Questions tagged [energy]
For questions relating to the energy required for or produced by reactions, including questions of endothermicity/exothermicity, bond enthalpy, etc.
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energy released per second due to the radioactive decay [closed]
What is the magnitude of the energy released per second due to the radioactive decay of a 20-gram sample of strontium-90 isotope, given a decay energy of -0.546 MeV?
the energy I mean is the total ...
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Glycolysis energy [closed]
I understand that chemical reactions require Activation energy for building molecules, and these reactions typically have a positive net energy gain, And breaking chemical bonds require energy, ...
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Conformational analysis [closed]
In organic chemistry, much emphasis is given to the study of the conformers of alkanes and the broader topic of conformational analysis. Can you elucidate why the spatial arrangements and rotations ...
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Electron energy shells/ levels
Essentially, I am told electron shell closest to the nucleus is the lowest energy level and subsequent shells have higher energy (I.e. those further from the nucleus).
But..... electrons in the ...
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Which methoxy- and nitro-substituted azulene has the lower ground state energy?
My contention is that the first azulene structure, with the nitro group on the aromatic cyclopentene ring has a lower ground state energy, as the negative charge can not only resonate into the nitro ...
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calculation of enthalpy change
So for for the calculation of $\Delta{H}$,we have two formulaes in our book:
$\Delta{H}=E_{2}-E_{1}$
where $E_{2},E_{1}$ are the internal energies of the product and reactants respectively.
Now this ...
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Kinetic energy change in reaction
If we consider a reaction occurring at constant pressure and temperature , we know that enthalpy represent the net heat released or absorbed by the system and internal energy accounts for both heat ...
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What is the probability the bonds broken with sunlight reforming back?
The maximum wavelength $\lambda$ capable of breaking a chemical bond can be estimated as $\lambda = hc/E.$
UV-A $(\pu{380 nm})$ can break bonds with the energy up to $\pu{315 kJ mol^-1},$ UV-B $(\pu{...
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Why is there a point of orbits along with quantization in case of energy gaps?
As per my textbook and online sources. The definition of Energy bands I have found is this:
A) Energy levels:
( In a simplified view of an electronic structure of a single atom or isolated molecule.
...
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Thermodynamics potential and differences between them
There are 5 most common thermodynamics potential -
But we will discuss about only three of them -
Internal energy (∆U)
Enthalpy(∆H)
Gibbs free energy (∆G)
As Gibbs free energy is also a ...
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Resonance energy of organic compounds [closed]
I was solving a problem in organic chemistry, where I had to find the resonance energy of a compound with some information which was given in the question itself. Basically, what I had to do was, to ...
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Gibbs free energy versus reaction progress plots
I am trying to make sense of these two graphs. They appear to have similar axes, yet display different curves.
Please let me know if this understanding is correct:
In the top image (x-axis = "...
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Comparing Succesive Ionisation Energies
I am trying to understand successive ionisation energies. In particular, an explanation for why the second ionisation energy is greater than the first ionisation energy. I'm looking for a clear and ...
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What factors determine the distribution of chemical energy between work and heat in a chemical reaction? [closed]
In the context of a chemical reaction, what factors determine the allocation of chemical energy between performing pressure–volume work and generating heat? Are there any key parameters or variables ...
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Is there any evidence to show that chemistry does not represent a mass to energy exchange?
As per Einstein relationship, $E=mc^2$ or its more correct form $E=\sqrt{(mc^2)^2 + (pc)^2}$. The mass loss would be extremely tiny given how little energy is exchanged in chemical reactions. But is ...
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when would copper material have free electrons [closed]
If you imagine a wire of copper(note that I am not talking about electricity at all). Just only a wire of copper or copper metal or whatever full of copper atoms.
We know that each copper atom has 1 ...
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Understanding the definition of enthalpy [duplicate]
My chemistry text describes Internal Energy (U) of a substance as the sum of all categories of energy, i.e., Kinetic (temperature), potential, bonding, etc.
Then, Enthalpy is defined as:
$$H=U+PV$$
...
