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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Can 1/time be a good proxy for k in the Arrhenius' equation?

I am trying to do the iodine clock reaction with different temperatures. I will be using curcumin as a reducing agent instead of vitamin c or thiosulfate. If $1/t$ can be taken, I could take natural ...
Yogi's user avatar
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Work from a spontaneous endothermic reaction?

Some reactions are spontaneous ($\Delta_\mathrm{r}G < 0$) although they are endothermic ($\Delta_\mathrm{r}H > 0$), e.g. the plastic packs that once cracked they get cold. I saw that it is often ...
Olfaction's user avatar
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raising the temperature for exothermic versus endothermic reaction

My textbook says "an increase in temperature causes a far greater increase in successful collisions for an endothermic reaction compared to an exothermic reaction" Why is this?
moon river's user avatar
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Is light energy defined as work in thermodynamics?

Is Light/Radiant Energy considered Kinetic Energy or Potential Energy? I have started studying Thermodynamics, and the concept of internal energy was introduced, and defined as the sum of kinetic and ...
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When bonds are formed, where does the energy released come from? [duplicate]

Bond formation is always exothermic, meaning it releases energy, but where exactly does this energy really originate from? From my understanding the product has less energy than the lone atoms, hence ...
Fake's user avatar
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Increasing energy density for flow batteries with water based electrolyte?

Given a flow battery with a water based electrolyte, would it be possible to increase the energy density of battery by precipitating the redox active species from the anolyte and catholyte solutions? ...
Lance Collins's user avatar
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Mg2+ ion formation [duplicate]

Why does Mg not form a Mg+1 ion, even though its second ionization energy is much higher than the first ionization energy? (I know that an ion should resemble the noble gas closest to the element from ...
Saar Segen's user avatar
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What is the difference between standard Gibbs energy and Gibbs energy of formation?

Good day guys, I am reading a book on electrochemical engineering, I came across some definitions of Gibbs energy and I am a bit confused as the book does not go into a lot of detail. The book first ...
RMS's user avatar
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How to compute solvent reorganization energy in Marcus' non-equilibrium approach?

I try to solve the following equations for some system solvated in the water. The goal is to obtain value in kcal/mol. Unfortunately, I cannot reach the desired output. May someone help me? The ...
farmaceut's user avatar
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3 answers
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How can I model the melting of ice as a function of time?

How much time it will take for a ball of ice at 0 °C and radius 3 cm submerged in 1 l of water at 100 °C to completely melt? (Assume the ice melts completely uniformly and treat it as a shrinking ...
DoTheMath's user avatar
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Ozone formation

I have read about the formation of natural atmospheric ozone on Wikipedia, where it is claiming that the ozone creation step requires an extra molecule in order to conserve momentum and energy: $$\ce{...
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Units of Activation Energy

Consider the reaction $$\ce{aA + bB -> cC + dD}$$ whose reactants are given by A and B and the products are C and D. Say the activation energy of this reaction is some $x$ joules/mole, But moles of ...
Shashaank's user avatar
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Do conformations arise from vibrations?

I was wondering how a molecule transforms from one conformation to another. Surely, since the conformations are separated by a potential barrier, some activation energy must be required. The energies ...
ananta's user avatar
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Where does the ionisation energy for a reaction to take place comes from? [closed]

Can anyone tell me exactly what happens during a chemical reaction in terms of ionisation energy? I know that during a reaction there is an exchange of electrons (except for those where electrons are ...
Zane Stockton's user avatar
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Can you give an example of an electrolytic process that has high Faraday efficiency but low energy effiency

I want a nice example to help illustrate the conceptual difference between these terms to a biologist. I found this figure which might be helpful.https://www.researchgate.net/publication/...
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What are the key differences between combustion of starch and sugar

I performed an energy content experiment the other day using a rudimentary bomb calorimeter. The experiment was comparing for the energy release of a sugary food (Arnott's Tiny Teddies) to the energy ...
Thomas's user avatar
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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 ...
Jorge Bonifaz's user avatar
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1 answer
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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 ...
Elaine Gerrard's user avatar
2 votes
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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 ...
big_yoshi's user avatar
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1 answer
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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 ...
aiman's user avatar
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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 ...
Govind Prajapat's user avatar
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1 answer
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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{...
Neal Conroy's user avatar
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1 answer
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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. ...
Srijan's user avatar
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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 ...
Govind Prajapat's user avatar
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2 answers
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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 ...
Anirudh Sharan's user avatar
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1 answer
341 views

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 = "...
ait2001's user avatar
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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 ...
Charles Dickens's user avatar
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1 answer
69 views

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 ...
Authentic Melody's user avatar
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1 answer
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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 ...
user2617804's user avatar
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1 answer
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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 ...
Chemistry's user avatar
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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: $$H=U+PV$$ ...
Dennyc39's user avatar
3 votes
1 answer
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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 ...
Ca Sagan's user avatar
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2 answers
209 views

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 ...
Volpina's user avatar
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1 answer
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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}\...
Mailbox's user avatar
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9 votes
3 answers
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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 ...
Mikayla Eckel Cifrese's user avatar
5 votes
1 answer
198 views

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 ...
matt_black's user avatar
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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 ...
Arsenal Creation's user avatar
-1 votes
1 answer
103 views

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 ...
Belal Bahaa's user avatar
2 votes
0 answers
87 views

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: $$e^{-E_A/RT}$$...
FShrike's user avatar
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3 votes
2 answers
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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+...
Audrix's user avatar
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0 answers
280 views

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....
QMLSorbonne's user avatar
1 vote
2 answers
69 views

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 $...
Belal Bahaa's user avatar
-3 votes
3 answers
724 views

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 ...
Paul Jurczak's user avatar
3 votes
3 answers
400 views

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 ...
Jono94's user avatar
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2 answers
109 views

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 ...
Bohan Xu's user avatar
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2 votes
0 answers
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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(...
JAClarke's user avatar
0 votes
2 answers
775 views

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 ...
James Chadwick's user avatar
1 vote
0 answers
55 views

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) -> ...
itisyeetimetoday's user avatar
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1 answer
111 views

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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