Questions tagged [gas-laws]
Physical and chemical laws describing the properties and behavior of gases. This tag currently applies to properties and laws concerning both ideal and real gases.
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Why would breathing pure oxygen be a bad idea?
My textbook mentions that SCUBA tanks often contain a mixture of oxygen and nitrogen along with a little helium which serves as a diluent.
Now as I remember it, divers take care not to surface too ...
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What volume does one mole of an ideal gas occupy?
This has been bugging me for a while now...
Obviously, to calculate the volume/space occupied by a mole of (an ideal) gas, you'll have to specify temperature ($T$) and pressure ($P$), find the gas ...
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Why can we still breathe in valleys? [duplicate]
Air is 1% argon. Argon is heavier than air.
Why doesn't the argon concentrate in low-lying areas, choking out life there?
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Why are equations of state for a non-ideal gas so elusive?
The ideal gas equation (daresay "law") is a fascinating combination of the work of dozens of scientists over a long period of time.
I encountered Van der Waals interpretation for non-ideal gases ...
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What is a rigorous definition of gas volume, and how is the Van der Waals equation derived?
I am confused about the justification for the corrections to the ideal gas law in the Van der Waals equation: $$p=\frac{nRT}{V-nb}-a\left(\frac{n}{V}\right)^2$$
I understand that the equation ...
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Why is the van der Waals coefficient b equal to four times the volume of the particle?
In the van der Waals equation of state
$$\left[p + a\left(\frac{n}{V}\right)^2\right](V-nb) = nRT$$
the coefficient $b$ is supposed to represent the volume occupied by the particles. Why then is it ...
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How could the ideal gas law be discovered from experiments on real gases?
The gas laws, namely Boyle's Law, Charles' Law, Avogadro's Law and Gay-Lussac's Law, are all experimental laws. Combining these laws, we get the ideal gas law $pV=nRT$. Also, "real life" gases do not ...
user44637
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When I heat up a balloon, does the air inside increase in pressure as well as volume?
When I heat up a balloon, does the air inside the balloon increase in pressure as well as volume? I thought pressure and volume were inversely proportional? Or does pressure and volume increase as ...
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What's the difference between perfect and ideal gas?
There are all kinds of different dinstinctions in the internet, and I'd like to see what you guys thought.
Actually, I've been asked if the heat capacity of an ideal gas es independent of temperature....
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Why don't heavy and light gases separate in the atmosphere?
Everyone must have heard that balloons are filled with helium, and the fact associated with it that helium gas is light and light gases always go upward.
There comes a question to mind: if the molar ...
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Why is the carbon dioxide we exhale transparent?
Why is carbon dioxide that comes from dry ice opaque and smoky while the carbon dioxide that we exhale transparent?
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PV=nRT approximation on other planets?
In Chemistry class yesterday, I learned that real gases with low atomic masses behave like an ideal gas at high temperatures and low pressure. Since on earth at sea level the pressure is close to $1\ \...
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How does composition of air affect vapor saturation limit?
Suppose we hold temperature, pressure, and gas composition (say, a standard atmosphere) constant. Then we know that if we allow the water content of the air to vary it can range between 0 and some ...
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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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What causes spray cans to get cooler when shaken?
I've been searching the web for this phenomenon and surprisingly I found only one post about it. And the reply to this question about canned air begins with words:
I don't know about the shaking ...
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Why do some gases have lower value of Z for a particular pressure?
In the above graph,the minima of the curve for methane is more than that of nitrogen. Also, for a given value of pressure, the value of $Z$ for methane is less than that of nitrogen. They seem to meet ...
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Reason for negative Joule Thomson coefficient of Helium and Hydrogen at NTP conditions
Recently, while reading my textbook I came to know that Helium, Hydrogen and Neon are the only gases which have negative Joule Thomson coefficient at NTP conditions, i.e heating effect is observed ...
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What is the carbon dioxide content of a soda can or bottle?