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Enthalpy change of neutralisation?
Consider this problem.
The enthalpy of neutralisation is defined as the enthalpy change when one mole of water is formed through the react of an acid and base at standard conditions. As the ...
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Virial theorem confusion
Virial theorem says that $E_{t} = -\frac{E_{P}}{2}$ however this says that lets say for 2 gas molecules(Ne) the kinetic energy due to temperature a molecule of $Ne$ at 0K will have the same energy ...
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What does the constant mean in this equation for the energy levels of an atom?
My textbook, Silberberg & Amateis, Chemistry: The Molecular Nature of Matter and Change (9th ed.), gives the following equation for calculating the energy level of an atom:
$$E = \pu{-2.18E-18 J}\...
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How does an electrons's wave function change when it moves between energy levels?
I'm taking a class on QM and we're simulating the wave function of an electron in a box at the lowest energy level and I'm supposed to change the simulation to show the wave function for the next ...
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What would the maximum energy density of a power source based on carbon-14
Various ways of generating electricity from small radioactive power sources have been long known.
The Voyager space probes launched in the 1970s use thermoelectric generation from plutonium sources to ...
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How can we say that p in ΔU= q_p-pΔV and p in ΔH=ΔU+pΔV are equal? About the derivation of ΔH=q_p
I was studying about thermodynamics and everything was fine until I studied about enthalpy $H$. The first thing I wanna know is what is $p$ in eq. $H=U+pV$. Is it internal pressure or external ...
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How can I measure the energy contained within water vapor?
Let’s say I have a kilogram of water vapor at $\pu{423 K}$. Can I directly measure the energy, contained as heat, within the vapor? All the laws I know depend on knowing the changes that happened that ...
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Is the proportion of molecules with sufficient energy to react *really* equal to $e^{-E_A/RT}$?
In A-level chemistry class today I was just told the following:
For a reaction with activation energy $E_A$, the proportion of reactant molecules with kinetic energy $\ge E_A$ is: $$e^{-E_A/RT}$$...
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Why does a symmetric stretch mode not have an imaginary frequency?
Currently studying potential energy systems and our professor asked a question at the end of a lecture and I can't wrap my head around it.
He said, "Picture a 2D PES for the simple reaction of H+...
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Energy of a molecule using MOs diagram (case of CH4)
I'm trying to find the ground state energy of CH4 in order to compare it with simulations I made. I came across this diagram of energy (not sure it gives the true energies though, if you could confirm....
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Should I give an endothermic reaction the exact energy it needs to occur or can I give it in parts?
I know this might be a silly question, but should I sustain the exact energy or more for the enthalpy of endothermic reaction to occur or can I give it in parts?
Let's say a certain reaction requires $...
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What form of energy is produced by 2H2 + O2 -> 2H2O reaction? [closed]
I'm curious about are the details of exothermic nature of 2H2 + O2 -> 2H2O reaction. The explanations I've seen just use a term "energy release" without specifying what type of energy it ...
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Effect of coal and natural gas burning on particulate matter pollution
I sometimes hear people talking about how we should replace coal burning plants with natural gas ones, to alleviate the case of particulate matter pollution. What exactly is the difference between ...
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Is there an intuitive answer why burning is very exothermic? [closed]
Water and carbon dioxide are much lower in energy than hydrocarbon and oxygen. Is there an intuitive answer for this? Is this because atom arrangements that have more polar bonds tend to be lower in ...
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Why is the imine (C=N) bond so weak?
Nitrogen is similar to carbon in terms of electronegativity and size. MO theory suggests that the more electronegative N would result in a lowering of the of the π-bonding energy, E(πCN), below the E(...
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Why does temperature remain constant during phase changes?
In a phase change the temperature remains constant but I can't understand why. The answers I have read state that during phase changes energy is only used to break bonds between molecules rather than ...
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Reproducing Hydrogen Molecule Hamiltonian in OpenFermion
I am learning quantum chemistry at the moment and I'm trying to understand the Hamiltonian generated by the OpenFermion package. I'm now stuck at understanding how openfermion calculates the ...
