Questions tagged [energy]
For questions relating to the energy required for or produced by reactions, including questions of endothermicity/exothermicity, bond enthalpy, etc.
593
questions
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1answer
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Why is it that protons and electrons undergo the same amount of deflection in an electric field if they have the same energy?
The question I have is with respect to this diagram. Which depicts a stream of protons and electrons entering a proton field with equal energy.
Why is it that in the case where the energy of protons ...
3
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0answers
20 views
Can someone help me understand the motivation behind and visualize the dihedral potential and the Urey-Bradley potential?
I am studying statistical mechanics and force-fields, and I see a lot of this formula being thrown around with no explanation:
$$U_{\mathrm{dihedral}} = \begin{cases}
k(1+\cos (n\psi + \phi)),&...
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votes
0answers
22 views
Does pressure x volume = kinetic energy?
Sorry don't know if this is more for physics or here, essentially I had a question on the root mean square velocity of gas particles equation and didn't know what it was so tried to work something ...
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2answers
55 views
Why electrons do not distribute evenly among the atoms in a molecule?
I was wondering why the state where electrons are evenly (or the closest to being evenly) distributed among the atoms in a molecule is not the lowest energy state? For example, in a water molecule it ...
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0answers
25 views
Energy of valence electrons [closed]
I am currently studying Electrical Engineering and I have this question:
An energy band is formed by the overlapping of atomic orbitals of atoms coming close to each other. I suspect that if the ...
2
votes
1answer
37 views
Why does higher temperature affect the rate of electrolysis?
I understand that more heat energy= higher rate of electrolysis, but can someone explain using higher-level terms why this occurs and if there are any theories or rules that explain this?
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0answers
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How can I determine whether sp-mixing occurs for heteronuclear diatomics?
I'm trying to draw out the molecular orbital diagram of nitrogen monoxide (NO) but I do not know whether sp-mixing occurs. This is important in order to determine the arrangement of molecular orbitals....
0
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1answer
27 views
How to interpret this formula about hydrogen bond energy
I want to evaluate some chemistry related formulas, which I don't understand.
In proteins, hydrogen bonding often occurs between the oxo group = O oxygen of one amino acid and the Ī±-amino group (N ā H)...
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vote
0answers
25 views
Are all exergonic reactions spontaneous?
Exergonic reactions have a negative $\Delta G$: the system loses free energy. Spontaneous reactions are also defined in the same way, as far as I know. Does this mean the two are synonymous?
There are ...
1
vote
1answer
150 views
Can vapour pressure be used to 'generate' work for free?
Given a bottle of water, a closed system, some of the water molecules in the liquid phase will have enough energy to escape that phase, forming water vapour, contributing to vapour pressure.
Now ...
0
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0answers
37 views
Can the energy used required to break a molecular bond of plastic (e.g. - PVC) be used to dissociate plastics into its constituent elements?
Dear Molecular Chemists and Physicists,
Pardon my ignorance, but why can not plastic polymers be broken down into their constituent elements?
Common bond energies are shown in these two separate ...
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votes
1answer
27 views
Why use enthalpy?
I learned that Enthalpy is useful because it can be used to see the heat flow. But base on the formula, enthalpy change only equals to heat flow when in constant pressure. If the pressure is non-...
3
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1answer
69 views
Strength of the hydrophobic interaction
How strong is the "hydrophobic force"?
Hydrophobic interactions are weak interactions but can have greater strength than hydrogen bonds. I find the strength of the hydrogen bond in ...
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votes
1answer
51 views
Stability of an atom in absence of EM field
According to Bohr model of atom, electrons move up an energy level in presence of EM field and emit a photon moving down the level.
In complete absence of any external EM field, shouldn't the electron ...
1
vote
1answer
29 views
Why constant volume combustion gives higher energy than constant pressure?
I have noticed when I have done some combustion equilibrium that enthalpy is higher when doing a constant volume combustion than pressure constant combustion.
Why is it so ? What are the reasons ...
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votes
1answer
17 views
Finding Gibbs energy at different temperatures just given Gibbs energy at one temperature
How would it be found the Gibbs energy at a certain temperature, if they just give you another Gibbs energy at a temperature? For example: Given $\Delta G = -230 Kcal/mol$ at $773K$ for the reaction $...
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votes
1answer
47 views
Why does Delta H change when the coefficients change in a reaction?
