Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange
Join us in building a kind, collaborative learning community via our updated Code of Conduct.

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

0
votes
0answers
12 views

THz Spectroscopy of proteins [on hold]

I want to study aqueous solutions of proteins using THz spectroscopy to gain insights about the different vibrational modes and the solvation dynamics. Can someone suggest some interesting proteins to ...
0
votes
0answers
14 views

Can oxidation peak tell anything about amount of gold deposited in cyclic voltammetry?

In doing an experiment which involved depositing gold nanoparticles by cyclic voltammetry, I was told the amount of gold that has been deposited can be estimated by comparing the size of the reduction ...
4
votes
1answer
57 views

Properties of azeotropes

Consider two liquids with vapour pressures in pure form being ${P^o}_A$ and ${P^o}_B$. ${P^o}_B >{P^o}_A$ which implies liquid B is more volatile. If the liquids formed an ideal solution, then a ...
4
votes
1answer
92 views

Balancing using oxidation number method

Balance the following equation using oxidation number method: $\ce{PbS + H2O2 -> PbSO4 + H2O}$ Attempt: I have written down the oxidation states of all atoms and we can observe reduction of ...
3
votes
1answer
54 views

Does the rate constant depend on pressure?

I have read in some books that when pressure increases, the number of effective collisions increases. Hence, $k$ depends on pressure. Is it true? If so, then why doesn't $k$ depends on concentration? ...
-1
votes
0answers
11 views

To determine rate constant using volumetric analysis [on hold]

Suppose let us take the ester hydrolysis reaction Now we have to calculate the rate constant How did they derive this formula, if so then the initial concentration ie Vo is the neutralisation of H+ ...
-2
votes
0answers
11 views

solubility product-ionic equilibrium [closed]

a solution is 0.1M in cl^-,0.01M in br^-,0.001M in I^-, agno3 is added to the solution [v mix=0].the concentration of ag+required to start precipitation of all 3 ions is [given,ksp of agcl is 10^-10,...
1
vote
0answers
46 views

Dependence of energy on a molecule's dihedral angle

I've studied the dependence of biphenyl's Energy on its dihedral angle. I know how to describe the dependence quantitatively, but still, I don't know how to explain that the potential barrier of ...
-2
votes
0answers
33 views

Determine the thermal efficiency of a boiler from given input and output steam conditions, steam flow rate and power input [closed]

An oil-fired boiler takes in feed water at 75 °C and produces wet steam at a pressure of 5 bar. The steam flow rate 1.50 t/h with a dryness fraction of 0.89. The fuel consumption rate is 6.10 kg/min ...
-1
votes
0answers
16 views

Electronic configuration of Nb and Ru [duplicate]

Why do niobium and ruthenium show exceptional electronic configuration?
-2
votes
0answers
15 views

Final ppm build up in water column [closed]

Suppose i dissolve 1ml of a 4000mg/l solution in 130 l water, how much concentration in ppm will get build up in the water column?
1
vote
0answers
25 views

Order of a complex reaction [duplicate]

Is the order of a complex reaction determined by the slowest step always? Is it so that order of a reaction is determined by rate determining step and since in a complex mechanism, we write elementary ...
-1
votes
0answers
15 views

When partially flashing ethanol and carbon dioxide, what is the ratio in the vapour? [closed]

If I have a 4-inch line that contains $\mathrm{104^\circ C}$ ethanol/$\ce{CO2}$ and it enters a $\pu{950 gal}$ flash vessel, part of it will flash into a vapour. I'm wondering what ratio of ethanol:$\...
3
votes
0answers
39 views

Oscillator strength of a transition

I am trying to compute the oscillator strength in a molecule. Therefore I've got its Energy level values plus both wave functions $\Psi_i$ and $\Psi_j$ for the transition I want to calculate the ...
1
vote
0answers
21 views

Where does hydrogen evolution occur when aluminium amalgam is placed in water - aluminium or mercury?

Let's say a drop mercury is placed on clean aluminium sheet; mercury amalgam is formed. The solubility of aluminium in mercury and vise versa at room temperature is fairly low. If the entire sheet is ...
0
votes
1answer
25 views

Will a container made of ice hold an alcoholic beverage that is below freezing in an environment that is also below freezing?

This very specific question that came after saw I a travel episode where they served alcoholic beverages in ice glasses in an ice bar. I wondered if the drink contents would stay in the glass (of ice) ...
11
votes
2answers
771 views

Is there a physical explanation why benzene's pi molecular orbitals in a Frost circle are degenerate but pyridine's are not?

