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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156 views

Does an orbital have its own energy, separate from the electron? Can I picture them as a entity independent from the hosted particle? [closed]

Does an orbital have its own energy, separate from the electron? If so, is it possible for an electron to have a different energy than the orbital it occupies?
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Particle in a box with different barriers between two molecules

I'm trying to understand different ways to solve a PIB model. I'm given a molecule with a tetrahedral geometry and there are two related ground states - electron pair pointing up or down. I'm being ...
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Internal energy of a gas

My professor says that the internal energy of a gas is the sum of its kinetic energy and potential energy: $U = E_k + E_p$. It also says that the root-mean-square speed of gas molecules is $v_{rms}=\...
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What is the edge length of ZnS, given the radii of Zn and S ions? [closed]

What is the edge length of $\ce{ZnS}$, given the radii of $\ce{Zn^2+}$ and $\ce{S^2-}$ ions?
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What is heterogeneous catalysis in gas phase?

Give examples of heterogeneous catalysis (i) in gas phase and (ii) in liquid phase. Now, I came to know that heterogeneous catalysis involves different phases between the catalyst used and the ...
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Overlap integrals in Hückel theory

In Hückel theory we are only interested in π systems, where $\mathrm p_z$ orbitals overlap. One of the approximations in Hückel theory is that the overlapping $\mathrm p_z$ orbitals are orthonormal: $...
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27 views

Pressure of gas increases with temperature at constant volume due to

At constant volume, for a fixed number of moles of gas the pressure increases with rise of temperature due to: I think with rise of temperature, entropy of system will increase because $\Delta S=nc_V\...
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Why does high blood gas partition coefficient of a inhalational anaesthetic drug mean slower induction of anesthesia?

High blood gas partition coefficient of a drug corresponds to higher solubility of the drug in blood leading to high concentration of the drug in blood with respect to gas (air in alveoli). If the ...
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74 views

Find order of reaction 2A → B + C

Derive the integrated rate expression for a reaction of type: $$\ce{2A -> B + C}$$ I first need to determine the order of the reaction in order to find integrated rate law of that particular order....
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Constructing phase diagram given temperature-concentration-phase data

This question may look straightforward to be answered but somehow I can not figure it. I received these papers [1-2]. Here, the papers (both papers study same system) provide complete information of ...
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143 views

How do we obtain the π molecular orbitals for allene via Hückel theory?

For a conjugated system, for instance 1,3-butadiene, we can try to obtain the π molecular orbital energies and wavefunctions via Hückel theory. In our given molecule, there are 4 interacting Pz ...
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Effect of pressure on transition temperature

I was wondering if someone can explain why the answer to the following question is volume instead of the others. If pressure has no effect on the transition temperature between two crystalline forms ...
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Orbital Approximation

We determined the hydrogen wavefunctions exactly, and the orbital approximation says that we approximate the orbitals of multi-electron atoms with hydrogen wavefunctions. How do we know that this is ...
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Different direction of dipole moment in physics and chemistry [duplicate]

In chemistry, we learn that dipole moment tells us about measure of polarity in a molecule. In books, it is written that "conventionlly the direction of dipole moment is from electropositive to ...
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1answer
34 views

Can Ferrofluids vaporise to gaseous state and Condense back to liquid state and do it many times over? [closed]

Here is the Link for Ferrofluids for basic idea. After going through this Wiki link, probably many people will come to a conclusion like when Ferrofluid boils, its carrier liquid vaporises and nano ...
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What does the phase diagram mean by “liquid” at NTP? (The liquid and vapor coexist even when the situation is not on the curve)

[Solved. For anyone who is also confused, see the comments under Poutnik's answer. As Poutnik reminds me, remember there is no air involved. I successfully picture that with the piston experiment in ...
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How is a reaction with more products than reactants spontaneous?

If I have a reaction that has $\Delta G^\circ = 0,$ where there are more products than reactants (for example, $\ce{A <=> 2B + 2C}),$ then if I change the concentration of all the reactants and ...
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104 views

Percent degree of dissociation of gas by pressure

I stumbled across the following interesting problem: Assume that you have started to live on a new planet where standard pressure condition is $\pu{2 bar}$, standard concentration is $\pu{1 M},$ and ...
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Why is the viscosity of water and ethanol lower than that of a water-ethanol mixture?