So I understand that if twice as much of the reactants are present, then twice as much energy is released. But isnāt the energy released per mole of reactant still the same? You are just scaling up ...
14
votes
3answers
528 views
Why do electrons jump back after absorbing energy and moving to a higher energy level?
Electrons in a shell absorb energy and move to higher energy levels, but they release their energy and jump back to the shell they originally were in. Why do they jump back? Why can they not keep ...
3
votes
3answers
111 views
Work done in expanding a gas reversibly and irreversibly
So, my chemistry teacher gave the class following $P_{external}$ versus $Volume$ diagrams for reversible and irreversible expansion of a gas which are as follows.
(Reversible expansion)
(...
0
votes
1answer
45 views
What is change in internal energy of a system in which combustion occurs at constant temperature?
We got a question in a test, in which we were asked which system has zero change in internal energy and it had an option which was combustion of methane at constant temperature. I imagined this to be ...
2
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0answers
73 views
A thermodynamics problem with an interesting equilibrium condition
Usually, when we analyze reactions, we assume that the reaction takes place at constant pressure or at constant volume. But there is no reason to assume this is generally the case, and so my friend ...
0
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1answer
52 views
A lot of confusion in 1st law of thermodynamics [closed]
My sir told me that Total energy of system = K.E + P.E in starting.
Then Change in energy = F(External force on body ) * displacement of walls.
Then from here , change in energy = W+q.
(Donāt ...
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0answers
27 views
Help in understanding first way of changing the state of system
There is a statement in my book:
THERMODYNAMICS
One way: We do some mechanical work, say $\pu{1 kJ},$ by rotating a set of small paddles and thereby churning water. Let the new state be called $\...
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0answers
24 views
Finding excited stage of electron from its potential energy
The potential energy of an electron in the hydrogen atom is $\pu{-6.8 eV}.$ Indicate the excited stage in which electron is present.
Total energy would be equal to $\pu{-3.4 eV}.$
I used the formula
$...
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0answers
20 views
Where can I find the released combustion energy in NASA CEA rocket problem?
I am using NASA CEA program for a study project.
I have read the CEA Nasa user's manual over and over, yet I haven't found an answer to my question which is :
where can I found in the output of NASA ...
0
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1answer
45 views
Is there an actual specific heat for aluminum in its gaseous state? [closed]
I've scourged the internet and I can't seem to find it anywhere although I've found the specific heat values for aluminum in both solid and liquid states. I'm trying to construct a heating curve and I ...
3
votes
1answer
91 views
Why does the CāH bond dissociation energy vary in a homologous series of primary alcohols?
Specifically, for the primary carbon atom in the alcohol. Here is bond dissociation energy (BDE) data from chapter three of Luo's Comprehensive handbook of chemical bond energies [1] (boldface refers ...
7
votes
2answers
808 views
What are high-energy electrons?
I read that (in cellular respiration) the transported electrons in NADH have a higher energy than those in FADH2.
I can't find a (simple or otherwise) explanation of what a "high-energy" ...
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votes
1answer
38 views
Question to find increment in total energy of a sample of He gas? [closed]
If a closed rigid wall container filled with 20 gram of Helium gas moving at a constant speed of 10 m/sec is stopped abruptly to stand still, find the increment in temperature of this He sample.
Way I ...
2
votes
1answer
112 views
How does heat transfer between molecules happen in deep?
Inside the container is cold water and outside the container is hot water. B is the microscopic view of container walls .W is water
And A is hot water.
What I have shown is the microscopic view of ...
1
vote
0answers
26 views
What is the fundamental difference between temperature and energy? [duplicate]
We know that temperature is proportional to the average kinetic energy of a system. We also know that temperature is not the same as energy because the temperature is intensive while the temperature ...
0
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0answers
37 views
Is heat a form of energy or is it just a transport of energy, not energy itself?
In every textbook I read, it says that heat is a form/type of energy... but in lecture, my professor said, that there is no such energy as heat and that heat is just a method by which we can transport ...
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vote
1answer
44 views
Modeling activation energy function
I'm quite new to the field, and actually am a mathematician. I was wondering if there is a way to model (find the equation of) the reaction progress (more specifically, the activation energy functions)...
