Van der waals Definition and 128 Threads

How would I go about calculating the units for the van der waals constants if I have 2 unknowns? (a and b) (P + a (n/V)^2) (V - n b) = n R T p=Pressure v=Volume n=moles R=gas constant T=temperature

Homework Statement If the compressability factor is given at a certain temperature as a function of pressure: Z(T) = 1+αP+βP2 find α and β in the form α(a, b, T) and β(a, b, T) where a and b are the van der waals coefficients. Homework Equations nRT=(P+a(n/V)2))(V-nb) Z=PV/nRT The Attempt...

Hey, I was hoping to be directed to some literature regarding the van der waals forces between a particle and a surface. I have found lots of models regarding particle-particle forces but no extensions of this. Thanks

There is a silly detail about the interpretation of the Van der Waals (VDW) equation that I cannot fully understand. Say we have the Van der Waals equation for one mole: (P + a / V^2 ) (V - b) = RT The usual interpretation is that if you start from the ideal gas law PV=RT, you have to...

the van der waals equation of state is given by (p+an^2/v^2)(v-nb)=nRT.how to show that for a gas obeying the above equation of state (∂Cv/∂V) (taking temperature constant)=0?

Homework Statement Taken from 'Concepts in Thermal Physics': Homework Equations The Attempt at a Solution For the step highlighted in red, why does the '-1' go into the integrand?

Homework Statement Taken from Concepts in thermal Physics: Homework Equations The Attempt at a Solution Shouldn't the van der waal's equation be: p = \frac{RT}{V_m -b} - \frac{a}{V_m^2} pV_m = \frac{VRT}{V_m -b} - \frac{a}{V_m}

Are van der waals forces between two molecules stronger in air of in water (as a medium)?

[b]1. Find an expression that relates T and V in a process in which the entropy S is constant, by doing the following: a) From thermodynamic identity dS=(1/t)dU + (p/v)dV find the expression for dS as a function of T and V (and dT and dV). b) Integrate the expression found in (a)...

Homework Statement Why does the Van der Waals equation adjust pressure up and volume down? Homework Equations (P + a)(V-b) = nRT (overly simplified, but it gets the point across). The Attempt at a Solution Okay. Volume refers to total free volume in a container in the context...

The problem reads: Consider a gas with constant specific heat cv and the van der waals equation of state (P+ a/v2)(v-b)=RT , where v=V/n A) Find du and the specific internal energy u=U/n B) Find ds and the specifi entropy s=S/n Here's what I've tried so far: A) I took the initial...

Homework Statement In the VDW eqn of state, ##(P + a/v^2)(v-b)=RT## write Pv as a function of {P,T} and by expanding the result in powers of P or otherwise show that the first terms of a Virial expansion in powers of P for a VDW gas are given by $$Pv = RT + \left(b - \frac{a}{RT}\right)P +...

Homework Statement Hi guys, I'm stuck on 2 parts for now of the following problem that appeared in an exam I totally bombed: Given the equation ##s=s_0+R\ln \left [ C(v-b)\left (u + \frac{a}{v} \right )^{5/2} \right ]##, 1)Calculate ##u(v,T)## 2)Calculate f in its natural variables (the...

Does anyone have a reference for experimental and/or estimated Van der Waals radius for the molecule hydrogen deuteride ? Symbolically, this would be a proton {(p)e-} + {(np)e-} deuterium. I would like to know how closely the two atoms can approach each other to maintain the stable state of a...

Hello! Today I've learned that when a Van der Waals gas undergoes a free expansion, it cools down a bit. :bugeye: This is in contrast with the ideal gas in which case since it does no work and since the process is adiabatic, the internal energy of the ideal gas remains unchanged by the...