We found in an experiment using Ostwalds method that ethanol is more viscous than water, which is already surprising as water has stronger intermolecular bonds than ethanol as @MaxW pointed out. The ...
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1answer
42 views

Does evaporation occur while boiling as well? [closed]

If evaporation were to occur when a liquid was being boiled, then the amount of liquid changing phase would also depend on the surface area of the liquid exposed to the atmosphere (as evaporation rate ...
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How to calculate “volume of gas” generated by a given ion ore in a blast furnace? [closed]

A blast furnace makes pig iron containing $3.6\% \; \ce{C}$, $1.4\% \; \ce{Si}$, and $95\% \; \ce{Fe}$. The ore is $80\% \; \ce{Fe2O3}$, $12\% \; \ce{SiO2}$, and $\ce{Al2O3}$. The blast furnace gas ...
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Dipole moment difference between ch2f2 and ch3f [duplicate]

In CH3F and CH2F2 the net dipole moment increases from 1.82 to 1.97 while in all other halogen substituted carbon atoms the dipole moment decreases. In the case of CH3Cl and CH3F the chlorine ...
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Pressure of a system of particles

I'll derive the pressure of a system of particles, which would be used in a MD simulation for example, according to Allen's Computer Simulation of Liquids and show where my issue is. Consider a ...
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108 views

How does polarity of a solvent increase conductance of electrolyte?

My textbook says that electrolyte ionize more in polar solvents and greater is the polarity, larger is the conductance. But if polar solvents (lets take water) causes the formation of shells around ...
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Generating hybrid atomic orbitals for Boron

My professor was showing us how to form hybrid atomic orbitals for Boron by taking a linear combination of rotated 2p orbitals and 2s orbitals (of Boron). This was done in a particular manner such ...
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Temperature dependence of emission lines from gases, for example, neon

Emission lines from Ne are frequently used as wavelength standards in spectroscopy. Reading around Wikipedia, I found about the Paschen law regarding the voltage required to start a discharge. My ...
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232 views

Is the number of tetrahedral voids always equal to double the number of octahedral voids in any crystal?

I came accross the question whether the number of tetrahedal voids is always equal to twice the number of octahedral voids (in the case where both the voids are present). The key was given as the ...
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1answer
41 views

Does lower activation energy definitely mean higher rate?

Does lower activation energy definitely mean higher rate? For example the decomposition of $\ce{H2O2}$. Can we say it has the highest rate with the catalyst making the reaction's activation energy the ...
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Can Na2CO3 remove temporary hardness of water?

This was asked in my test and I remembered that all compounds that can remove permanent hardness of water can remove temporary hardness of water also. But my teacher marked it wrong and I cannot find ...
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Trouble understanding equation from density functional theory

In the review by Oliviera et. al., I do not understand how the authors get equation 14: \begin{equation} E[\rho]=\sum_i^Mn_i\langle\Psi_i|-\frac{1}{2}\nabla^2+v_{ext}(\vec{r})+\frac{1}{2}\int\frac{\...
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48 views

Equilibrium constant for the thermal dissociation of phosphorus pentachloride [closed]

Thermal decomposition of $\ce{PCl5}$ is studied in a closed vessel. Partial pressure of $\ce{PCl5}$ in gaseous equilibrium mixture is $\pu{1 atm}.$ $\pu{50 \%}$ $\ce{PCl5}$ dissociates. Find ...
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42 views

What is negative adsorption? [closed]

In adsorption, the concentration of adsorbate is greater on the surface. So, how is it possible that the solvent will be more on the surface and the solute (adsorbate) in the bulk… or does solute not ...
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1answer
59 views

Is this galvanic cell representation right?

Question 13. In the galvanic cell: $$\ce{Pt(s) | I2(g) | I-(aq) || Fe^3+(aq) | Fe^2+(aq) | Pt(s)}$$ Representation of anode is incorrect and cell will not work. $[\ce{Fe^3+}] = [\ce{Fe^2+}] = [\ce{I-...
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Molecular orbital diagram for I₃⁺ cation

Do I need to go through the whole process of reducible representations/projection operator method to come up with the bent SALCs for the $\ce{[I3]+}$ molecule? Or is it simpler than that?
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30 views

MO diagram for triiodide anion [duplicate]

I can't figure out this MO diagram. Are there d orbitals involved? I thought the central atom would have d orbitals participating in bonding since it has an expanded octet. For the central atom I ...
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33 views

How to graph spherical harmonics in the Mac “Grapher” application?