I sort of know how carbonated beverages are carbonated: a lot of $\ce{CO2}$ gets pushed into the liquid, and the container is sealed. There are at least two things I don't know. First, how much carbon ...
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Can the van der Waals coefficients be negative in the van der Waals equation for real gases?
A gas described by van der Waals equation has the pressure that is lower than the pressure exerted by the same gas behaving ideally. True or false?
My approach
$$P(\text{ideal}) = P(\text{real}) + P(...
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Relation between constant-pressure and constant-volume heat capacities: Cp - Cv = nR
For an ideal gas, we have
$$C_p - C_V = nR$$
where
$C_p$ is heat capacity at constant pressure,
$C_V$ is heat capacity at constant volume,
$n$ is amount of substance, and
$R=N_\mathrm A\cdot k_\...
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Why does gas not liquify at a temperature above the critical temperature no matter how much pressure is applied on it? Why? [duplicate]
My textbook says that critical temperature is the temperature above which a gas cannot be liquified no matter how much pressure we apply on it. But why? What is so special about this 'critical ...
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Vapor Pressure Paradox
This is quite an interesting situation I had thought of. Consider two beakers, each containing $\pu{180 g}$ of water. Also, suppose one of the two has $\pu{1.8 g}$ of glucose dissolved in it. Let's ...
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How does the "kreosan" Coca-Cola rocket work?
A YouTube channel called "kreosan" (made by Russian-speaking people who I believe live in Ukraine) posted a video showing rockets made from bottles of Coca-Cola.
Here's what I've figured out from the ...
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Perplexing claim in Chang and Overby's "General Chemistry"
I'm reading the chapter on gases in Chang and Overby's book "General Chemistry: The Essential Concepts" [1, p. 145], and the following passage is causing me some confusion:
The work of the ...
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Why is the pressure correction in the van der Waals equation proportional to (n/V)^2?
The van der Waals equation for real gases is stated as follows:
$$\left(P + \frac{an^2}{V^2}\right)(V - nb) = nRT$$
For the coefficient $b$, we can reason out that more the number of molecules, the ...
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Pressure vs volume plot for real gas and ideal gas
Background
Recently I have been studying about the states of matter and came to the topic of ideal gases and real gases, and the laws related to them. While studying it from my textbook, I saw the ...
user84548
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Comparing van der Waals constant for gases
How can I compare the van der Waals constant $a$ (the liquefication constant) for different compounds based on my knowledge of bonding in the compound? Let's pick the following sample set:
$$
\...
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Isothermal vs. adiabatic compression of gas in terms of required energy
I am working on an instruction manual of sorts to be used with an introductory course in thermodynamics. As an example of problem solving, I attempt to answer the following question:
If you have ...
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Variation of compressiblity factor with temperature
While I certainly understand the order of temperatures, I can't find a reason for the curves to intersect at one common point.
Why do the curves intersect at one point? or do they really intersect at ...
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Do 1 mole of both dioxygen gas and its atoms occupy 22.4 litres at STP?
The ideal gas law states:
One mole of an ideal gas will occupy a volume of $\pu{22.4 liters}$ at STP.
Does this mean that both
$\pu{1 mole}$ of $\ce{O}$ would occupy $\pu{22.4 L}$ (or if this ...
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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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Ideal Gas Equation Contradiction [duplicate]
You have a regular balloon, and you decide to heat it up. The gas particles inside the balloon will gain kinetic energy, and so, the gaseous particles will collide with the internal wall of the ...
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How did Joseph-Louis Proust know what gases weighed?
Proust's work led him to conclude that compounds always contain the same ratio, by weight, of their constituent elements. How did he know (or deduce?) what gases weighed?
Precise answers appreciated ...
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If something is not hydrophilic, is it necessarily hydrophobic?
Is it possible to create hydrophobic water?
Two species are phobic within some medium under some conditions when they don't here together (cohere if they're the same species; adhere otherwise).
To be ...
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What determines humidity limit / dew point of the air? - Why can air only hold a certain amount of water?
