Molecules Definition and 543 Threads

If QM is a statistical model to approximate something underlying space time we don't quite understand yet, and there is a complex geometry underlying space time, is it possible to find other ways to simplify molecular optimizations and electron interactions in computational chemistry using...

Homework Statement Homework Equations Please see below. The Attempt at a Solution I'm probably being really stupid here but how can the number of molecules equal If we integrate we get a volume multiplied by density, how can that equal a number of particles?

Dear Everyone, If we have a set of diatomic molecules consisting of a common element (F atom) and the other atoms belong to the same group; which are: BeF, MgF, CaF, SrF, and BaF. We want to study the electronic structure of these molecules by comparing their molecular electronic states. We...

(@mfb posted an article about this here, I think it deserves an own thread, and I did not find one, so I start one :smile:) The comet-like composition of a protoplanetary disk as revealed by complex cyanides Karin I. Öberg, Viviana V. Guzmán, Kenji Furuya, Chunhua Qi, Yuri Aikawa, Sean M...

Why is the average kinetic energy of the molecules a cold liquid less? As the temperature of a liquid decreases, the average kinetic energy of its molecules reduce. What is the reason behind this?

Hello Everyone, A little question regarding the TDMs between two different electronic states of a diatomic molecule. If I am calculating the TDM from state A to state B, is it the same if we are calculating the TDM from state B to state A? Are these two transitions the same? Thank you so much...

Hi there! Is there an online, hopefully free resource (preferably textbook) that details the process of molecular modeling? Specifically, computationally performing geometry optimizations, vibrational analyses, calculating Raman spectra, detailing the theory behind Hartree-Fock, DFT, post-HF...

Homework Statement According to statistical mechanics, the average kinetic energy of a particle at temperature T is 3kT/2, where k is the Boltzmann constant. What is the average de Broglie wavelength of nitrogen molecules at room temperature? Homework Equations KE = 3kt/2 = p2/2m λ = h / p...

Homework Statement A mixture of two substances exists on a cubic lattice of N sites, each of which is occupied by either an A molecule or a B molecule. The number of A molecules is NA and the number of B molecules is NB, such that NA + NB = N. The energy of interaction is k_BT\chi_{AA} between...

I would like to understand how LCAO may be used to construct the matrix to be solved for the molecular orbitals of two cases of molecules: 1) small molecules like H3 (or H3+, HF2-, H2O, CH4, etc. 2) groups or parts of molecules with delocalized pi-systems (including linear and cyclic...

Hi everyone! I am researching on Metals Work functions, and I need a table of distances between molecules! I searched on the web almost a week, but I didn't found at least A table. Please help me! If it is in a book, tell me the name of the book, or tell me where can I find it. Any help would...

Homework Statement Estimate the energies of interaction at 25 °C between (i) two hydrogen molecules and (ii) two nitrogen molecules, if each pair is separated by 0.3 nm. Explain fully and clearly your reasoning and any assumptions you make in your answer. State the source of the values of any...

Do they unbind somehow? Or are they somehow "eaten" by the receptor, so the more you taste of something, the less of it gets through? I'm only a Wikipedia/Youtube student so my knowledge has weird gaps all over the place. Got thinking about this by noticing an interesting taste that some...

Avogadro's Law states that 'equal volumes of gases at the same temperature and pressure contain the same number of molecules' or moles of gas. My question is ,will it be correct if we reverse the law, I mean if gases of equal moles at the same temperature and pressure will have equal volumes,is...

I'm watching a Leonard Susskind video about the Higgs Boson where he gives an example of how an electric field can change the mass of a water molecule. If you put a water molecule between two capacitor plates (so the electric field is uniform and the field lines are parallel), it will tend to...

I just began reading Feynman lectures and it turns out that during evaporation, water molecules that move faster than average (higher temp) break away from the attraction of their neighbors leaving behind molecules that move slower than average (lower temp) and result in a cooler liquid. When a...

