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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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 ...
-5 votes
1 answer
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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 ...
2 votes
1 answer
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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 ...
2 votes
2 answers
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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 ...
7 votes
6 answers
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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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1 answer
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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 ...
-1 votes
2 answers
49 views

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 ...
1 vote
1 answer
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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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Why does a double-bonded nitrogen molecule have more than twice the bond (dissociation) energy of a singly-bonded one?

If the first bond between atoms is (usually) stronger than the second one, and the second one, in turn, a bit stronger than the third, how does a doubly-bonded nitrogen molecule have more than twice ...
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1 answer
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What does it mean when we say an atom has infinite energy levels/shells? [closed]

My chemistry teacher told that an atom has infinite energy shells according to Bohr model , where electron reside according to its angular momentum and energy. But in lower classes/ grades I have ...
3 votes
1 answer
131 views

Why is rapid expansion/compression reversible?

I am looking over the Otto Cycle on this MIT website and it says at one point "the processes from 1 to 2 and from 3 to 4 are isentropic" in reference to the expansion and compression of the ...
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What is the bond energy of Si-O?

I was taught that deprotection of silyl ethers (and more generally the cleavage of silicon-oxygen bond) could be done with fluoride ions, this reaction being driven by the fact that the Si-F bond is ...
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1 vote
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Calculating Band Gap Energy When Absorption Spectra Shifts with Concentration?

I am not a chemist. However, from some experimental work I have been doing, I have found that the intensity of the spectrum changes with dilution, this makes sense. However, when calculating the band ...
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0 answers
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Data for Madelung Constants

Where can I find data for the Madelung constants for various ionic compounds? Specifically, I am looking at silicon tetrachloride, yttrium (III) chloride, zirconium (IV) oxynitrate hydrate, niobium (V)...
4 votes
1 answer
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Can a spontaneous reaction have zero or negative activation energy?

Is it possible for a certain spontaneous reaction to have zero or negative activation energy? My high school teacher explains that it shouldn't be possible since it breaks the Arrhenius equation, ...
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4 votes
3 answers
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Where does the energy required to initially begin the reaction of iron and oxygen come from?

When iron is left outside, over time it reacts with oxygen to form iron oxide or rust. But how does the oxygen react with iron, isn't iron held together by strong metallic bonds? Where does this ...
1 vote
0 answers
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Resource estimate for ab initio calculation [closed]

I have recently come across this very intriguing paper “The Fundamental Vibration of Molecular Hydrogen”. I have asked the authors the following naïve questions directly via email? What was the ...
0 votes
2 answers
99 views

Is it possible to modify how energy is released in the combustion of a fuel like methane? [closed]

From what I understand (please correct me if I'm wrong), combustion is an exothermic oxidation reaction where, for example, a fuel like methane is combined with oxygen, i.e. CH4 + 2O2 → CO2 + 2H2O. My ...
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1 answer
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Melting and Freezing [closed]

Ok so I needed some help understanding one concept, for eg:- we are in an isolated room that has a room temperature of 0 degrees Celsius. And I bring in some water in the room, so eventually it will ...
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4 votes
1 answer
108 views

How to compute the electronic energy reported by Gaussian from the AlphaOrbitalEnergies?

I followed the instructions on Wolfram Language & System Documentation Center — FCHK (.fchk) to analyze the *.fchk file. I ran an energy calculation with ...
-3 votes
1 answer
101 views

why does sodium chloride in water dissolve/precipitate with little heat, or indeed, at all? [closed]

Sodium and chlorine presumably react together strongly, which is why the solid product is stable and takes a lot of energy to break the bonds formed, and to melt. According to the Wikipedia, melting ...
-2 votes
1 answer
79 views

Why does a carbon double bond "break readily" but this is not so for other elements (nitrogen double and triple bonds are stronger)? [duplicate]

A level chemistry student here, fairly basic question. We always learnt (from GCSE bond enthalpies) that "Bigger bonds are stronger", so to speak; my teacher often quoted $\ce{N#N}$ as very ...
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2 answers
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Impact of temperature on an Energy profile diagram

What happens to the energy profile diagram if you increase the temperature of the system? From my understanding, I think the whole diagram would shift upwards, as the reactants and products will both ...
3 votes
0 answers
79 views

State-of-the-art results on molecular vibronic energy calculation

Could someone kindly point me to the latest records in scale, accuracy, or timescale for molecular vibronic energy calculation? I tried to start with Google Scholar: https://scholar.google.com/scholar?...
0 votes
0 answers
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How to calculate the temperature of a mix?

I'm trying to solve a problem but there is something im not quite getting. It says, if we mix 84.2 mL liquid water at a 15°C and 50 mL of 100% sulfuric acid at 25°C, What is the maximum temperature ...
-2 votes
1 answer
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How to calculate ionization energy of an atom provided energy of the electron at ground state? [closed]

It is given that in ground state the energy of electron in hydrogen atom is $-2.18\times10^{-18}\mathrm{J}$. I'm required to calculate the Ionization Energy in kJ/mol Question for reference: At ...
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Using bond energies to calculate the released energy of a neutralization reaction

I am trying to make a simulation of a neutralization reaction that simulates the change in enthalpy as the reaction progresses. The strategy I have decided to go with is using the energy of the ...
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2 votes
1 answer
131 views

Relation between concentration and activation energy

Will increasing the concentration of the reactants in a chemical reaction increase the proportion of molecules with an energy greater than the activation energy $E_\mathrm{a}$? It seems to me that the ...
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Energy change of isentropic expansion of ideal gas

I'm trying to get a better grasp on dealing with different processes thermodynamic, and this one is giving me trouble. The differential of energy is given by $$dU= \delta Q + \delta W~.$$ I'm ...
0 votes
1 answer
386 views

How do I calculate the maximum temperature of an exothermic NaOH reaction in water?

