# Questions tagged [physical-chemistry]

The study of chemical systems using the laws and concepts of physics. This usually requires the techniques of thermodynamics, statistical mechanics and quantum mechanics.

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### In an isothermal process, how can the change in internal energy be 0?

It was written in my textbook, $$\mathrm{d}U = \left(\frac{\partial U}{\partial T}\right)_V \mathrm{d}T +\left(\frac{\partial U}{\partial V}\right)_T \mathrm{d}V$$ If the process is isothermal,...
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### Outline the steps involved in the Hartree–Fock method for the calculation of molecular electronic structure [duplicate]

I understand that the steps of the self-consistent method are as follows: guess the form of Psi(r) use psi(r) to evaluate for V1eff(r1) then solve for a new psi(r) the two wavefunctions tend to ...
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### Ellingham Diagram

My textbook says the following about the Ellingham diagram: Each plot is a straight line except when some change in phase ($\ce{s -> liq}$ or $\ce{liq -> g}$) takes place. The temperature at ...
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### Inductively Coupled Plasma and Mass Spectrometry

I was doing some homework and I was reading about how ICP is suitable for mass spectrometry and it said how its high temperature favours ionization which is good in MS. But also, because the ...
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### Difference between Particle in a Box and Harmonic Oscillator approximations

Why in the particle in a box model do the values of n begin at 1 but in the harmonic oscillator they begin at 0? I understand what the wave-functions and their corresponding probabilities look like ...
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### Why when deriving the Clapeyron equation can you assume that dH = dq, as surely the pressure is not constant?

Part of the Clapeyron equation involves replacing $\Delta S$ with $\Delta H/T$. I can see the step from $\Delta S$ to $\Delta q/T$ but I'm not sure why you can replace $\Delta q$ with $\Delta H$. From ...
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### Does H2C=C=C=CH2 lie in the same plane? [closed]

explain in terms of bonding theory why all atoms H2C=C=C=CH2 must lie in the same plane
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### Calculating partial pressure with 3 equilibrium equations [closed]

So my friend had sent this question to me some days ago and it seems I still am not able to solve it. I am confused whether the amount of A that dissociates in the first equation would account for the ...
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### Atomic structure what is binding and ionisation energy [closed]

What is the difference between ionisation energy and binding energy if not then what is similarity between them
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### Can Electronegativity be explained through QM? [closed]

Even as senior in high school, I still find chemistry quite intimidating, partly due to how vast it is and partly because I don't understand when something stated in Chemistry is experimentally ...
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### Determine bond length via rotational spectroscopy

Estimate the bond length of 12C16O (pure rotational spectrum) given J''=3 (15.356 cm-1) and J'=9 (38.356) I understand that the first step is the calculate the rotational constant. So to do this I ...
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### Order of reaction in adsorption process

(1) $\ce{PH3(g) <=>[W]PH3(adsorption)->[W]P(s) + 3/2 H2(g)}$ The decomposition of phosphine on tungsten surface at low pressure is a pseudo first order reaction. This is because the rate of ...
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### The reaction rate when the rate-determining step has a back reaction

For some reason, I am reviewing general chemistry and I find that the elementary reaction for the rate-determining step (RDS) is assumed to be irreversible, that is, single arrow, in all questions ...
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### Degree of dissociation of weak electrolyte at infinite dilution

Why the degree of dissociation of weak electrolyte is 1 at infinite dilution and how do we get the result? Like I know that at infinite dilution the concentration of solution is 0 but what does that ...
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### What is J in the rigid rotor model?

In my class notes regarding the rigid rotor model, J is described as simply the angular momentum (replacing roe or p) and is also referred to as the angular momentum quantum number. Are these two ...
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### What is the difference between dynamical and non-dynamical correlation and which one is accounted for in Hartree-Fock theory? [duplicate]

It is my understanding that dynamical is related to the movement of individual electrons. I don't fully understand what this means though. Non-dynamical correlation is still very unclear from my ...
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### Why can a wave-function be written as a product of 1-electron wave-functions?

Why can a wavefunction be written as a product of 1-electron wave-functions when making approximations to solve atoms other than hydrogen? (ie. helium) We used this when solving multielectron systems ...
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### Finding the wavelength of maximum absorption and Crystal Field Splitting of [Ni(H2O)6]2+

(I haven't been here for a long time, so tell me if my formatting is fine) Given The $\ce{[Ni(H2O)6]^2+}$ complex appears green in solution from the transmitted light. Estimate the wavelength of ...
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### Can we break double bonds by using laser and heat?

If it is possible then give an example for it. That chemical reaction is in this process. step 1: {Reactant + heat(sunlight)} gives weakened bonded product1 step 2: {product1 + laser} gives {one solid ...
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### Is dz2 orbital having lobe in z axis direction is larger than other d orbitals? [closed]

I have seen in one video that dz^2 orbital is formed with d(x2-z2) and d(y2-z2) and hence its lobe in z axis become large due to overlap so is it mean that dz2 lobe in direction of z axis is larger ...
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### Neither Raman nor IR Active vibrational modes of water [closed]

How can we find vibration modes of water that are not in IR and Raman spectroscopy? I thought these modes creat when a transition happens between 2 modes i.e from mode to another mode.
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### Higher Experimental Optical activity compared to literature values [closed]

If you have a sample of an optically active substance it has a specific angle of rotation. Lets say the substance I produced had a value of 56 degrees but the literature value for my substance should ...
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### Relation of temperature and intensive property [closed]

I came across a question that inquired about whether there exists any intensive property of a system, that is independent of temperature and then seeks proof for the presence/absence of such ...
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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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### What all information can be gathered qualitatively from the radial distribution functions of a molecule?

Apart from knowing the radius of coordination shells and the probability of finding, is there any other thermodynamic information we can gather by looking at radial distribution functions of a ...
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### What does it mean to balance a redox reaction in acidic or basic mediums? [closed]

Until now it was clear to me what balancing a reaction was. Balancing redox reaction also make sense to me. What does it mean to balance a redox reaction in acidic or basic medium?
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### Clarification on temperature-composition phase diagrams of a Binary Mixture

After watching this video: https://www.youtube.com/watch?v=SPrybbPdVDQ, I have come to the conclusion that on a temperature-composition curve(for two components, $\mathrm{A}$ and $\mathrm{B}$), there ...
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### How much CO2 can I fit in a 0.5 L plastic bottle?

Let's say I have a 50 lb CO2 tank which can probably contain about 1000 L of the gas at 122 atm. Suppose I want to use the tank to fill a 0.5 L plastic bottle which only has air in it. We know that ...
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### What is the product of the reaction between hydrogen peroxide and ammonium thiocyanate?

Title. I saw a video showing 30% hydrogen peroxide being dripped onto ammonium thiocyanate. https://www.youtube.com/watch?v=fQju2e8CMPY I am wondering what the product of that reaction is. The people ...