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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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Cyclic Voltammetry for a Capacitor - Positive Current, Potential is decreasing?

In the boxed red region, why is the potential decreasing when the current is still positive? To my understanding, when the current is still positive (i.e. not changing direction), the capacitor will ...
photon's user avatar
  • 79
0 votes
1 answer
51 views

Based on RPDs, how to tell which orbital ($2s$ vs $2p$ or $4s$ vs $3d$) is more stable ? How reliable is the "less shielded" argument? [duplicate]

Professor (from MIT $5.111$ class) argues that $E_{2s} < E_{2p}$ by just saying that, due to the little bump of $2s$ (on the left of its RPD graph), $2s$ is less shielded and, hence, has lower ...
niobium's user avatar
  • 239
1 vote
1 answer
62 views

Theoretical justification for the definition of standard enthalpy of reaction

I've been reading the book Chemistry: Core Concepts by Allan Blackman, Daniel Southam, Gwendolyn Lawrie, Natalie Williamson, Christopher Thompson and Adam Bridgeman. They give the following definition ...
russell.price's user avatar
0 votes
0 answers
43 views

Do high-energy conformers allow for more flexibility in ligand binding?

After reading, "High Energy Conformer - Why is it the most stable?" which is at risk of being closed due to lack of detail, I'm curious whether my thoughts on reasons for selecting a high-...
Melanie Shebel's user avatar
2 votes
0 answers
52 views

Why is the translational motion left out of the energy eigenvalue in the hydrogen atom?

When solving the hydrogen atom, since we have two particles, the wave function has the form $\psi(\mathbf{q}_1,\mathbf{q}_2)$. Generally, textbooks proceed to demonstrate that an interacting two-...
Metal Storm's user avatar
  • 3,556
-2 votes
1 answer
44 views

Why does increased reaction temperature favor endothermic but not exothermic reactions? [closed]

Why does increasing the reaction temperature favor the endothermic but not exothermic reaction? Increasing the reaction temperature will increase the molecular movement no matter reactants for ...
Li Cheuk Hin's user avatar
1 vote
0 answers
80 views

High Energy Conformer - Why is it the most stable? [closed]

I'm doing docking studies. Upon preparing my ligands, I've conducted conformational analysis to them using RDKit and plot their respective potential energies. I'm just confuse why my thesis advisers ...
Carbon Nanotubes's user avatar
0 votes
2 answers
104 views

Finding the point where reaction switches from endothermic to exothermic

One mole of monoatomic gas undergoes a linear process A to B shown in P-V diagram. Volume of gas from where process turn from an endothermic to an exothermic is? I tried to calculate the point where ...
JackSparrow's user avatar
4 votes
1 answer
99 views

Gibbs energy of an imperfect crystal

Our materials professor likes to do Kahoot quizzes and I am confused about why the following statement is true: A defect in a crystal gives it higher energy. I know that an imperfect crystal has a ...
Christian's user avatar
  • 211
2 votes
1 answer
53 views

Frequency to induce nitrogen inversion

I would like to know how to compute the frequency at which nitrogen inversion happens in ammonia gas at STP. The activation energy for such process is 24.2 kJ/mol, therefore I thought that it is ...
crisecon's user avatar
-5 votes
1 answer
70 views

Why are internal energy and work mentioned in a question about exothermic or endothermic systems? [closed]

This is a question from my chemistry homework. Note the explanation below. A 100.0-g bar of gold is heated from 25°C to 50°C during which it absorbs 322 J of heat. The volume of the gold bar remains ...
Shay's user avatar
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0 votes
1 answer
86 views

Energy released by aluminum reactions

I heard that aluminum reacts violently when exposed to hydrochloric acid. I was wondering how much energy is released by this reaction. Preferably in MJ/kg or MJ/l. Assuming the reaction needs 2 moles ...
Nitrogen-8's user avatar
0 votes
0 answers
55 views

Why is ammonia more energy dense than ammonium nitrate?

On wikipedia's extended reference table they state that ammonium nitrate has an energy density of 1.4Mj/kg or 2.5MJ/l. Ammonia was said to have an energy density of 16.9MJ/kg or 11.5MJ/l. This seems ...
Nitrogen-8's user avatar
-2 votes
1 answer
53 views

Heating a Single Water Molecule [closed]

From my understanding, phase changes break/form bonds between molecules of the same substance. Assuming this is in a vessel at 1atm of inert gas, if I have one molecule of water with no bonds to other ...
Camel Camel's user avatar
0 votes
0 answers
44 views

Why does enthalpy change and not internal energy help in determination of spontaneity?

Spontaneity of a process is measured by Gibbs Free Energy $$\Delta G= \Delta H-T\Delta S$$ $$\Delta H=\Delta U+\Delta (PV)$$ Is there an intuitive explanation for why Gibb's energy depends upon ...
Portuguese Man Of War's user avatar
1 vote
0 answers
59 views

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
1 vote
2 answers
88 views

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 ...
Nefeli 's user avatar
  • 141
1 vote
0 answers
42 views

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
0 votes
1 answer
136 views

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
0 votes
1 answer
109 views

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
  • 233
0 votes
1 answer
90 views

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
  • 103
1 vote
3 answers
191 views

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
0 votes
2 answers
246 views

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{...
user21820's user avatar
  • 238
0 votes
0 answers
63 views

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
  • 362
0 votes
4 answers
336 views

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
  • 2,307
-2 votes
1 answer
48 views

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
4 votes
0 answers
40 views

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/...
dlight's user avatar
  • 337
1 vote
1 answer
143 views

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
  • 11
-1 votes
1 answer
54 views

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
-1 votes
1 answer
50 views

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
0 answers
75 views

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
-3 votes
1 answer
83 views

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
  • 1
0 votes
1 answer
100 views

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
4 votes
1 answer
165 views

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
-4 votes
1 answer
28 views

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
  • 412
-2 votes
2 answers
200 views

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
-4 votes
2 answers
100 views

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
0 votes
1 answer
464 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
  • 11
1 vote
3 answers
145 views

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
-4 votes
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
-3 votes
1 answer
57 views

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
  • 1,065
-1 votes
1 answer
64 views

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
  • 119
-1 votes
1 answer
72 views

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
446 views

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
-1 votes
2 answers
240 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
  • 327
-2 votes
1 answer
84 views

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
  • 269
9 votes
3 answers
1k views

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
209 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
0 votes
1 answer
108 views

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
110 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

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