I was wondering if it was possible to graph the spherical harmonics in the Mac grapher app. In their manual, there is a section that talks about graphing the spherical harmonics (page 54): This is my ...
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28 views

The meaning of magnetic quantum numbers' values

The $\mathrm{m_l}$ values in quantum mechanics, $1, 0, -1$ for p orbitals for example, do they refer to specific orbitals? Like, does $\mathrm{m_l} = 1$ refer specifically to $\mathrm{p_x, m_l} = 0$ ...
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121 views

Algebraic treatment of equilibrium

This is from Laitinen and Harris, "Chemical Analysis, An Advanced Text & Reference" which describes a simple acid-base equilibrium. They derive a relation in the end directly. I haven't seen this ...
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1answer
63 views

What is the relationship between dipole moment and solubility? [closed]

I thought a large dipole moment meant the substance was polar, so I'm confused by the following statement (from Wikipedia) that "With a dipole moment of 3.92 D, acetonitrile dissolves a wide range of ...
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1answer
30 views

Conversion factor for chemical to physical scale of atomic masses

Before the 1960s chemists and physicists used to have different atomic mass tables. The main difference was that the physicists assigned the $^{16}$O as the O=16 from mass spectrometry. Chemists on ...
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Why is platinum denser than gold?

The atomic masses of gold and platinum are 196.96657 u and 195.084 u respectively, meaning that (on average) an individual gold atom is heavier than an individual platinum atom. At the same time, the ...
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Calculating Ka using Nernst Equation

I've heard multiple times that the Nernst Equation could be used to calculate K$_a$. How would one calculate the acidity constant, K$_a$, of a specific acid, using the Nernst Equation? The equilibrium ...
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How does the heat capacity of a calorimeter interact with the specific heat capacity of the water inside it?

I saw this basic calorimetry question and it included the heat capacity of the calorimeter (1550 J/°C) but it also included that there were 150 g of water inside the calorimeter as well (4.184 J/(G°C)....
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1answer
102 views

Reducing pressure in a binary liquid solution

Consider the following diagram for a binary liquid system comprised of A and B, where A is the more volatile component. My professor says Consider an isopleth from $a$ to $a_4$. At the start, the ...
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34 views

Melting point of crystalline solids

Why crystalline solids have sharp melting points but melting point of amorphous solids vary within a range? Is it because the interaction energy is equal between atoms of crystalline solids so they ...
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1answer
47 views

Why are crystalline solids anisotropic? [closed]

Why crystalline solids are anisotropic whereas amorphous solids are isotropic? Is it because in crystalline solids, X, Y and Z dimensions vary, but so does in amorphous. Please write as simple as ...
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Why thermodynamic state variables of a sytem are only defined at thermodynamic equilibrium and not during any other instant? [closed]

As you have read the title so my question is why are thermodynamic variables only meaningful when the thermodynamic system is in thermodynamic equilibrium and is always meaningless in any other case.
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65 views

Law of equivalence [closed]

100g mixture of nitrates two metals a and b is heated to constant weight containing corresponding 50g oxides of the metals {i.e METAL NITRATES(100g) --->OXIDES(50g) +(some nitrogen oxide gases) } . ...
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54 views

T∆S implies that heat flows which way?

From Schroeder's Introduction to Thermal Physics. Parts $(a)$ and $(b)$ are quite simple, and we find that $ \Delta H =-2808\ \mathrm{kJ}$ and $\Delta G =-2879\ \mathrm{kJ}$, so by $\Delta G = \Delta ...
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Conception and manufacture of the Avogadro Project's (nearly) perfect silicon sphere (and, what is “atomic feeling”?)

The Avogadro Project, an effort prior to the recent redefinition of Avogadro's constant to design a nearly perfect sphere of silicon-28, apparently relied on the fine fingers of optician Achim ...

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