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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17 views

Why is average bond enthalpy measured by homolytic fission?

Average bond enthalpy: the energy required for 1 mole of a specific gaseous bonds to undergo homolytic fission Why specifically homolytic fission? Is it to allow comparison, but if that were the case,...
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51 views

Difference between chemical energy and potential energy

I know that chemical energy is the potential energy stored in the arrangement of atoms within molecules. Forming new chemical bonds releases energy. what does potential energy mean? Is it the energy ...
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20 views

Meaning of chemical energy [duplicate]

I am trying to understand the meaning of chemical energy. I saw in my book that chemical energy is stored in the bonds of chemical compounds and when the bonds are untied the chemical energy increases....
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23 views

Change in temperature if salt is dissolved in water with different initial temperatures

I will mix a salt with room-temperature water and 8 degree Celsius water. Then I will compare the heat of solution with each other. Does the initial temperature of the water affect how much the heat ...
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15 views

Efficiency of H production from FeOOH catalist?

Research has recently found that FeOOH is 25 times better at hydrogen production than titanium dioxide. Today, a new electrolysis plant today delivers energy efficiency of around 80%. Is 25x the ...
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1answer
51 views

Endothermic or Exothermic [closed]

Is an endothermic reaction always endothermic at all conditions of pressure, temperature etc.? Similarly for exothermic... I mean is sign of ∆H always the same as sign of ∆H°? This might seem to be a ...
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1answer
123 views

Values for heat of reaction example

I am currently studying the textbook Mass Spectrometry, third edition, by Jürgen H. Gross. Chapter 2.4.3 Bond Dissociation Energies and Heats of Formation says the following: Energetics of $\ce{H}^\...
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1answer
44 views

Why are there so many different formulations for energy? When do I use each one? [closed]

I understand that energy is a fairly arbitrary concept, and that it completely depends on your definition of energy. So far in my class, we have discussed: Entropy, $S$ (not really energy, but it ...
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1answer
70 views

How to figure out the most stable conformation of the diastereomer?

I guess my main question is looking only at the newman projection how does one determine the stereochemistry? In the molecule to the right, I get for the first carbon, (et, H, Me,) R ( I flipped it ...
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26 views

energy vs reaction coordinate diagram [closed]

To know the energy values-marked as ? and the coordinates-x,y for a given reaction ...
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2answers
87 views

The hydration energy of NaCl is −774.3 kJ. Then why are we not able to harness that energy and run machines just by mixing salt in water? [closed]

The hydration energy of NaCl is −774.3 kJ. Then why are we not able to harness that energy and run machines just by mixing salt in water? Where does all the energy go which is released when we mix ...
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1answer
48 views

Regarding the infinitesimal form of the First Law of Thermodynamics

First Law of Thermodynamics is expressed as[1] The internal energy of an isolated system is constant. If $w$ denotes the work done on a system, $q$ for the energy transferred as heat to the system,...
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32 views

Effect of intramolecular hydrogen bonding on the stability of a molecule

What will be the effects of intramolecular hydrogen bonding on the stability of a molecule? Will it increase or decrease the overall stability of a molecule? Or will it not have any impact on the ...
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1answer
152 views

How to determine the relative contribution of resonance structures when different rules give contradictory outcomes?

In order to determine the relative contributions of resonance structures, my textbook gives the following rules (in order): The more covalent bonds a structure has, the higher it scores. Structures ...
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1answer
31 views

Energy in chemical reactions [closed]

My question concerns how energy is used in chemical reactions. I am working with a reaction between magnesium and hydrochloric acid in a class (although this is not a homework question). What I've ...
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1answer
29 views

Can dissipative work be circumscribed as irreversible heat transfer

My question refers to an article I read yesterday in which the author states that for the calculation of the entropy change for a process (in that case friction, during an irreversible adiabatic gas ...
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1answer
84 views

How to find the lifetime of sodium atoms in the 3p using information on the spectral line width?

I am trying to find the lifetime of sodium atoms at the 3p state using the relationship between the spectral linewidth and the uncertainty principle: $$ \Delta E \times \Delta t = h / 4\pi $$ The ...
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1answer
55 views

What are the assumption of Gibbs free energy equation referring to the system and the surrounding?