Suppose the molecules of an ideal gas move with a speed comparable to the speed of light. I am trying to adapt the kinetic theory to express the pressure of the gas in terms of m and the relativistic energy, but each time I try to derive the expression, I get: P = (1/3)(N/V)(v/c)√(E2 - m2c2)...

Hello ! When we say that we use a 6-31G for a molecule (ex: N2), it is this number of gaussian (6+3+1) for both of the atoms or for each atom ? Thank you

I read an article about creating molecules from photon, and this part- As the photons enter the cloud of cold atoms, Lukin said, its energy excites atoms along its path, causing the photon to slow dramatically. As the photon moves through the cloud, that energy is handed off from atom to atom...

Homework Statement Hi all, There is a question from the course book: Homework Equations S=k_B ln W The Attempt at a Solution My solution: So first of all, for each molecule, there are 2 motions: translational and rotational. For rotational I get: W_1 =\Omega \left ( \theta \right ) For...

I want to design a system of some kind that will photodissociate isolated diatomic molecules. I began by looking at Einstein's treatment of absorption and emission rates, molecular orbital geometry, the Morse potential and various other topics. I'm fairly well versed in quantum and E&M (full...

I am working on a project, however I am having trouble finding the right material for it to work. I am looking for a nano-material or any molecule that will emit a radio frequency when subjected to a voltage or a current at around 37 degrees Celsius. I would really appreciate it if someone could...

Homework Statement I know that temperature is a measure of the kinetic energy of gas molecules. at a given temperature different gases have the same average kinetic energy. But in solids and liquids there is also potential energy between the close atoms/molecules. how do i know that temperature...

Hi, so I'm a first year neuroscience student at Carelton University in Canada. I had a little bit of a "revelation" with this topic recently after I understood it a bit better and I think this is really interesting. (If I understand it correctly!) We're learning about Kekule structures...

Homework Statement 1. A student investigated several esters, and made octyl acetate, an ester with the fragrance of oranges. The student used the acid derivative, acetyl chloride (as you saw decanedioyl dichloride used to make 6,10 nylon) and 1-octanol. Using the following information...

Homework Statement Part A: Calculate how many mocules per cubic metre in air at 27°C and at a pressure of 1.1 atm (1atm is 1.01 x 10^5) Part B: What is mass in grams of 2.4m^3 of this air. Assume that 75% of the air is N2 (with molar mass of 28 g/mol) and 25% O2 (with molar mass of 32 g/mol)...

For diatomic molecule, why is the vibrational degree of freedom equal to two at high temperature? Why not just one? Thank you very much.

I'm stumped as to how many optic branches (modes) are present if there are X number of molecules in a unit cell and Y number of atoms in each molecule. I know that each individual atom has 3 degrees of freedom and more generally in a single unit cell, there are 3 acoustic branches (modes) and...

I took chemistry a couple years ago but never got a satisfactory answer as to why covalent bonds hold molecules together. I understand that they share their outermost electrons, but why would that keep them together? Do the electrons pull against each other or something?

Hey, guys, I have just watced a fantastic animation of the microscopic process of sound wave traveling, in which model was described as many balls connected by springs. But the problem is what we learned in thermodynamics chapter is that there is no bonds between molecules in gas, then how...

I solved the problem myself immediately before anyone replied.

1. Suppose DNA molecules of a Streptococcus bacterium contain a radioactive isotope N^{15}, if this bacterium is then put in an environment containing only N^{14} and after 5 generations (DNA duplication), how many N^{15} DNA molecules remain ? Homework Equations 3. after 5...

As I understand, when an electric field is applied to an atom then the nucleus and electron cloud will be shifted out of balance giving rise to an electric dipole moment. Some molecules have permanent dipole moments though, e.g. Hydrogen Chloride, ". . . when a hydrogen chloride molecule is...

Hello there. I did research on some of Schrodinger work. My question is the transfer of Energy between the Atoms and Molecule. Schrodinger made an analogy with the Cat/Atom Scenario but the real particle in question is the NH2 Mole & H-Atoms with ghost energy being observed. The reason I read...

