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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3
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2answers
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 ...
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2answers
2k views

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?
3
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1answer
164 views

Control the pressure of Hydrogen in a small container without the use of a pressure regulator

I had recently asked this question, and due to the comments and general consensus of safety concerns, I decided to re-ask the question, attacking the problem from another angle. The Problem I need to ...
19
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1answer
507 views

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 ...
2
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1answer
852 views

Doubts on Diffusion/ Effusion of gases at different pressures

Let's start with a question: "One mole of nitrogen gas at 0.8 atm takes 38 s to diffuse through a pinhole, whereas one mole of an unknown compound of Xenon with fluorine at 1.6 atm takes 57 s to ...
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1answer
2k views

Is the pressure of a gas proportional with the concentration of a gas?

Is the pressure of a gas proportional with the concentration of a gas? Because you can also use the pressure instead of the concentration in the equilibrium condition.
2
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1answer
246 views

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 ...
2
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4answers
1k views

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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1answer
2k views

Vapor Pressure - Sealed Vessel

I have read that vapor pressure is only affected by temperature, but all of the examples have been in a sealed vessel. I have also read that pressure does not affect vapor pressure. I am looking for ...
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1answer
190 views

Pressure increase on rate of reaction

For reactions involving gases, an increase in pressure is no different from increasing the concentration of reactant particles, thus increasing the rate of reaction. But for reactions involves ...
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1answer
10k views

How to figure out which substance has the highest osmotic pressure? [closed]

In preparing for an exam and I'm trying to solve the following question. I'm clueless. What should I do? Which of the following water solutions has the highest osmotic pressure? \begin{align} \...
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1answer
882 views

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 ...
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4answers
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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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2answers
3k views

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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1answer
328 views

Non-Ideal Gas Behavior

I obtained measurements of temperature and pressure at various temperatures ($-10, 0, 20, \text{ and } 50^\circ \mathrm{C}$) and plotted them on a graph. Projecting backwards, the best-fit line ...
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0answers
2k views

What is the temperature at which lava evaporates?

According to this article -> http://ntrs.nasa.gov/search.jsp?R=19660041998 Lava evaporates under natural conditions, but apparently, only a little bit. I'd like to know the temperature at which ...
2
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1answer
825 views

Stability of CN molecule

The $\ce{CN}$ molecule has been observed spectroscopically in comets where pressure has been estimated to be as low as $10^{-10}\ \mathrm{mmHg}$. Draw a Lewis structure for $\ce{CN}$. Suggest an ...
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1answer
3k views

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 ...
4
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2answers
850 views

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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0answers
122 views

How to test acid-base reactions under pressure?

I am trying to test chemical reactions, more specifically reactions between an acid and a base, at different levels of pressure. I would like to know if there is some kind of equipment I can get that ...
3
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1answer
448 views

What is the pressure belonging to in Boyle's Law?

Just a hour ago, I was reading the great and highly interesting, Boyle's Law. In my textbook, there is given Boyle's Law and leaving some pages, there is stated Dalton's Law of Partial Pressure. ...
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2answers
20k views

How to calculate air tank capacity from tank displacement, tank fill (gauge) pressure, and specific type of gas?

I am trying to calculate the amount of a specific compressed gas that will fit in an air tank of specific displacement, at a specific pressure. This is in reference to compressed air guns. The inputs ...
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1answer
160 views

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 ...
2
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1answer
17k views

What is the relation between partial pressure and concentration?

So, one of my books said that partial pressure plays more significance in determining the gradient than concentration. So, it said it was possible for a gas to go from high partial pressure at point A ...
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4answers
2k views

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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3answers
230 views

When it is said 'at constant pressure, at constant pressure ', is it about pressure & temp. of the system or surroundings?

These are the following statements: [...] the thermal decomposition of $1.0$ mole $\ce {CaCO3}(\text{s})$ at $1$ bar results in an increase of volume of nearly $90~\text{dm}^3$ at $800^\circ \text{...
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1answer
176 views

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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0answers
2k views

Why does melting point depend on external pressure?