Hi everyone I'd like to know the Lennard-Jones potential energy is just for symmetric particles or we can use it for asymmetric forces too? If not how can I define the potential energy between two asymmetric particles? Thanks

Homework Statement Calculate the molar volume using the van der Waals equation of a gas at P=3000psia, T=60F. The critical pressure and temperature, Pc and Tc, are Pc=408psia, Tc=504F. Homework Equations The given van der Waals equations(s): (P+a/Vm^2)(Vm-b)=RT ----(1)...

I'm so close to being done in class, though this has thrown me for a loop could anyone help me please?Does the picture show up on here?

From van der Waals , (P+a/v^2)(v-b)=RT, At critical temperature, I get (∂P/∂V)at constant temperature =0 and (∂^2P/∂V^2) at constant temperature ,T=0. then critical pressure,P = a/(27b^2)--------1 critical volume,v=3b-----------2 critical temperature=8a/(27Rb)----------3 then simultaneous...

http://en.wikipedia.org/wiki/Van_der_Waals_equation (the graph of Maxwell equal area rule) When the temperature is under the critical temperature, then at certain pressure, there will be three possible point for the volume of the system. What does that mean? Do they mean the volume of the...

[P + (n2a/V2)](V - nb) = nRT What is the P represent? Is the pressure of ideal gas or the pressure we can measure from the real gas? Consider now it is the pressure of ideal gas but how do we get the value of P from an experiment of real gas? What if it is the pressure of real gas then why do...

Homework Statement An AFM tip has a spring constant k, a colloidal bead with radius r is glues onto the cantilever tip. Derive an expression and plot the deformation of the cantilever spring, Δx, as a function of distance the tip of the cantilever is moved towards another bead of the same...

Homework Statement Based on values for the Van der Waals equation tabulated in Table 1.6 in appendix A, determine an approximate molecular volume for CCl4 and CH4. Rationalize these values based on reasonable bond lengths and other parameters. The Lennard-Jones potential energy function is...

solving for "b" with van der Waals 1. Homework Statement The problem gives me "a", the temperature, volume, number of moles, and pressure. It asks me to solve for "b". I have set up the equation to solve for b, and done it. The answer comes out with the right units but it is negative...

Homework Statement Show that at constant volume V and temperature T but decreasing number N=n*N_{A} of particles the Van der Waals equation of state approaches the equation of state of an ideal gas. Hint: Rearrange the equation of state into the explicit functional form P=P(v,T) and use x=1/v...

Why does the Van der Waals forces of hydrogen weakest in liquid state?

Homework Statement A real gas obeys Van der Waals‟ equation, which for one mole of gas is (p + A/V2)(V-B) = RT and its internal energy is given by U = CvT - A/V where the molar heat capacity at constant volume, Cv , is independent of the temperature and pressure. Show that the relation...

Homework Statement (P+ an^2/V^2)(V-nb) = nRT I'm having some problems in understanding the above equation. firstly, PV=nRT holds for ideal P and V , so after correction we are writing ideal P and V in terms of measured P and V right? secondly V-nb is the actual volume not the ideal...

I need to report about the Van der Waals interaction in our Quantum Mechanics class. Can someone please help me sort things out about Van der Waals interaction? How do go think should I go about it? In our book, the only thing discussed is the Van der Waals interaction between two hydrogen atom...

Hi Is there an eqauation to work out the Van Der Waals Force between solids? I am enquiring this in relation to how a gecko is able to walk up a wall. I have done some research and it says that a gecko can walk up walls because of Van Der Waals forces, I want to know is there an equation...

Homework Statement I've put all the information on the picture as i already created on there in an attempt to help brain storm some ideas that didn't work ... http://dl.dropbox.com/u/48169762/Capture.PNG Homework Equations All on picture :) http://dl.dropbox.com/u/48169762/Capture.PNG The...

Given that the Van Der Waals equation is (p + (an^2)/v^2)(v-nb)=nRT where n,a,R and b are constants... How to we find the derivative of p wrt v ? How to find the derivative of p wrt T without further differentiation ?? Can anyone teach me how to do this question ? Sincerly thanks~

what are the main drawbacks of the van der waals equation of state for real gases and how are they corrected?

