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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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 ...
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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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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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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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Why do helium balloons expand in volume as they go higher?
I realize as balloons go higher, the atmospheric pressure decreases, doing less to counteract the force of the gas particles pushing against the inner walls of the balloon. But at the same time, doesn'...
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Does exotic potassium exist?
I was reading a book called 'Hundred and Seven Stories of Chemistry'.
There is a chapter about how the attributes of different elements can change in presence of enormous pressure and temperature. ...
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In a perfect vacuum, shouldn't every solid be above its sublimation point, since its vapor pressure must exceed the atmospheric pressure?
If the sublimation point of a substance is the point where its equilibrium vapor pressure exceeds the pressure of the atmosphere upon it, and if every solid above absolute zero has some vapor pressure ...
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At what pressure will hydrogen start to liquefy at room temperature?
I want to increase a fixed-size object's internal gas pressure by generating hydrogen in it, but I could not find the proper phase diagram for it. So I am wondering how high pressures I can get.
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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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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 ...
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Pressure vs volume plot for real gas and ideal gas
Background
Recently I have been studying about the states of matter and came to the topic of ideal gases and real gases, and the laws related to them. While studying it from my textbook, I saw the ...
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In a liquid-in-glass thermometer, how does the gas pressure over the liquid affect the linearity of measurement?
In a common ethanol thermometer, the space above the alcohol column is filled with nitrogen. It also contains varying amounts of the alcohol in the gas phase.
Source: http://www.aashtoresource.org/...
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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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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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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 ...
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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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How does iceskating work?
I was willing to understand a little bit better the physics behind iceskating.
Messy thoughts
From New Scientist (1964) (probably not the most up-to-date reference $\ddot \smile$), I found a diagram ...
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Does high pressure reverse reaction between zinc and sulfuric acid?
When zinc is added to sulfuric acid, it undergoes a chemical reaction that generates hydrogen gas and zinc sulfate. Can this reaction be reversed by applying pressure to the products converting them ...
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What happened to this 10 year old unopened plastic bottle?
A colleague of mine found this unopened Aquarius bottle (non-carbonated drink) that was 10 years past its expiration date.
The bottle was collapsed inward which would suggest that the pressure in ...
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Bicycle tube inflation with 16g CO2 cartridge
How much pressure will a 16 gram cartridge of $\ce{CO2}$ (carbon dioxide) provide in a bicycle tire? Remembering my high school chemistry (forty years ago) and googling, I came up with this answer:
...
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When styrofoam shrinks from pressure, why doesn't it go back to normal after decreasing the pressure?
In this article (https://oceanexplorer.noaa.gov/explorations/16carolina/logs/sep3-2/sep3-2.html) and articles like this one, Styrofoam cups were taken to the depths of the ocean in an AUV to ...
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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 ...
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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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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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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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Are wrinkles\folds in paper reversible by heat, pressure or something else?
I ran into this question on Lifehacks.SE, regarding how to remove wrinkles from a crumpled piece of paper. Suggestions included ironing the paper or placing it under some heavy books for a few days.
...
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Decarboxylation of THCA during CO2 Extraction of Cannabis
We have a strange problem. We are performing CO2 extraction on cannabis and we are seeing considerable decarboxylation of THCA to THC.
We have high quality temperature sensors at the heat exchangers, ...
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Using Le Chatelier's Principle to Change Mechanical Energy to Chemical Energy
I was interested in an application of Le Chatelier's principle, where an increase in pressure could result in a decrease in the moles of gas.
In particular, a situation where when the pressure ...
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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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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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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 ...
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Calculate ozone layer thickness at a given temperature and pressure [closed]
The ozone concentration in the upper atmosphere averages $\pu{3.0 \times 10^13 molecules per cm3}$ in a region between $15$ and $\pu{35 km}$ high, at an average pressure of $\pu{0.001 atm}$ and ...
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Dealing with different units (psi) in ideal gas equation
My assignment is as follows:
A sample of air is trapped in a container at $\pu{16.2 psi}$. If the initial temperature is increased from $\pu{10 ^\circ C}$ to $\pu{32 ^\circ C}$, what is the final ...
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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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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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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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Does pressure affect pH? [closed]
Since pH is the function of $\ce{H+}$ ion concentration, the change in volume will change the equilibrium according to Le Chatelier's principle and affect the pH. Is it correct, or are there any ...
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Do gas particles colliding with each other affect the overall pressure?
Gas pressure is the pressure exerted by gas particles when they collide with the walls of the container. The gas pressure increases with the number of gas particles.
Does the collision between two gas ...
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Why does the vapour pressure not depend on the surface area and volume of a liquid?
My teacher said that vapour pressure is independent of the surface area and volume of a liquid. But I think it should be dependent, because surface area is directly proportional to the evaporation ...
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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 ...
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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) ...
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Calculating pressure inside a bag using the ideal gas laws
I was doing an experiment to inflate a bag using CO2 produced from a reaction between baking soda and vinegar. I came up with a balanced chemical equation and used the ideal gas law to calculate the ...
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Why do some reactions require specific pressures to happen?
For example, carbon monoxide reacts with hydrogen to synthesize methanol in the presence of some catalysts, but the pressure needs to be $\pu{50 atm}$ and the temperature needs to be $\pu{523 K}$.
...
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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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Henry's law and O2 concentration in alveoli blood
Can Henry's law be applied to find $\ce{[O2]}$ in alveoli blood? This kind of question appeared in an another forum and I've been struggling to find a definitive answer. My initial thought was 'no', ...
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How accurate would be the following conclusion on 'Critical Temperature'?
"Boiling does not occur when liquid is heated in a closed vessel. On heating continuously vapour pressure increases. At first a boundary is visible between the liquid and vapour phases because liquid ...
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Vapor pressure vs. ambient pressure
I've managed to get myself thoroughly confused in thinking about the vapor pressure of a substance at a particular temperature $T$, and how it relates to the pressure of the substance if it is in a ...
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Why do gases under low pressure conduct electricity?
In J. J. Thomson's cathode ray experiment, he used a discharge tube in order to make the gas inside conduct electricity.
Why do gases under low pressure conduct electricity?
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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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