All Questions
Tagged with van-der-waals-behavior physical-chemistry
18 questions
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Why is Inversion Temperature not equal to Boyle's temperature?(Theoretically)
Mathematically, it is proven that the inversion temperature is twice that of Boyle's temperature.
But if a gas is not showing the Joule-Thompson effect, it is behaving ideally and it has no ...
- 136
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2
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141
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Can we calculate van der Waals' constant a for the following case?
The given Z vs P curve for 1 mole of a gas at 400K starts at Z=1 & P=0.
The slope at the point when the curve again intersect Z=1 is 0.005. The critical temperature of the gas is 500K.
My approach:...
- 208
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845
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Why is real volume not smaller than ideal volume in the van der Waals gas equation correction terms? [duplicate]
The following equation is valid for ideal gases
$$pV=nRT$$
Please mind the following notation, any parameter that is related to an ideal gas would be denoted with a subscript $i$ and anything related ...
- 17
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Why is the excluded volume in van der Waals 4 times the actual volume of the gas molecule?
I am having trouble understanding why the excluded volume of a particle is four times its actual volume.
According to Wikipedia,
"The excluded volume b is not just equal to the volume occupied by ...
- 342
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How should I evaluate $\left(\frac{\partial U}{\partial V}\right)_T$ with van der waals equation: $P = \frac{nRT}{V-nb}-a(\frac{n}{V})^2$?
So in my homework I was able to get this-
$\left(\frac{\partial U}{\partial V}\right)_T = T(\frac{\partial P}{\partial T})_V - P$
but now I'm trying to plug in $P = \frac{nRT}{V-nb}-a(\frac{n}{V})^2$ ...
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Cubic nature of van der Waals' gas equation
$V_m^3-\dfrac{RT+bP}{P}V_m^2+\dfrac{a}{P}V_m-\dfrac{ab}{P}=0$
So, At $T<T_c$ the above equation has three real roots say $V_1,V_2,V_3$, my doubt is what does this mean physically because for some ...
- 139
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Why do we use the ratio of Critical Pressure and Critical Temperature to calculate size of a gas molecule?
Our teacher explained that using the ratio of Critical Pressure and Critical Temperature is preferred over Critical Volume to calculate the size of a gas molecule when all these quantities are taken ...
- 11
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1
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651
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If a = 0 for a Van der Waals gas, what does that signify?
I know that if $a = 0$ for a gas at certain temperature and pressure, it means that the molecules of gas have almost no attractive forces acting between them.
But does that also mean that the ...
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Should there be a better explanation on Van Der Waals force? [duplicate]
The explanation on how Van der Waals force forms is this: Van der Waals forces consist of induced, temporary dipoles between neighbouring molecules. These are caused by constantly shifting electron ...
- 171
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558
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interconverting Van Der Waal's equation for real gases from number of molecules to density
I want to ask a question about Van Der Waal's equation for real gases.
I was shown the following formula for real gases (VDW) which accounts for the liquification of water vapour which is not possible ...
- 1,240
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2k
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What is the value of isothermal compressibility of a van der Waals gas at critical point?
For a van der Waals gas, isothermal compressibility is $$\kappa=\frac{V^2(V-nb)^2}{nRTV^3-2an^2(V-nb)^2}$$ If one substitutes the values of critical temperature and volume in this formula, isothermal ...
2
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323
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Why is it experimentally difficult to accurately find the critical volume of a real gas?
I was reading up on the derivation of the values of various critical state functions( $\ce{Vc}$, $\ce{pc}$ and $\ce{Tc}$) from the Van der Waals equation (Physical Chemistry by G.W. Castellan). There, ...
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Finding (∂U/∂V )T = n^2a/V^2 for a van der Waals gas [closed]
$\displaystyle dU = \left(\frac{\partial U}{\partial T}\right)_V dT + \left(\frac{\partial U}{\partial V}\right)_T dV \to dU = C_v dT - C_v\left(\frac{\partial T}{\partial V}\right)_U dV$
Not sure ...
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How are the Van der Waals constants a and b related to each other?
I know that the constant $a$ represents the attractive forces between the molecules while the constant $b$ represents the size/repulsion between them. Does that mean that $a$ and $b$ are "...
- 201
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40k
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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 ...
- 863
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2k
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Validity of van der Waals equation [duplicate]
Van der Waals had stated that at high pressure, pressure exerted by ideal gas on the walls of container is more than real gas.
However in this graph, one can clearly see that, the at high pressure ...
- 119
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1
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5k
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How are van der Waals parameters determined experimentally?
If the ideal gas law $PV=nRT$ is not enough, as a second approximation the van der Waals equation
$$\left(P+a\frac{n^2}{V}\right)\left(V-nb\right)=nRT$$
is applied. The constants $a$ and $b$ are van ...
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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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