As the title suggests, let's say I want to make a 1 L 14M NaOH solution. For this I'd need: (14 mol/ L) x 1 L x (39.99 g / mol ) = 559.86 g NaOH(s) {solute} ~1 L H2O (approx) {solvent} The ...
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2 votes
0 answers
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How to apply the Geiger–Nuttall rule to find half-life?

I'm having trouble understanding the Geiger–Nuttall rule for α-particle decay. From the textbook I'm using, the rule is defined as $$ \log(t_{1/2}) = A + \frac{B}{\sqrt{Q_\alpha}}, $$ where the ...
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1 answer
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Where do electrons jump to when they jump to next shell in emission spectrum? Why are there no emission lines for jumps btwn orbitals, same shell?

In the emission spectrum, do electrons that jump up to the next shell go to any orbital in that shell? Or if the electron is originally in say the p orbital, does it jump to the next p orbital in the ...
1 vote
1 answer
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Calculating Enthalpy of formation versus Calculating Enthalpy of a reaction not occurring at standard conditions

My understanding of Hess's law and its use in determining the change of enthalpy of a reaction has been challenged recently. Up until recently, I thought that the only way to calculate a chemical ...
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2 votes
0 answers
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Would a PNG geyser work on biogas?

I am trying to understand if a water heater designed to run on piped natural gas (PNG) could be powered by biogas without any modifications. Typically, these geysers have a battery-powered ignition ...
6 votes
1 answer
1k views

Where does the energy from combustion come from?

I am aware that combustion reactions are exothermic. The energy stored in the chemical bonds of the products is less than the energy stored in the chemical bonds of the reactants. The difference in ...
1 vote
0 answers
40 views

Gibbs energy of electron transfer

the reaction Gibbs energy of a cell: $\Delta_rG^o=-nFE^o$ and the Gibbs energy of photoinduced electron transfer: $\Delta_{ET}G^o=N_A\{e[E^o(D^{+.}/D)-E^o(A/A^{-.})]+\omega(D^{+.}A^{-.})-\omega(DA)\}-\...
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0 answers
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How is relative interaction energy defined and quantified?

I understand the interaction energy is the energy associated or caused by the interaction between the objects. So, for atoms it has to be the sum of van der Waals interaction and Coulomb interaction. ...
1 vote
0 answers
45 views

What happens inside the orbital when energy provided to electron is not sufficient for it to change orbitals? [closed]

While studying the chapter called Atomic Structure, we were introduced with Bohr's model of an Atom. Even though not all of his postulates were right, I believe some were. A doubt arose in the ...
-4 votes
1 answer
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why can water heated to a certain temperature in microwave explode when removing cup , bowl etc to room temperature air? [closed]

Studied a lot about $\mathrm{pH}$ , molecule dipoles properties $\ce{H2O}$. never saw anything along lines of energy storage, except ice contains heat energy , ionization of water always happens. ...
1 vote
0 answers
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Saturated vapor and liquid densities (VLC curve) from Helmholtz free energy equation of state

I have been reading about the statistical associating fluid theory (SAFT) which computes the Helmholtz free energy ($A$) from the SAFT EoS (a hell lot of equations) for a molecule of interest, and is ...
0 votes
0 answers
50 views

Nanoscale hydrogen batteries that use water-splitting technology

It was claimed in this article in 2019 that a nano-battery using water splitting technology is developed. It is described as: The battery gains its charge by interacting with water molecules present ...
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Will increasing the temperature of solid reactants increase rate of reaction?

When temperature of aqueous and gaseous reactants increase, the rate of reaction increases since the particles will move more quickly so frequency of effective collision increases. But does this work ...
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How to interpret the “surface power density” of a battery/capacitor

I’ve come across this research and one point of representing a power output confuses me: This enzymatic fuel cell is based on non-immobilized enzymes that exhibit a maximum power output of $\pu{0.8 ...
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1 vote
0 answers
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Synthesis of Jet Fuel from Fe-Mn-K Catalyst using Atmospheric CO2 [closed]

I wanted to do some back of the hand math on how many nuclear reactors it would take to reduce CO2 in the atmosphere to pre industrial levels after reading the article below describing the process. ...
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1 answer
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Is each bag of plastic a polymer/macromolecule? If yes, why does it tear so easily? [duplicate]

For example, polyethene is a macromolecule. So each bag of polyethene should be one molecule. Doesn't tearing it therefore involve breaking strong covalent bonds? Shouldn't the energy needed to do ...
3 votes
1 answer
141 views

Size and maximal power output of a battery of electrochemical reactions

For a battery working and chargeable on electrochemical reaction, how does the size of the battery affect its maximal power output? Specifically, With any chemicals/materials available and current ...
0 votes
0 answers
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How can energy be gained from oxidative deamination?

In (most cases of) degradation of amino acids, the process start with the amino group being transferred to $\alpha$-ketoglutarare, replacing its keto group. This turns $\alpha$-ketoglutarare into ...
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Rate of Decomposition of Sodium Thiosulphate

I want to calculate the activation energy of the decomposition of sodium thiosulphate, as a part of my school research project. I am aware that I must use the Arrhenius equation where the rate of ...
2 votes
0 answers
101 views

How to compare the Leonard-Jones potential energy curves of diatomic molecules?

The graph shows the dependence of potential energy on internuclear or intermolecular distance according to the L-J model, but how to compare lennard-jones potential energy curves of diatomic molecules,...
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0 answers
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Is the heat (or work) of the system always equal and opposite to that of the surroundings?

I know energy must always be conserved by the first law of thermodynamics, but is there ever a scenario in which a system say releases some amount of energy as work, and the surroundings gains equal ...

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