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Enthalpy and Bond Energy Sign Convention
I read that a negative enthalpy of formation means an exothermic reaction. Does that mean this reaction is true? The enthalpy of formation for $\ce{H_2O}$ is -285.8 kJ/mol.
$$\ce{2H2(g) + O2(g) -> ...
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Variation in the energy of the $\ce{\sigma_{2pz}}$ orbital
Is there a specific reason why the energy of the $\ce{\sigma_{2pz}}$ orbital varies relative to the $\ce{\pi_{2px}}$ and $\ce{\pi_{2py}}$ orbitals, depending on the atomic number of the atom?
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What role does atomic radius play in the strength of a covalent bond?
How exactly do atomic radii influence the strength of a covalent bond? For instance, if I had a carbon atom covalently bonding to a fictitious nonmetal atom $\ce{X}$ and another nonmetal atom $\ce{Y}$ ...
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How to obtain reliable ligand binding energy in QM manner?
I wish to compute the binding energy of the ligand to the known cavity of the receptor.
My idea was to:
Perform docking to the recognized binding site using AutoDock Vina
Export bound ligands and ...
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Is there any process that converts water into hydrogen and oxygen by using light and a catalyst?
Can water be converted into hydrogen and oxygen using sunlight and a specific catalyst? I can imagine a electrolysis reaction using a catalyst that uses light to release electrons. The goal is to find ...
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Why would a metal form an ionic compound with a nonmetal from a lower period?
Take sodium iodide for example. I understand both elements can obtain a full outer shell via the electron transfer. But doesn't the electron move from a lower-energy orbital ($3s$ in sodium) to a ...
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How does the density of states (DoS) of Jellium scale with the number of electrons for constant electronic density?
I'm trying to understand the behavior of the density of states when we grow a system, such as $$C_n H_{2n+2}.$$ Since this is probably too complicated, I am interested in jellium first. Is there any ...
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How are photons converted into thermal energy?
I know when light strikes an object it excites electrons into higher energy states. I know thermal energy is basically just a lot of atomic and molecular kinetic energy. Does the excitation of the ...
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Relation between activation and threshold energies
Activation energy $E_\mathrm{a}$ and threshold energy $E_0$ appear to be equivalent quantities:
In particle physics, the threshold energy for production of a particle is the minimum kinetic energy a ...
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What is the energy difference between inner subshells?
For exemple, in silver the energy difference between the 4d 5s subshells is ≈ 4 eV (in the ultraviolet region, that's why it has no color, etc.), but what is the energy difference between some of its ...
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Definition of activation energy
There seems to be contradictions in the definitions of activation energy ($E_a$) stated by different sources. I found two such popular definitions. Before that, I state my understanding of how an ...
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Why ionization energy of Thallium is higher than that of Indium?
I just normally calculated the effective nuclear charge (Zeff) for thallium and Indium from Slater's law, and I found it same for both! That is 5.(If you want calculation for answering or correcting ...
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Where does the energy in coal bonds come from?
I have been told that when the plants intake carbon dioxide they break carbon and oxygen apart and the carbon is utilised in making the plant's body. This process is driven by the sun's energy so when ...
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What makes a compound high or low energy and why does that relate to reactivity? [closed]
After reading about thermodynamic stability, it now makes sense to me how the enthalpy of a reaction relates to the thermodynamic stability of a compound.
However, when looking for a clear way to ...
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Spontaneity criterion for phase transformations and chemical reactions [closed]
Why is the Gibbs free energy (G) considered a spontaneity criterion for phase transformations and chemical reactions? Why are other thermodynamic parameters such as enthalpy (H), entropy (S), and ...
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What scientific and technical challenges prohibit the industrial use of the Sabatier reaction?
It seems that the Sabatier reaction solves the biggest problem of climate change — it does create clean gas and hydrogen fuel from the captured carbon dioxide and water (from melting ice).
$$\ce{CO2 + ...
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