From Wikipedia:
The dew point is the temperature at which the water vapor in a sample of air at constant barometric pressure condenses into liquid water at the same rate at which it evaporates. At ...
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Is this equation of state original?
I created this equation of state as a personal undergraduate summer project (here is the link) seven years ago:
$$\frac{PV}{nRT}-1 \propto \left(\frac{nRT}{PV}\right)^2 \left[\left(\frac{nRT}{PV}\...
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Will CO2 bubbles ever fully dissolve in water?
Background:
Many aquarists keep freshwater planted tanks add $\ce{CO2}$ from a pressurized canister to their aquaria to promote plant growth. The injection is at a slow rate to get dissolved $\ce{CO2}$...
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Anomaly in van der Waals constants of noble gases
In van der Waals equation for a real gas, the equation is
$$\left(P + a\frac{n^2}{V^2}\right)(V - nb) = nRT$$
where $P$ is the pressure of the real gas, $n$ is the number of moles of the gas, $R$ is ...
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van der Waals coefficients for helium and neon
The values of the coefficient $b$ for helium and neon are
$$\begin{array}{cc}
\hline
\text{Element} & b\text{ / }\mathrm{dm^3\ mol^{-1}} \\
\hline
\ce{He} & 2.38 \times 10^{-2} \\
\ce{Ne} &...
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Why is dp/dv zero for a real gas in critical conditions?
I have read this fact in various websites but cannot understand the reason. What is an intuitive explanation of this?
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Best ways to compress and store tons of CO2? [closed]
We are looking at doing planet changing work, and removing CO2 from the atmosphere. The issue is storing the CO2. Please let us know the best ways to compress millions of tons of CO2, as we have ...
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Thermodynamic Derivation of Ideal Gas Law
The ideal gas law is perhaps the best-known equation of state, and admits both a derivation via the kinetic theory of gases and via statistical mechanics. But these are both microscopic theories, and ...
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Determine the molecular formula of the compound using percentage composition
I’ve attempted to solve this problem with percent composition, but it says the answer is wrong. Is it a $pV=nRT$ problem, and if so, can I use the units as they are given?
A $\pu{0.02867 g}$ sample ...
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In Graham's law, is the rate of effusion only dependent on molar mass?
According to Graham's Law, the effusion rate of a gas is inversely proportional to the square root of the molar mass of the gas.
However, consider this situation: We have s balloon with 1 mole of ...
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High pressure modification to the van der Waals equation
I get that a gas behaves non-ideally under high pressure and low temperature conditions. At high pressures, the density of a gas increases and attraction forces operate among molecules due to short ...
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Calculating Compressibility factor from the Van der Waals' Gas equation
So this problem has been bugging me for a long time. According to Wikipedia the compressibility factor $Z$ is defined as the ratio of the volume occupied by a real gas divided by the volume occupied ...
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How to calculate the pressure of an ideal gas that undergoes isothermal expansion?
A 2.35 mole sample of an ideal gas, for which $C_{\mathrm{m},v}=3R/2$ initially at $\pu{27 ^\circ C}$ and $\pu{1750 kPa}$, undergoes a two stage transformation. For each of the stages described in the ...
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Dubowski’s Formula vs Henry's law applied to alcohol sensor 'calibration'
I'm working with some hobby-level gas sensors and I've run across a "calibration" system I don't understand. A general description of this kind of gas sensor is described a bit more in this ...
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Arterial blood CO2 content, division and partial pressure
My lecturer cites Boron and Boulpaep's Medical Physiology (2nd edition) for the following claims:
the total $\ce{CO2}$ content of arterial blood is $26.4$ mmol/L or $48\%$ v/v (not sure if these ...
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Trying to understand the contradiction in the data of Proust/Dalton/Berzelius vs Gay-Lussac
I am trying to understand some of the historical context behind the discovery of atoms (pre-Avogadro). In particular, I am getting stuck in reading the following documents:
http://physics.unl.edu/~...
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