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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3answers
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Does any element have nutritional (caloric) value?

Is there any single element (e.g. possibly carbon) that can be eaten, which has nutritional value in that it provides calories? I found on Wikipedia that http://en.wikipedia.org/wiki/Dietary_element ...
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1answer
3k views

Why are noble gases stable? [duplicate]

Generally, noble gases are very unreactive. Why? I understand that it has to do with electron shielding prospective electrons that could join the atom or leave and the energies associated with both ...
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1answer
6k views

What are some good research topics for a high school student?

I absolutely love chemistry and I really want to take part in science fairs. I am also taking an AP chemistry class. Cleaner fuel and energy sources and air pollution (especially due to smog and ...
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24 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
84 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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2answers
98 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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0answers
35 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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28 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 ...
5
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1answer
140 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
24 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
2k views

How do I balance the combustion reaction of butene?

I have butene being burned in a fuel rich engine and I can't seem to balance this reaction: $$\ce{C4H8 + $a$(O2 + 3.76 N2) -> $b$ CO2 + $c$ H2O + $d$ C4H8 + $e$ (3.76 N2)}$$ When I try write ...
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1answer
57 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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1answer
315 views

Does liquids that emit light when vibrated exist?

I am looking for a liquid that illuminates when vibrations are added. It does not have to be strictly chemical, it might as well be something else as well. Maybe a crystal in powder form mixed with ...
4
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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
6k views

How hot is elephant toothpaste?

So, I remember in high school chemistry when my teacher combined hydrogen peroxide with potassium iodide and it exploded into a yellowish foam. He said it was an exothermic reaction so it's really hot....
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1answer
52 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
83 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 ...
5
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1answer
135 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
43 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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0answers
51 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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0answers
30 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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0answers
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
2k views

Safe yet strong exothermic reaction?

I'm studying chemical engineering at uni (Belgium), and this year (my 2nd) we have to develop and build a stirling engine. It has to be powered by a relatively safe exothermic reaction (not dangerous ...
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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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2answers
113 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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7answers
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Why is the 2s orbital lower in energy than the 2p orbital when the electrons in 2s are usually farther from the nucleus?

My chemistry book explains that even though electrons in the $\mathrm{2p}$ orbital are closer to the nucleus on average, electrons from the $\mathrm{2s}$ orbital spend a very short time very close to ...
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1answer
1k views

How does ice melt?

I know that when water freezes, it forms a crystalline structure created by the hydrogen bonds between polar water molecules. Also, I know that during a phase change, the potential energy of the ...
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3answers
851 views

Is most of the weight you lose actually released as carbon dioxide when you exhale?

I've heard that most of the weight you "lose" is actually carbon dioxide released when you exhale. In percent its much more than what is released in pure heat energy and feces. Does anyone have ...
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0answers
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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21 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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2answers
66k views

Does the potential energy increase when temperature is raised?

The potential energy of a material is its ability to do work. So I would suspect the potential energy to increase during phase changes that increase entropy (solid $\rightarrow$ liquid and liquid $\...
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1answer
38 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
5k views

Bond dissociation energy order for C−C, N−N, O−O and F−F single bonds

Data from Chemistry LibreTexts — Strength of Covalent Bonds, Table 8.8.1: Average Bond Energies (kJ/mol) for Commonly Encountered Bonds at 273 K: $$ \begin{array}{cr} \hline \text{Bond} & D/\pu{...
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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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1answer
37 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
89 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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0answers
58 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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0answers
28 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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1answer
13k views

How do I distinguish between internal energy and enthalpy?

I am finding it hard to distinguish between the two. Can someone explain the two terms and the difference between them? I tried learning from Wikipedia, but it said for both the above terms that it ...
3
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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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3answers
3k views

Can Rydberg constant be in joules?

In my textbook (Chemistry Part - I for Class XI published by NCERT), there is an equation for the energy of an electron in an energy state: $$E_n = -R_\mathrm H\left(\frac{1}{n^2}\right)$$ and there ...
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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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0answers
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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2answers
9k views

Why is there a difference in available energy in saturated vs. unsaturated fatty acids?

On Wikipedia it states: In cellular metabolism, unsaturated fat molecules contain somewhat less energy (i.e., fewer calories) than an equivalent amount of saturated fat. Can someone explain why ...
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0answers
20 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
63 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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0answers
27 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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4answers
4k views

How is chemical energy stored in carbon

I'm fairly new to chemistry, and I have a hard time understanding how chemical energy is stored in carbon (I'm aware that the question can be generalised to 'how is chemical energy stored', but I'm ...

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