Homework Statement I'm trying to find dT/dVm for the van der waals equation. I was looking at http://courses.washington.edu/bhrchem/c456/vdw_jtc.pdf" page, but I'm confused about how they reached their result: The Attempt at a Solution I honestly have no idea what they did. dT/dVm of...

Can someone enlighten me about the quantum level explanations for the following: 1. Adhesion between two substances 2. Cohesion within a substance 3. Strength of a substance (as in tensile strength, compressive strength and shear strength) 4. Stiffness of a substance (as in Youngs modulus...

Just wondering, for van der waals equation, the real pressure is smaller than the ideal pressure and the real volume is smaller than the ideal volume?

Does the compressibility factor of a gas say anything about Van der Waals constants?

Homework Statement Suppose the equation of state of a gas is Beta p=rho/(1-b rho) - beta a rho^2 where beta=1/kb T, b is a constant and rho is the molecular density, N/V. The internal energy of this gas is given by U=(5/2)N kb T - N a rho Determine the final internal energy of the gas...

Homework Statement Hi there. I have this problem which I'm trying to solve. Its from callen, it says: Two ideal van der Walls fluids are contained in a cylinder, sparated by an internal moveable piston. There is one mole of each fluid, and the two fluids have the same values of the van der...

hi. first of all i am a little bit confused about the difference between casimir and van der waals forces? isn't it so, that both forces are consequences of Lifgarbagez's theory? so how can you distinguish between them? another question I asked myself is, how do Casimir and Van der Waals force...

Hello So I have a lab exam in Joule-Thomson effect and I have given values for a and b for VdW equation of state for nitrogen and carbon dioxide. When I take the critical temp. and pressure and put it in the equations: a=\frac{27(T_c R)^2}{64 p_c} and b=\frac{T_c}{8p_c} b gives...

For this problem, I'm really jst trying to figure out everything that is going on and then I can simply follow through with the derivatives once I know what I'm working with. Q: For the van der Waals gas, introduce the free energy as F = U – TS and verify that its derivatives over V and T...

Homework Statement So basically I'm sort of unclear as to what van der walls interactions are and how they occur...like I know that they're a type of noncovalent bond that occurs between identical groups in two molecules. Like, how do the partial charges appear? (e.g. let's say there are 2...

For an assignment, I am graphing using the Van der Waals equation. I am meant to find graph PV (y-axis) over (P). However, I am not sure why. On the internet, most other graphs also use these axes. Why do you use PV though? I am getting a graph that generally similar to those on the internet...

Hi I was studding Van-der-waals equation for real gases when I got in my mind two questions that i couldn't get a sufficient answer for from my professors, hope you have a better explanations : 1- Why there is critical point? It was shocking for me to know that there is a particular...

Hi everyone, Struggling with the following question - maths and physics never been my strongest subjects. Thanks in advance 1. An equation of state that has been used to model the behaviour of a fixed amount of a real gas is: (P+a/v2)(v-b)=ZT In the equation Z, a, b are constants, and...

Hi could someone please give me a run down of these forces? I'm studying them atm but do not really understand them. also, are double and triple bonds representations of 2electrons being shared and 3 electrons being shared? also, when drawing electrondot diagrams for molecules ect. are ionics...

Is Van Der Waals forces just a name for all intermolecular forces that exist between molecules or does it only refer to certain types of intermolecular forces?

Solving for volume in Van der Waals Equation?? Homework Statement Determine the specific volume, v (volume per mass[m^3/kg]) of a water steam at a pressure of 100kPa and a temperature of 500 degrees Celsius by assuming an ideal gas (pV = nRT) and by using the van der Waals equation for n...

1.Why does boiling point depend on weight ? 2.Does the vanderwall force depend on weight ?