(1s,4s)-4-(tert-butyl)-1-methylcyclohexan-1-ol (1r,4r)-4-(tert-butyl)-1-methylcyclohexan-1-ol These are the two results given by the solution's manual textbook to this question: Keeping in mind that carbocations have a trigonal planar structure, (a) write a structure for the carbocation...

Hello, Is there anywhere a reference to get an idea, why wool fat consists of over 200 different molecules? Is there some sort of a general law or ruling, like the Darwin's evolution, that nature produces nothing more and nothing less as what is required for the propose? If so, how is...

I read that essential oils can go through the skin. I am told that there are more water molecules in just 10 drops of water than stars in the whole universe, so if they are so tiny, why don't they go through the skin membrane pores, which are perfectly visible under an optical microscope? You...

How to determine the bond angle based on the formula of molecules?

One of the first things about QM we were taught in my undergraduate physics program is the deBroglie relation: λ = h/p Now, it makes sense that that this might hold for all elementary particles, especially since the evidence generally seems to suggest that the commonly observed forms of...

When water is vigorously shaken the kinetic energy and, hence, the motion of the molecules increase. Which particular forms of energy do increase : the translational energy (is this the energy associated with the collision and the chaotic random motion of the water molecules ?) or also the...

Homework Statement How many water molecule in CuSO4.5H2O attached only by coordinate bond? The Attempt at a Solution Copper exists in the form of Cu2+. So, it has one vacant d-orbital. The answer should then be 1. But it's 2 :(

Are species such as sulfuric acid and phosphoric acid better represented as charge-separated species rather than as species with no formal charge on any of the constituent atoms? Also are the central atoms of trigonal bipyramidal molecules (e.g. phosphorous) hybridized as sp3d2 or do such...

Homework Statement Part(a): Find rate of incidence of gas molecules. Part(b): Find v1 and v2. Part (c): Find mean free path for faster molecules. Part (d): Find mean free path of 10m/s molecules. Homework Equations The Attempt at a Solution Part (a) Letting ##\phi## be flux, and ##\Delta...

The number of molecules per cubic metre of air at standard temperature and pressure is about 2.7X10^25 / m^3 . What is the average separation of these molecules? I know the number of molecules is derived from the equation pv=nRT.But what does average separation of molecules mean and how do i...

It is taught that the classical treatment of the diatomic atom would give a heat capacity of $7/2$ due to 7 degrees of freedom, (three translational momentum, two rotational momentum, on vibration momentum and on vibration position). This is based on the Hamiltonian looking like: $$ H =...

Homework Statement What is the number density, N/V, of gas molecules in the closed vessel in the previous problem? (Previous problem: A closed vessel contains an ideal gas at an absolute pressure of 1.5 atm and a termperature of 42 degrees celsius. To what final temperature (in °C) must the...

I'm trying to understand how to draw MO diagram for molecules such as CO, HF, and NO. I am finding so much conflicting information on how to order the σ and pi boxes in the diagram. Now, I know that the more electronegative atom's orbitals are going to be lower in energy than the less...

The bond enthalpies for these bonds are: C-C 347 kJ/mol C-N 276 kJ/mol C-O 351 kJ/mol Why is carbon-nitrogen bond enthalpy lower? What factor makes that? And also the halogens bond enthalpies: F-F 157 kJ/mol Cl-Cl 243 kJ/mol Br-Br 193 kJ/mol I-I 151 kJ/mol Why has fluorine lower enthalpy? I...

Homework Statement https://ia701205.us.archive.org/11/items/Mechanics_541/LandauLifshitz-Mechanics.pdf Page 72 of the book itself, but Page 81 of the PDF. Problem 1. Homework Equations See Section 24 of the book. The Attempt at a Solution So far I have completed and...

What happens when a gas molecule collides with a liquid molecule at the microscopic level ?