The melting point of a substance is the temperature at which the solid form's vapor pressure equals the liquid form's vapor pressure. I read that the vapor pressure of something depends ONLY on the ...
4
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2answers
8k views

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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2answers
2k views

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_{\...
3
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1answer
24k views

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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2answers
939 views

Calculate the partial pressure of NO2

Calculate the partial pressure of $\ce{NO2}$. $$p_{\ce{N2}}/p_{\ce{O2}}=5$$ $$\ce{N2(g) + O2(g) <=> 2NO(g)}$$ Let’s assume $K=0.1$ $$K= \frac{p_{\ce{NO}}^2}{p_{\ce{O2}}\cdot p_{\ce{N2}}}$$ $...
3
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2answers
113 views

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)}$...
2
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1answer
2k views

Pressure in Ideal Gas Law

In Boyle's law ($p$ inversely proportional to $V$ for constant $n$ and $T$), $p$ refers to the applied (external) pressure on the gas. However, in the ideal gas law, my textbook says that $p$ refers ...
0
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1answer
1k views

How high in (mmH2O) is the column of water in the tube?

A long glass tube, sealed at one end, has an inner diameter of 23.4 mm. The tube is filled with water and inverted into a pail of water. If the atmospheric pressure is 735 mmHg, how high (in mmH2O) is ...
3
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1answer
326 views

Calculating partial pressures from mixture of gases

A gas is enclosed in a container at $35~\mathrm{m^3\,mol^{-1}}$ and has the following composition at $49\,\mathrm{^\circ C}$ $\ce{N_2} \ 2\,\% $ $\ce{CH_4} \ 79 \,\%$ $\ce{C_2H_6} \ 19 \,\%$ Assuming ...
2
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2answers
2k views

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: $T_1$, $T_2$, $p_1$, $p_2$,...
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2answers
45k views

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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1answer
1k views

Osmotic Pressure

If the osmotic pressure of a 0.010 M aqueous solution of sucrose at 27˚C is 0.25 atmosphere, then the osmotic pressure of a 0.010 M aqueous solution of NaCl at 27˚C is (a) 0.062 atm (b) 0.12 atm (c)...
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0answers
134 views

Ice under very high pressure phase transitions [duplicate]

If you put a piece of ice into a very high pressure chamber and increase the pressure, I can understand how the ice turns to a water state. But what happens after that? Does the pressure push the ...
4
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1answer
2k views

Total pressure in a chamber calculation

I have a chamber containing two different gases and a liquid which needs to be heated at a certain temperature to bring it to vapor state. I have worked out that we can calculate the total pressure ...
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0answers
41 views

Addition of inert gas to equilibrium mixture under constant pressure [duplicate]

Adding inert gas under constant volume will not disturb equilibrium. But I want to know what would happen if inert gases are added at constant pressure. If total pressure remains constant and inert ...
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3answers
2k views

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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1answer
248 views

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 $$...
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3answers
990 views

Can you push a liquid and a gas into a container at different pressures?

I have a gas ($\ce{CO2}$ for example) and I want to infuse it into a liquid ($\ce{H2O}$ for example). I need a higher pressure of $\ce{CO2}$ to do this. So I push in water into a sealed container (at ...
3
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0answers
121 views

Could a vacuum airship be possible? [closed]

According to Wikipedia, a vacuum airship is a hypothetical airship that is evacuated instead of using a lighter gas. Really, once I first saw this, I thought, "Why did I never think about this before?!...
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4answers
16k views

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 ...
2
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1answer
33k views

Calculate the pressure of the gas samples as indicated by the manometer

Part A) Given a barometric pressure of $\pu{764.0 mmHg}$, calculate the pressure of gas sample (a) as indicated by the manometer. Part B) Given a barometric pressure of $\pu{764.0 mmHg}$, calculate ...
2
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1answer
2k views

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 $344.74\ \mathrm{kPa}$, ...
3
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1answer
45 views

Getting the pressure using the equation of states - will the answer be the same?

When I get the pressure using the different equations of state (e.g. van der Waals, Redlich-Kwong, etc.), will the answer still be the same?