From here, the Frost Circles for both benzene and pyridine: The $\pi$-MOs formed by 6 $\pi$-AOs of an aromatic ring are: Listed with respect to the ordering in the above image, these MOs in benzene'...
-1
votes
1answer
44 views

Molecular Geometry [duplicate]

Why is it that for a molecule with trigonal bipyramidal geometry, the lone pair is located in the equatorial region whereas for a molecular with an octahedral geometry, the lone pair is located in the ...
1
vote
1answer
36 views

Graphite: Thermal and electrical conductivity

I recently encounter this question: Compare, while providing an explanation, the thermal and electrical conductivity of graphite to that of diamond. Provided answer: Graphite conducts electricity(...
2
votes
0answers
51 views

Hückel method for biphenyl

I am trying to calculate the energy levels of biphenyl (see picture below) using Hückel method. Since this is my first time using Hückel I am a little confused. Biphenyl has 12 carbon atoms, ...
-1
votes
0answers
30 views

Proof for equation of state for moist atmosphere [closed]

If $e$ and $p$ are vapor pressure of water and total pressure of moist air respectively, then the equation of state for moist atmosphere can be written as $$PV = RT[1 + 0.62 \frac{e}{p}]$$ Can anyone ...
0
votes
0answers
25 views

Excitation energy of a symmetric molecule [closed]

Let's suppose I have a symmetric molecule e.g. biphenyl (The dihedral angle etc. shall be negligible.) When I want to calculate its excitation energies analytically the easiest way would be something ...
1
vote
0answers
17 views

Distinguish between two possible configurations for angular momentum in carbon atom

Consider the possible values of $S$ and $L$ for carbon configuration $1s^2 2s^2 2p^2$ and the corresponding rapresentations with arrows indicating the spins (consider only $S=0,L=0$ and $S=0,L=2$, as ...
0
votes
1answer
44 views

Why is the melting point of hydrogen fluoride lower than that of ammonia?

The melting point of hydrogen fluoride is -83.6°C, as compared to that of ammonia, which is -77.73°C. How does this make any sense? Both hydrogen fluoride and ammonia show hydrogen bonding, which "...
4
votes
1answer
48 views

In Bohr's model what is angular momentum in the lowest orbital?

Angular momentum is given by: $n\frac{h}{2\pi}$ where $n=1,2,3...$ And angular momentum is also given by: $\sqrt{l(l+1)}\frac{h}{2\pi}$ By the first equation angular momentum should be $\frac{h}{2\...
0
votes
0answers
25 views

Is H2O the only compound with a density anomaly? [duplicate]

My question is simple: are there any elements, compounds or materials other than water (H2O) which have a density anomaly characterized by a turning point in the τ-ρ curve?
0
votes
1answer
81 views

Relative molecular mass of an unknown gas in a mixture

A gaseous mixture contains oxygen and another unknown gas in the molar ratio of 4:1 diffuses through a porous plug into 245 seconds, under similar conditions same volume of oxygen takes 220 seconds to ...
-1
votes
1answer
47 views

Is the stoichiometric coefficient equivalent to the mole fraction?

I have a small problem to understand (or distinguish between) two concepts of free mixing enthalpy. In several textbooks, I found the following formula for the molar free mixing enthalpy (binary ...
0
votes
0answers
58 views

distillation of aqueous CAN solution for the purpose of a reversible and strong endothermic reaction in cool packs

I know calcium ammonium nitrate (CAN) is used for cold packs. By bending a small metal plate the salt gets dissolved in water (separated pack) and this process is endothermic. I would like to heat ...
1
vote
0answers
45 views

The nature of Chemical Bonds [closed]

It was nearly a year ago when I appeared for my first interview through the KVPY (a research oriented scholarship exam) when one of the questions the panel asked me was : What is a chemical bond? ...
6
votes
1answer
104 views

Do molecules change shape when they become vibrationally excited?

In quantum mechanics we learn the the classical picture of a vibrational excitation is wrong. The atoms will 'vibrate' only while the molecule is in a coherent superposition of two vibrational states, ...
4
votes
1answer
78 views

“Proof” that the chemical potential is less than zero for irreversible material changes

From Levine's Physical Chemistry: 1) In a closed system, $\mathrm dG = -S\,\mathrm dT + V\,\mathrm dP$ not only applies to constant composition but also reversible changes in composition. 2) For an ...
-3
votes
1answer
28 views

How can prepare ppb solution of sodium [closed]

How can prepare 1000ppb solution of sodium from sodium chloride salt in one litre.
0
votes
1answer
35 views

How can I prevent the effervescence of a solvent during evaporation?