0
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1answer
89 views
Why does activation energy depend on temperature? [duplicate]
To me it makes sense that the activation energy $E_\mathrm a$, as given by the Arrhenius equation, doesn't depend on the temperature as the needed energy (potential energy) to start a reaction has ...
0
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0answers
57 views
How can reversible reactions be exothermic or endothermic?
So this may be a dumb question, but because the forward reaction of a reversible reaction releases the sane amount of energy as the backwards reaction absorbs (because the bonds that are formed from ...
1
vote
1answer
75 views
Why does lattice enthalpy decrease with increasing ionic size?
Lattice enthalpy decreases as ions get larger, but I have found two explanations:
The charge density is greater in smaller ions, so greater attraction
The ions are themselves able to get closer ...
-2
votes
1answer
70 views
Is hypervalency a real thing? [duplicate]
I saw a proper debate going on between answers to a question about whether the octet rule could be violated. Some people were pointing to hypervalency in period 3 elements, due to the available d-...
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votes
2answers
295 views
Why energy is released when an electron is added to a neutral atom? [duplicate]
Question :
Why energy changes when an electron is added to a neutral atom?
1
vote
1answer
51 views
Can chemical energy from food be stored in a battery? [closed]
Suppose you built a machine that digested food in a similar way as humans do. Would it be possible, in principle, to extract the chemical energy from the digested food, turn it into electricity, and ...
0
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1answer
216 views
Does exchange energy affect completely filled orbitals?
In my textbook, it's written that exchange energy stabilises half filled and completely filled orbitals. But my teacher said electrons can't be exchanged in full filled orbitals because of pairing up ...
7
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3answers
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Can carbon dioxide be reduced to carbon monoxide and oxygen to produce energy?
There are lots of questions about reducing or burning CO2 to carbon and oxygen to solve climate change, but of course that wouldn't work because it takes a lot of energy. But carbon monoxide is more ...
0
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0answers
51 views
Arrhenius Equation : Interpretation
Consider the relation:
$$E_{Activation}=E_{Threshold} - E_{Avg}$$
Here the $E_{Avg}$ refers to the Potential Energy of the reactants. Now in order of meet $E_{Threshold}$ , the molecules must have ...
0
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0answers
36 views
Arrhenius equation - Proper Interpretation of Activation Energy term
Consider the normal form of Arrhenius Equation:$$k=Ae^{-\frac {E_a}{RT}}$$
The term, $e^{-\frac {E_a}{RT}}$, is interpreted as the fraction of molecules having energy greater than Activation Energy.
...
5
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2answers
263 views
Why Does Activation Energy not change with Temperature change
As The Graph Shows; $E_a$ (Activation Energy) = Energy Of transition State(Threshold Energy) $-$ Energy of Reactants.
So let This be the graph at Temperature $T_1$, Now say We Increase The Temperature ...
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0answers
28 views
Why do internal energy/heat and enthalphy differ? What is the physical significance of the $PV$ term for enthalphy of an ideal gas? [duplicate]
Let it be noted that this is not a duplicate of this downvoted-to-hell question, simply because I hope to ask it better!
I've been reading a thermo textbook and I've got a simple question.
The ...
4
votes
1answer
99 views
How is resonance energy measured?
Is it the difference of energies of formation of the resonance hybrid and the average of the energy of formation of all the contributing structures? How would we even calculate the energy of a ...
0
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1answer
34 views
Comparison of energy release from different types of fuels [closed]
I've recently been reading about the different amount of energy release for different types of fuels/hydrocarbons.
Anyways, I was wondering why butanol would release more energy (kj/mol) than methanol?...
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0answers
31 views
I calculated internal energy at various temperatures and pressures. My results differ from someone else's. Is this OK?
I would like to make sure that my understanding of internal energy is correct. I'm not a thermodynamicist, so apologies in advance for what is probably a basic question.
I previously calculated ...
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2answers
81 views
How do you know what elements will bond in a reaction? [closed]
I know all about the types of reactions, synthesis, decomp. etc., but when a bond is broken, how do you know that the free element will bond to another molecule?
Is it because that element has a ...
6
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0answers
78 views
Solving the Schrödinger equation for a rotating triatomic linear molecule
This source is showing that solving the Schrƶdinger equation for a triatmoic linear molecule yields the same formula for the rotationaI quantum states $BJ(J+1)$ as for dipoles.
For dipoles, the total ...