The system for $\mathrm dG=\mathrm dH-T\,\mathrm dS$ is a constant temperature and pressure throughout the process, only volume work is possible and it is in thermal equilibrium with the ...
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2answers
90 views

What are Degenerate Rotational Energy Levels Physically?

I'm in introductory chem, so I don't have much of the physical background to really understand what's going on yet, but we're learning about rotational energy levels, and how some rotational energy ...
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57 views

What is the significance of the downward arrows in energy level diagrams in organic chemistry?

The following text is from Solomons, Fryhle and Snyder Organic Chemistry Third Edition, chapter 1 "The Basics: Bonding and Molecular Structure", page 13, topic 1.5 "Resonance Theory", sub topic 1.5B "...
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2answers
102 views

How energy is released when chemical bond is formed?

In books it is commonly written that whenever a chemical bond is formed the energy of the molecules/atoms gets lowered and hence energy is released. This is generally explained by diagrams like this ...
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1answer
139 views

What are computed energies in DFT and FF methods relative to?

I am not talking about zero-point energy. I wish to understand how the energy of a system is calculated relative to a zero baseline. This is best explained with an example. From DFT, the energy ...
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1answer
47 views

Surface energy for different crystallographic planes

For a given crystal structure, say body centred cubic, on what factors does surface energy of each plane depend? A basic approach considers the atomic density on each crystallographic plane, the ...
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1answer
71 views

How to calculate the energy to dissociate a bond into neutral atoms?

I am self studying chemistry through MiT ocw 5.111 . On practice exam 2 problem 2 there is a question which states the following ...
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39 views

Is kinetic energy proportional to temperature for non-gases?

If the molecules in a sample of ice at $\pu{-15 °C}$ and $\pu{1 bar}$ all have their kinetic energy doubled, then what is the final phase? The answer is gas, but I am not sure how to get this answer. ...
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1answer
95 views

Why does aluminum chloride have a higher lattice energy than aluminum fluoride?

From the table below (source: McMurry's Chemistry [1, p. 212]), it is evident that $\ce{AlCl_3}$ has a higher lattice energy than $\ce{AlF3},$ even though $\ce{F}$ is smaller than $\ce{Cl}$. Why is ...
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2answers
115 views

Regarding units of water potential and chemical potential

If water potential is nothing but the chemical potential of a given solution, then why do their units differ? If the unit for the latter is taken as 'Energy per molecule' (which makes sense to me ...
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1answer
39 views

Ground state elevation for phase transition

I have a question about the illustration from chem.libretexts.org: the ground states of the liquid and gas are offset from that of the previous state by the heats of fusion and vaporization, ...
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79 views

Is it possible to have a negative overall activation energy for a whole reaction mechanism?

I am trying to find out correlation for ignition delay for alkane fuels. The activation energy part of the correlation gives me a negative value. For the ignition delay formulation, is it possible to ...
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22 views

Energy Levels of Molecular Orbitals formed by combination of Atomic Orbitals

In general when we talk about chemical bonding, we say that it is "nature's way to stabilize the systems" and the energy of the molecule formed by atoms will be lower than that of the individual atoms;...
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1answer
39 views

Why should we be interested in catalyst for electrolysis?

I've been reading papers on Phosphided metals (CoP, NiP, FeP) as a catalyst for electrolysis. They increase the current density of the cell for a voltage. If it still requires 39.4 kilowatt-hours ...
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1answer
55 views

Combustion of carbon with hydrogen [closed]

Can coal (carbon) be "burned" in a hydrogen atmosphere? I know it would not match the definition of "combustion". But is the reaction $$\ce{C +2H2 ->CH4}$$ exothermic? (I'm fairly convinced this ...
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38 views

Nuclear physics [closed]

When considering Fusion, the matter that gets converted into energy what specific matter is converted exactly like a quark and is most of the energy created from the matter turning into energy?
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1answer
93 views

How would one determine an element simply by looking at its binding energy?

I am self studying MIT OCW chemistry 5.111 2014, one of the lecture questions states the following: Consider a neutral atom with 8 distinct electron binding energies: −14 eV, −28 eV, −94 eV, −218 ...
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72 views

Literature value for the activation energy of the reaction between hydrochloric acid and sodium bicarbonate

Does anybody have the literature value for the activation energy of the reaction between hydrochloric acid and sodium bicarbonate? If yes, could you please cite the source for it and the value? I ...
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29 views

Electrons and Atomic Mass

Is the mass of electrons covered when talking about atomic mass. For example, the mass of Carbon is $12.011\space\text{amu}$. If this is including the mass of electrons (assuming the atom is neutral) ...
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2answers
65 views

Giving too much energy to an exothermic reaction [closed]

What will happen in an exothermic reaction if more than required energy is given? I mean, will it produce even more energy which will be highly dangerous or nothing will happen according to Le ...
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1answer
32 views

Is it possible to convert carbon soot/ black carbon in mg to CO2-equivalent? If so, how?

Since global warming is expressed in terms of carbon emissions or CO2 equivalent, can the short lived carbon soot/ black carbon that is produced from incomplete combustion be expressed in terms of CO2 ...
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19 views

Relative Energies of Resonance Contributors & Stability of Borazine

We know that Borazine (Inorganic Benzene) is aromatic in nature. The following image shows the resonance contributors of borazine: What are the relative energies of these three resonance contributors?...
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1answer
117 views

Energy cost of C−N rotation in hydroxamate group

I am looking for a literature reference on the energetic cost of C−N rotation in hydroxamate group such in LC5 in water. I have been googling for a while.
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21 views

Interlayer binding energy: how to convert to meV/Ų?

I've noticed that in most papers the interlayer binding energy is given in units of meV/Ų. But how do I get these units? Do I divide the interlayer binding energy I get by the area of my unit cell?
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2answers
66 views

Catalyst that combines oxygen and hydrogen

Are there any known catalysts that can combine hydrogen and oxygen into water? Does this type of reaction have a name? Trying to search for information, it seems to be all about splitting hydrogen ...
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28 views

Carbon Capture Absorption with Henry's Law

Assume the Henry’s coefficient for water at $\pu{20 °C}$ is $\pu{1.6E8 Pa}.$ What is the mole fraction of $\ce{CO2}$ that will be dissolved in water assuming that it is at equilibrium with a flue gas ...
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2answers
126 views

How is energy not stored in bonds? [duplicate]

Consider the paraphrase from Ebbing: It takes energy to break bonds & energy is released when bonds are formed Let's look at the first statement It takes energy to break bonds. Is this true ...
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1answer
68 views

Why does the Heisenberg uncertainty principle work in an atom? [closed]

Where is my logic wrong? An electron can only assume quantized energies in an atom. If an electron is localized in space in a hydrogen atom, its radius is known. If its radius is known, its ...
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63 views

eV and redox potential

I am trying to estimate the redox potential of an excited state as described in this reference. The paper says: The reduction potentials associated with the excited states cannot be directly ...
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36 views

Bond Dissociation Energy in Water [duplicate]

Why do the bond dissociation energies of the O−H bonds in water differ? Is it related to an increase in lone pair-bond pair repulsions upon the breaking of the first O−H bond (decrease in stability, ...
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73 views

What is the largest known zero-point energy for a molecule?

I was surprised to find out that the zero-point energy (ZPE) for the ground state of $\ce{BH3}$ is a few thousand $\pu{cm-1}$, because for molecules I usually work with, it's much smaller. Does anyone ...
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76 views

Does the activation energy depend upon the stoichiometric coefficient?

For the decomposition of $\ce{N2O5(g)}$ it is given that $$ \begin{align} \ce{2 N2O5(g) &→ 4 NO2(g) + O2(g)} &\quad\text{activation energy} &= E_\mathrm{a}\\ \ce{N2O5(g) &→ 2 NO2(...
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25 views

what is the bonding energy of I2 and I3-?

I need some information of bonding energy. I found that the bonding energy of $\ce{I2}$ is $\pu{151 kJ/mol}$ (https://www.chegg.com/homework-help/dimethyl-ether-ch3och3-ethanol-ch3ch2oh-constitutional-...

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