How can I prevent the effervescence of a solvent like petroleum ether when I evaporate it on a water path?
-1
votes
1answer
37 views

Coordination number of spheres (all identical) in hexagonal close packing (HCP)

I was revising solid state chapter when I came across this question What is the maximum coordination number of an atom in a hcp crystal structure of an element? The word 'maximum' drew my ...
5
votes
0answers
46 views

How to calculate a molecule's oscillator strength?

I was wondering how to calculate a molecule's (e.g. biphenyl) oscillator strength using a very simplified model. If I want to calculate a molecule's excited states a good start is something like a ...
1
vote
4answers
111 views

A simple equilibrium problem

Take the following simple equilibrium: $$\ce{CH3COOH + H2O <=> H3O+ + CH3COO-}$$ Ethanoic acid will act as a typical Brønsted-Lowry acid and donate a proton to water, forming a conjugate acid-...
0
votes
0answers
35 views

Calculation Radial distribution function using Potential

I am trying to understand an article where it is describing the accuracy of a potential function obtained via a NN (neural network). To test the ability of the NN potential to describe also ...
2
votes
1answer
51 views

Why are the concentrations in the equilibrium constant multiplied? [duplicate]

$$\alpha\,\mathrm{A}+\beta\,\mathrm{B}+\cdots\rightleftharpoons \rho\,\mathrm{R}+\sigma\,\mathrm{S}+\cdots$$ The equilibrium constant for this reaction can be calculated using the following formula: $...
0
votes
1answer
37 views

What does it mean for an equillibrium to move? [duplicate]

Le Chatelier's principle was described to me as: If a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium moves to counteract the change. I do not understand ...
2
votes
1answer
51 views

Calculate force on atoms given the energy of configuration, trajectory of simulation and position of atoms in each frame

Background I am using a neural network to calculate the potential energy of atoms in a configuration and then adding energy of all atoms to compare it with the true energy of the configuration(label) ...
1
vote
2answers
45 views

Why do we use the word phase and state of matter so interchangeably? [closed]

I would be happy if someone explains me why the word "phase" and "state of matter" is used so interchangeably.Lets say we have HBr and another compound in the system both gases.Then am I to take two ...
2
votes
1answer
80 views

Why does the liquid in an Oralmedic stick flow uphill after I turn it upside-down?

I was experimenting with an Oralmedic stick, which is basically a cotton swab with a hollow stick that has liquid medicine inside, and observed something very unexpected. I followed the usage ...
0
votes
0answers
22 views

Cell Potential of a cell with a reference electrode

In my textbook there is a question asking about the cell potential of a cell that has a reference electrode. It gives me the equation: $\ce {Ag_2CrO_4(s) + 2e^- -> 2Ag(s) + CrO_4^2-(aq)}$ and ...
1
vote
1answer
49 views

Why does ethane release more energy than ethyne when burned?

My book explains that since ethane contains a single bond, ethene contains a double bond, and ethyne contains a triple bond, and that when burned ethane releases the most energy because "the fact that ...
0
votes
0answers
21 views

How to calculate the enthalpy of fusion at a different temperature?

The heat capacity of liquid iodine is $80.7$ $\ce{J*K^{-1}*mol^{-1}}$, and its enthalpy of vaporization is $41.96$ kJ $\ce{*mol^{-1}}$ at its boiling point ($184.3$ $\ce{^oC}$). Furthermore, the ...
3
votes
1answer
174 views

Which formula can be used to calculate the exact hydronium concentration present in sodium hydrogen carbonate solution?

Which formula can be used to calculate the exact hydronium concentration present in sodium hydrogen carbonate solution ? $$\ce{[H3O+]}=\sqrt{K_\mathrm{a1}K_\mathrm{a2}}$$ $$[\ce{H3O+}]=\sqrt{\frac{...
-2
votes
2answers
39 views

Why does the compound formed after a coordinate bond have a net charge? [closed]

Why does the molecule have net positive charge?
3
votes
0answers
67 views

Calculating excitation energies of a molecule

I am trying to calculate the excitation energies for the first three transitions of a molecule which is made up by a chain of k phenyl rings, where k shall be between 1 and 8. The angle between each ...
4
votes
1answer
87 views

Knowing that CI is variational for any basis set, why is coupled-cluster variational in the full correlation limit?

This is the question asked in Martin's comment to my answer to: Why is Coupled Cluster not variational? In the comment I was also asked to provide a publication as a reference: