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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How much energy does hydrogen gas contains per liter compared to kerosene? [closed]

When searched for this in Google, it says Diesel has an energy density of 45.5 megajoules per kilogram (MJ/kg), slightly lower than gasoline, which has an energy density of 45.8 MJ/kg. By contrast, ...
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Resource estimate for ab initio calculation

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 ...
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What is the order of reaction of the reaction between aqueous ammonium chloride and aqueous sodium hydroxide? [closed]

1 NH4CL (aqueous, 25% weight by volume)) + 1 NAOH (aqueous, 50% weight by volume) + 30.56 kilojoules of energy → 1 NH3 (gas) + 1 H2O (liquid) + 1 NACL (aqueous). What's the activation energy of this ...
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2 answers
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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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Which is chemical reaction has the highest energy density? [duplicate]

Lets say X and Y react to form XY, and release E Joules of energy in total, not per mole. If molar weight of X is 1 g and Y is 2 g So the energy density is 1000E/3 J/Kg. Which chemical reaction has ...
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-3 votes
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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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 ...
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1 answer
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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 ...
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-2 votes
1 answer
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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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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 ...
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3 votes
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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?...
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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 ...
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-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
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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 ...
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1 answer
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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
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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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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 ...
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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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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 ...
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6 votes
1 answer
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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 ...
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1 vote
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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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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. ...
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1 vote
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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 ...
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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. ...
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1 vote
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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 ...
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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
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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 ...
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3 votes
1 answer
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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 ...
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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 ...
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2 votes
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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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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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1 vote
1 answer
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example of endothermic luminescence?

Someone posed an interesting question to me the other day: is all production of light accompanied by the generation of heat? I have found that the question as posed invites vague answers, so I thought ...
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0 votes
1 answer
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Why is the Gibbs free energy of a reversible reaction not always 0? [duplicate]

From my understanding, reversible proceses are those where the expression: $$\Delta S_\mathrm{total} = \Delta S_\mathrm{system} + \Delta S_\mathrm{surroundings} = 0$$ is true for all for the entire ...
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1 vote
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How can G3P oxidize into 1,3-BPG without energy expenditure?

In glycolysis, one of the important steps is when Glyceraldehyde-3-phosphate is oxidized to 1,3- Bisphosphoglycerate, while reducing $NAD^+$ to NADH and $H^+$. I'm a bit perplexed by this step since ...
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Why is the transition state the highest energy point? [closed]

If partial bonds form during transition state, it means some energy is released, so how can it have the highest energy? Shouldn't the point before transition state be highest energy? (the point where ...
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Energy of reactants and products [closed]

In some reactions, energy is released and when I want to understand the reason for the release of energy, I find that the energy of the products is lower than that of the reactants. But What is this ...
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How to make my water destillery most effective?

I got a destillery for water with a capacity of 10l and a get the most of a spiral cooler in a 1l cooling pot mounted on top. I'm happy with the efficiency, however there's always room for improvement ...
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2 votes
0 answers
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Why does the PE becomes negative in potential energy versus intermolecular distance graph? [closed]

In the potential energy versus inter molecular distance graph, we know that atoms/molecules/particles want to be at optimum distance from each other ie $r_0$ and to the left of this position in the ...
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2 votes
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Does a larger bond energy in reactants mean a more exothermic reaction?

In the book "Combustion Physics" for C.K Law, page 42, it is stated that: The parameter that has the next strongest influence on [adiabatic flame temperature] $T_{ad}$ is the $C/H$ ratio of ...
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Lithium Air vs Li Fluoride battery capacity [closed]

Lithium air aka lithium oxygen batteries are described as highest theoretical capacity battery possible. In wikipedia, it says lithium air has energy density 5210 Watt hour per kg, including weight of ...
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Finding Potential Depth of Multiple-Minimum in a PEC

Suppose we have the following curve with more than one well and different maximum points: My simple question is how to calculate the potential depth of each well? Do we calculate all the potential ...
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Why is effective nuclear charge used to explain the periodicity of size of atoms and ions?

Why is effective nuclear charge used for explaining the periodicity of size of atoms and ions, even though radius depends upon many other factors? The size of $\ce{Na+}$ is smaller than that of $\ce{...
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5 votes
1 answer
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How can a hydrogen atom ever emit an X-ray photon?

From Scientific American, February 2014: The Proton Radius Puzzle: ...we had to tune the laser so that it came in with exactly the right amount of energy. The atom would make the jump to the higher ...
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2 votes
1 answer
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What is the average distance between electron 'shells' in an atom? Or between the innermost shell and the nucleus? [closed]

Somehow, I've never come across any mention of the actual, physical distances between, say the 1s and 2s shells in an atom, whether large or small.... I know that p, d and f (and g?) shells are oddly ...
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