allotrope of carbon, that is formed when carbon is put under immense pressure, right? What other elements or compounds can you make into "diamonds", as in more durable, harder ...
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What is the difference between the units 'torr' and 'mm of Hg'?
According to present definition torr and mm of Hg differ though slightly.
I am still confused over it. Can someone write an explicit answer differentiating between them and the reason for ...
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What is "chemical pressure"?
While reading some publications on solid superconductors, I encountered a term "chemical pressure" a few times, which is usually attributed to the changes of superconducting transition ...
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Confusion in Van der Waals Equation
I understand that the behavior of ideal gases deviates largely from that of real gases in terms of pressure exerted by the gas molecules on the container in which it is present, space available for ...
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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 ...
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Will supercritical nitrogen stay supercritical if we raise temperature and pressure high above critical values?
Nitrogen's critical temperature is -146.96 °C and critical pressure 33.96 bar. If we maintain nitrogen at 220 bar and 400 °C, what will be the state of $\ce{N2}$? Will it be still supercritical? I ...
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Why does the cathode ray tube only start glowing at low pressures?
I am considering the cathode ray tube of the set up, when the cathode rays were discovered:
Voltage = very high
Gas = any
Atmospheric Pressure = changing
At different pressures, there are different ...
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Physical Explanation for variation of Gibbs Free Energy with Temperature and Pressure
Reading Atkins Elements of Physical Chemistry right now, and the book says:
"At constant pressure and entropy, an increase in temperature ($\Delta T\gt0$) results in a decrease in $G_\mathrm m$ (molar ...
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Gas Pressure and Molecular Mass
The ideal gas equation (or the van der Waals equation, for this matter) states that holding volume and temperature constant, increasing the number of moles of particles in the container will increase ...
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Does the rate constant depend on pressure?
I have read in some books that when pressure increases, the number of effective collisions increases. Hence, $k$ depends on pressure. Is it true? If so, then why doesn't $k$ depends on concentration? ...
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How much pressure does Gallium exert when it freezes?
Assuming the liquid Gallium is in a sealed container, how much pressure will it exert on its container when it freezes?
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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
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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 ...
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Is pressure equalization "diffusion"?
There is another question on the site which is:
Two containers, A and B, connected by a closed valve were evacuated and the Chlorine gas (Cl2) with a pressure of 200kPa was put into A and Oxygen (...
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Calculating the equilibrium constants for parallel reactions
So, I am attempting to calculate the equilibrium constant for two separate reactions.
$$\ce{A + B<=>C + D}$$
$$\ce{A + B <=> C + E}$$
I have figured out the final pressures at equilibrium ...
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Entropy as the driving force for osmosis
How is entropy responsible for osmosis and is movement of solvent possible from its higher concentration to lower concentration?
By concentration, I will be referring to the concentration of solvent ...
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Why is gas pressure measured in mmHg?
Pressure can be measured in $\pu{mmHg}$ which is equal to the pressure exerted by a “column of mercury” of a height expressed in $\pu{mm},$ at $\pu{0 °C}$ under Earth’s normal gravity.
Does the ...
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How do I calculate the pressure of a known liquid in a sealed container heated above boiling point?
If I have water in a sealed container heated to say 150 degrees, how do I determine the amount of pressure being generated in the container? What about for other liquids? I have searched extensively ...
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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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Can a liquid turn to a solid by applying pressure?
When pressure increases, volume decreases. If an extremely high pressure is applied to a liquid, is it possible to reduce it's volume to an extent where the molecules are very tight together, hence ...
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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
$$\ce{2 A(g) + 3 B(g) &...
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The effect of pressure on boiling point?
My textbook states the following:
Qualitatively, I understand why the boiling point of a substance increases when the pressure is increased. However, I learned that if the pressure is increased when ...
user33789
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Pressure dependency in Haber Bosch ammonia synthesis
Haber-Bosch ammonia synthesis reaction:
$$\ce{3H2 +N2 -> 2NH3}$$
According to the ideal gas law: $pV=nRT$ where constant volume implies $\displaystyle \frac nV=\frac p{RT}$
Then $\displaystyle ...
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Molecular kinetic interpretation of pressure
Regarding the molecular kinetic interpretation of pressure, we arrive at a point in the $F=\frac{\Delta P}{\Delta t}=\frac{2mvx}{\Delta t}$, that is to say, the force exerted in the shock on the wall ...
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